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Zhang J, Li F, Liu D, Liu Q, Song H. Engineering extracellular electron transfer pathways of electroactive microorganisms by synthetic biology for energy and chemicals production. Chem Soc Rev 2024; 53:1375-1446. [PMID: 38117181 DOI: 10.1039/d3cs00537b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2023]
Abstract
The excessive consumption of fossil fuels causes massive emission of CO2, leading to climate deterioration and environmental pollution. The development of substitutes and sustainable energy sources to replace fossil fuels has become a worldwide priority. Bio-electrochemical systems (BESs), employing redox reactions of electroactive microorganisms (EAMs) on electrodes to achieve a meritorious combination of biocatalysis and electrocatalysis, provide a green and sustainable alternative approach for bioremediation, CO2 fixation, and energy and chemicals production. EAMs, including exoelectrogens and electrotrophs, perform extracellular electron transfer (EET) (i.e., outward and inward EET), respectively, to exchange energy with the environment, whose rate determines the efficiency and performance of BESs. Therefore, we review the synthetic biology strategies developed in the last decade for engineering EAMs to enhance the EET rate in cell-electrode interfaces for facilitating the production of electricity energy and value-added chemicals, which include (1) progress in genetic manipulation and editing tools to achieve the efficient regulation of gene expression, knockout, and knockdown of EAMs; (2) synthetic biological engineering strategies to enhance the outward EET of exoelectrogens to anodes for electricity power production and anodic electro-fermentation (AEF) for chemicals production, including (i) broadening and strengthening substrate utilization, (ii) increasing the intracellular releasable reducing equivalents, (iii) optimizing c-type cytochrome (c-Cyts) expression and maturation, (iv) enhancing conductive nanowire biosynthesis and modification, (v) promoting electron shuttle biosynthesis, secretion, and immobilization, (vi) engineering global regulators to promote EET rate, (vii) facilitating biofilm formation, and (viii) constructing cell-material hybrids; (3) the mechanisms of inward EET, CO2 fixation pathway, and engineering strategies for improving the inward EET of electrotrophic cells for CO2 reduction and chemical production, including (i) programming metabolic pathways of electrotrophs, (ii) rewiring bioelectrical circuits for enhancing inward EET, and (iii) constructing microbial (photo)electrosynthesis by cell-material hybridization; (4) perspectives on future challenges and opportunities for engineering EET to develop highly efficient BESs for sustainable energy and chemical production. We expect that this review will provide a theoretical basis for the future development of BESs in energy harvesting, CO2 fixation, and chemical synthesis.
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Affiliation(s)
- Junqi Zhang
- Frontier Science Center for Synthetic Biology (Ministry of Education), Key Laboratory of Systems Bioengineering, and School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China.
| | - Feng Li
- Frontier Science Center for Synthetic Biology (Ministry of Education), Key Laboratory of Systems Bioengineering, and School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China.
| | - Dingyuan Liu
- Frontier Science Center for Synthetic Biology (Ministry of Education), Key Laboratory of Systems Bioengineering, and School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China.
| | - Qijing Liu
- Frontier Science Center for Synthetic Biology (Ministry of Education), Key Laboratory of Systems Bioengineering, and School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China.
| | - Hao Song
- Frontier Science Center for Synthetic Biology (Ministry of Education), Key Laboratory of Systems Bioengineering, and School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China.
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Tripathi S, Voogdt CGP, Bassler SO, Anderson M, Huang PH, Sakenova N, Capraz T, Jain S, Koumoutsi A, Bravo AM, Trotter V, Zimmerman M, Sonnenburg JL, Buie C, Typas A, Deutschbauer AM, Shiver AL, Huang KC. Randomly barcoded transposon mutant libraries for gut commensals I: Strategies for efficient library construction. Cell Rep 2024; 43:113517. [PMID: 38142397 DOI: 10.1016/j.celrep.2023.113517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Revised: 10/22/2023] [Accepted: 11/14/2023] [Indexed: 12/26/2023] Open
Abstract
Randomly barcoded transposon mutant libraries are powerful tools for studying gene function and organization, assessing gene essentiality and pathways, discovering potential therapeutic targets, and understanding the physiology of gut bacteria and their interactions with the host. However, construction of high-quality libraries with uniform representation can be challenging. In this review, we survey various strategies for barcoded library construction, including transposition systems, methods of transposon delivery, optimal library size, and transconjugant selection schemes. We discuss the advantages and limitations of each approach, as well as factors to consider when selecting a strategy. In addition, we highlight experimental and computational advances in arraying condensed libraries from mutant pools. We focus on examples of successful library construction in gut bacteria and their application to gene function studies and drug discovery. Given the need for understanding gene function and organization in gut bacteria, we provide a comprehensive guide for researchers to construct randomly barcoded transposon mutant libraries.
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Affiliation(s)
- Surya Tripathi
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Carlos Geert Pieter Voogdt
- Genome Biology Unit, EMBL Heidelberg, Meyerhofstraße 1, 69117 Heidelberg, Germany; Structural and Computational Biology Unit, EMBL Meyerhofstraße 1, 69117 Heidelberg, Germany
| | - Stefan Oliver Bassler
- Genome Biology Unit, EMBL Heidelberg, Meyerhofstraße 1, 69117 Heidelberg, Germany; Faculty of Biosciences, Heidelberg University, Grabengasse 1, 69117 Heidelberg, Germany
| | - Mary Anderson
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Po-Hsun Huang
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Nazgul Sakenova
- Genome Biology Unit, EMBL Heidelberg, Meyerhofstraße 1, 69117 Heidelberg, Germany
| | - Tümay Capraz
- Genome Biology Unit, EMBL Heidelberg, Meyerhofstraße 1, 69117 Heidelberg, Germany; Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Sunit Jain
- Chan Zuckerberg Biohub, San Francisco, CA 94158, USA
| | - Alexandra Koumoutsi
- Genome Biology Unit, EMBL Heidelberg, Meyerhofstraße 1, 69117 Heidelberg, Germany
| | - Afonso Martins Bravo
- Department of Fundamental Microbiology, University of Lausanne, 1015 Lausanne, Switzerland
| | - Valentine Trotter
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Michael Zimmerman
- Structural and Computational Biology Unit, EMBL Meyerhofstraße 1, 69117 Heidelberg, Germany
| | - Justin L Sonnenburg
- Chan Zuckerberg Biohub, San Francisco, CA 94158, USA; Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Cullen Buie
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Athanasios Typas
- Genome Biology Unit, EMBL Heidelberg, Meyerhofstraße 1, 69117 Heidelberg, Germany; Structural and Computational Biology Unit, EMBL Meyerhofstraße 1, 69117 Heidelberg, Germany.
| | - Adam M Deutschbauer
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, CA 94720, USA; Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
| | - Anthony L Shiver
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA.
| | - Kerwyn Casey Huang
- Chan Zuckerberg Biohub, San Francisco, CA 94158, USA; Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94305, USA; Department of Bioengineering, Stanford University, Stanford, CA 94305, USA.
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Zhu L, Song Y, Ma S, Yang S. Heterologous production of 3-hydroxypropionic acid in Methylorubrum extorquens by introducing the mcr gene via a multi-round chromosomal integration system based on cre-lox71/lox66 and transposon. Microb Cell Fact 2024; 23:5. [PMID: 38172868 PMCID: PMC10763676 DOI: 10.1186/s12934-023-02275-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Accepted: 12/14/2023] [Indexed: 01/05/2024] Open
Abstract
BACKGROUND AND AIM Reprogramming microorganisms to enhance the production of metabolites is a part of contemporary synthetic biology, which relies on the availability of genetic tools to successfully manipulate the bacteria. Methylorubrum extorquens AM1 is a platform microorganism used to convert C1 compounds into various value-added products. However, the repertoire of available plasmids to conveniently and quickly fine-tune the expression of multiple genes in this strain is extremely limited compared with other model microorganisms such as Escherichia coli. Thus, this study aimed to integrate existing technologies, such as transposon-mediated chromosomal integration and cre-lox-mediated recombination, to achieve the diversified expression of target genes through multiple chromosomal insertions in M. extorquens AM1. RESULTS A single plasmid toolkit, pSL-TP-cre-km, containing a miniHimar1 transposon and an inducible cre-lox71/lox66 system, was constructed and characterized for its multiple chromosomal integration capacity. A co-transcribed mcr-egfp cassette [for the production of 3-hydroxypropionic acid (3-HP) and a reporting green fluorescent protein] was added to construct pTP-cre-mcr-egfp for evaluating its utility in mediating the expression of heterologous genes, resulting in the production of 3-HP with a titer of 34.7-55.2 mg/L by two chromosomal integration copies. Furthermore, in association with the expression of plasmid-based mcr, 3-HP production increased to 65.5-92.4 mg/L. CONCLUSIONS This study used a multi-round chromosomal integration system based on cre-lox71/lox66 and a transposon to construct a single constructed vector. A heterologous mcr gene was introduced through this vector, and high expression of 3-hydroxypropionic acid was achieved in M. extorquens. This study provided an efficient genetic tool for manipulating M. extorquens, which not only help increase the expression of heterologous genes in M. extorquens but also provide a reference for strains lacking genetic manipulation vectors.
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Affiliation(s)
- Liping Zhu
- Shandong Province Key Laboratory of Applied Mycology, Qingdao International Center on Microbes Utilizing Biogas, School of Life Sciences, Qingdao Agricultural University, Qingdao, Shandong Province, People's Republic of China.
| | - Yazhen Song
- Shandong Province Key Laboratory of Applied Mycology, Qingdao International Center on Microbes Utilizing Biogas, School of Life Sciences, Qingdao Agricultural University, Qingdao, Shandong Province, People's Republic of China
| | - Shunan Ma
- Shandong Province Key Laboratory of Applied Mycology, Qingdao International Center on Microbes Utilizing Biogas, School of Life Sciences, Qingdao Agricultural University, Qingdao, Shandong Province, People's Republic of China
| | - Song Yang
- Shandong Province Key Laboratory of Applied Mycology, Qingdao International Center on Microbes Utilizing Biogas, School of Life Sciences, Qingdao Agricultural University, Qingdao, Shandong Province, People's Republic of China.
- Key Laboratory of Systems Bioengineering, Ministry of Education, Tianjin University, Tianjin, People's Republic of China.
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Xia M, Yu D, Chen H, Dai J, Gao N, Li S, Bi X, Qiu D. An RpoN-dependent PEP-CTERM gene is involved in floc formation of an Aquincola tertiaricarbonis strain. BMC Microbiol 2023; 23:20. [PMID: 36658495 PMCID: PMC9850573 DOI: 10.1186/s12866-022-02745-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Accepted: 12/21/2022] [Indexed: 01/20/2023] Open
Abstract
BACKGROUND The floc is a characteristic of microbial aggregate growth, displaying cloudy suspensions in water. Floc formation has been demonstrated in a series of bacteria and the floc-forming bacteria play a crucial role in activated sludge (AS) process widely used for municipal sewage and industrial wastewater treatment over a century. It has been demonstrated that some exopolysaccharide biosynthesis genes and the sigma factor (sigma54 or rpoN) were required for floc forming in some bacteria. However, the mechanism underlying the floc formation stills need to be elucidated. RESULTS In this study, we demonstrate that a TPR (Tetratricopeptide repeats) protein-encoding gene prsT is required for floc formation of Aquincola tertiaricarbonis RN12 and an upstream PEP-CTERM gene (designated pepA), regulated by RpoN1, is involved in its floc formation but not swarming motility and biofilm formation. Overexpression of PepA could rescue the floc-forming phenotype of the rpoN1 mutant by decreasing the released soluble exopolysaccharides and increasing the bound polymers. CONCLUSION Our results indicate that the wide-spread PEP-CTERM proteins play an important role in the self-flocculation of bacterial cells and may be a component of extracellular polymeric substances required for floc-formation.
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Affiliation(s)
- Ming Xia
- grid.411854.d0000 0001 0709 0000School of Life Sciences, Hubei Engineering Research Center for Protection and Utilization of Special Biological Resources in the Hanjiang River Basin, Jianghan University, Wuhan, 430056 China ,grid.411854.d0000 0001 0709 0000Hubei Key Laboratory of Environmental and Health Effects of Persistent Toxic Substances, Jianghan University, Wuhan, 430056 China
| | - Dianzhen Yu
- grid.410726.60000 0004 1797 8419University of Chinese Academy of Sciences, Beijing, 100049 China ,grid.419092.70000 0004 0467 2285Institute for Nutritional Sciences, SIBS, Chinese Academy of Sciences, Shanghai, 200031 China
| | - Han Chen
- grid.410726.60000 0004 1797 8419University of Chinese Academy of Sciences, Beijing, 100049 China ,grid.429211.d0000 0004 1792 6029Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072 Hubei Province China
| | - Jingcheng Dai
- grid.429211.d0000 0004 1792 6029Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072 Hubei Province China
| | - Na Gao
- grid.469521.d0000 0004 1756 0127Fisheries Research Institute, Anhui Academy of Agricultural Sciences, Hefei, 230031 China
| | - Shuyang Li
- grid.429211.d0000 0004 1792 6029Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072 Hubei Province China
| | - Xuezhi Bi
- grid.452198.30000 0004 0485 9218Bioprocessing Technology Institute, Agency for Science, Technology and Research, Singapore, 138668 Singapore
| | - Dongru Qiu
- grid.429211.d0000 0004 1792 6029Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072 Hubei Province China
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Sackett JD, Kamble N, Leach E, Schuelke T, Wilbanks E, Rowe AR. Genome-Scale Mutational Analysis of Cathode-Oxidizing Thioclava electrotropha ElOx9 T. Front Microbiol 2022; 13:909824. [PMID: 35756027 PMCID: PMC9226611 DOI: 10.3389/fmicb.2022.909824] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Accepted: 05/17/2022] [Indexed: 11/13/2022] Open
Abstract
Extracellular electron transfer (EET) – the process by which microorganisms transfer electrons across their membrane(s) to/from solid-phase materials – has implications for a wide range of biogeochemically important processes in marine environments. Though EET is thought to play an important role in the oxidation of inorganic minerals by lithotrophic organisms, the mechanisms involved in the oxidation of solid particles are poorly understood. To explore the genetic basis of oxidative EET, we utilized genomic analyses and transposon insertion mutagenesis screens (Tn-seq) in the metabolically flexible, lithotrophic Alphaproteobacterium Thioclava electrotropha ElOx9T. The finished genome of this strain is 4.3 MB, and consists of 4,139 predicted ORFs, 54 contain heme binding motifs, and 33 of those 54 are predicted to localize to the cell envelope or have unknown localizations. To begin to understand the genetic basis of oxidative EET in ElOx9T, we constructed a transposon mutant library in semi-rich media which was comprised of >91,000 individual mutants encompassing >69,000 unique TA dinucleotide insertion sites. The library was subjected to heterotrophic growth on minimal media with acetate and autotrophic oxidative EET conditions on indium tin oxide coated glass electrodes poised at –278 mV vs. SHE or un-poised in an open circuit condition. We identified 528 genes classified as essential under these growth conditions. With respect to electrochemical conditions, 25 genes were essential under oxidative EET conditions, and 29 genes were essential in both the open circuit control and oxidative EET conditions. Though many of the genes identified under electrochemical conditions are predicted to be localized in the cytoplasm and lack heme binding motifs and/or homology to known EET proteins, we identified several hypothetical proteins and poorly characterized oxidoreductases that implicate a novel mechanism(s) for EET that warrants further study. Our results provide a starting point to explore the genetic basis of novel oxidative EET in this marine sediment microbe.
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Affiliation(s)
- Joshua D Sackett
- Department of Biological Sciences, University of Cincinnati, Cincinnati, OH, United States
| | - Nitin Kamble
- Department of Biological Sciences, University of Cincinnati, Cincinnati, OH, United States
| | - Edmund Leach
- Department of Biological Sciences, University of Cincinnati, Cincinnati, OH, United States
| | - Taruna Schuelke
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Elizabeth Wilbanks
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Annette R Rowe
- Department of Biological Sciences, University of Cincinnati, Cincinnati, OH, United States
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Borchert AJ, Bleem A, Beckham GT. Experimental and Analytical Approaches for Improving the Resolution of Randomly Barcoded Transposon Insertion Sequencing (RB-TnSeq) Studies. ACS Synth Biol 2022; 11:2015-2021. [PMID: 35657709 PMCID: PMC9208016 DOI: 10.1021/acssynbio.2c00119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Randomly barcoded transposon insertion sequencing (RB-TnSeq) is an efficient, multiplexed method to determine microbial gene function during growth under a selection condition of interest. This technique applies to growth, tolerance, and persistence studies in a variety of hosts, but the wealth of data generated can complicate the identification of the most critical gene targets. Experimental and analytical methods for improving the resolution of RB-TnSeq are proposed, using Pseudomonas putida KT2440 as an example organism. Several key parameters, such as baseline media selection, substantially influence the determination of gene fitness. We also present options to increase statistical confidence in gene fitness, including increasing the number of biological replicates and passaging the baseline culture in parallel with selection conditions. These considerations provide practitioners with several options to identify genes of importance in TnSeq data sets, thereby streamlining metabolic characterization.
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Affiliation(s)
- Andrew J. Borchert
- Renewable Resources and Enabling Sciences Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United States
- Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, United States
| | - Alissa Bleem
- Renewable Resources and Enabling Sciences Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United States
- Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, United States
| | - Gregg T. Beckham
- Renewable Resources and Enabling Sciences Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United States
- Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, United States
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7
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Gao N, Dai J, Liu Y, Li S, Wang J, Lu W, Qiu D. Cellulose-mediated floc formation by the activated sludge bacterium Shinella zoogloeoides ATCC 19623. BMC Microbiol 2022; 22:104. [PMID: 35421928 PMCID: PMC9012009 DOI: 10.1186/s12866-022-02516-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2021] [Accepted: 03/28/2022] [Indexed: 11/26/2022] Open
Abstract
Background Bacterial floc formation plays a central role in the activated sludge (AS) process. The formation of AS flocs has long been known to require exopolysaccharide biosynthesis. We had demonstrated that both expolysaccharides and PEP-CTERM (a short C-terminal domain includes a near-invariant motif Pro-Glu-Pro (PEP)) proteins were required for floc-forming in Zoogloea resiniphila MMB, a dominant AS bacterium. However, the PEP-CTERM proteins are not encoded in the genome of AS bacterium Shinella zoogloeoides ATCC 19623 (formerly known as Zoogloea ramigera I-16-M) and other sequenced AS bacteria strains. The mechanism underlying floc formation of Shinella and related AS bacteria remained largely unclear. Results In this study, we have sequenced and annotated the complete genome of S. zoogloeoides ATCC 19623 (aka I-16-M), previously isolated in USA and treated as the neotype for the AS floc-forming bacterium Zoogloea ramigera I-16-M, and another AS strain XJ20 isolated in China. Mariner transposon mutagenesis had been conducted to isolate floc-forming-deficient mutants in the strain ATCC 19623 as previously performed by using Tn5 transposon three decades ago. The transposon insertional sites of multiple mutants were mapped to the gene cluster for bacterial cellulose synthesis (bcs) and secretion, and the role played by these genes in floc-formation had been further confirmed by genetic complementation. Interestingly, the restriction map of this bcs locus-flanking region was highly similar to that of the previously identified DNA fragment required for floc-formation in 1980s. Cellulase treatment abolished the floc-forming phenotype of S. zoogloeoides ATCC 19623 but not that of Z. resiniphila MMB strain. The FTIR spectral analyses revealed that the samples extracted from S. zoogloeoides ATCC 19623 were cellulose polymer. Conclusion Our results indicated that we have largely reproduced and completed the unfinished pioneering work on AS floc-formation mechanism, demonstrating that the floc-formation and flocculating capability of Shinella were mediated by extracellular cellulose polymers. Supplementary Information The online version contains supplementary material available at 10.1186/s12866-022-02516-y.
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The RNA-Binding Protein ProQ Impacts Exopolysaccharide Biosynthesis and Second Messenger Cyclic di-GMP Signaling in the Fire Blight Pathogen Erwinia amylovora. Appl Environ Microbiol 2022; 88:e0023922. [PMID: 35416685 DOI: 10.1128/aem.00239-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Erwinia amylovora is a plant-pathogenic bacterium that causes fire blight disease in many economically important plants, including apples and pears. This bacterium produces three exopolysaccharides (EPSs), amylovoran, levan, and cellulose, and forms biofilms in host plant vascular tissues, which are crucial for pathogenesis. Here, we demonstrate that ProQ, a conserved bacterial RNA chaperone, was required for the virulence of E. amylovora in apple shoots and for biofilm formation in planta. In vitro experiments revealed that the deletion of proQ increased the production of amylovoran and cellulose. Prc is a putative periplasmic protease, and the prc gene is located adjacent to proQ. We found that Prc and the associated lipoprotein NlpI negatively affected amylovoran production, whereas Spr, a peptidoglycan hydrolase degraded by Prc, positively regulated amylovoran. Since the prc promoter is likely located within proQ, our data showed that proQ deletion significantly reduced the prc mRNA levels. We used a genome-wide transposon mutagenesis experiment to uncover the involvement of the bacterial second messenger c-di-GMP in ProQ-mediated cellulose production. The deletion of proQ resulted in elevated intracellular c-di-GMP levels and cellulose production, which were restored to wild-type levels by deleting genes encoding c-di-GMP biosynthesis enzymes. Moreover, ProQ positively affected the mRNA levels of genes encoding c-di-GMP-degrading phosphodiesterase enzymes via a mechanism independent of mRNA decay. In summary, our study revealed a detailed function of E. amylovora ProQ in coordinating cellulose biosynthesis and, for the first time, linked ProQ with c-di-GMP metabolism and also uncovered a role of Prc in the regulation of amylovoran production. IMPORTANCE Fire blight, caused by the bacterium Erwinia amylovora, is an important disease affecting many rosaceous plants, including apple and pear, that can lead to devastating economic losses worldwide. Similar to many xylem-invading pathogens, E. amylovora forms biofilms that rely on the production of exopolysaccharides (EPSs). In this paper, we identified the RNA-binding protein ProQ as an important virulence regulator. ProQ played a central role in controlling the production of EPSs and participated in the regulation of several conserved bacterial signal transduction pathways, including the second messenger c-di-GMP and the periplasmic protease Prc-mediated systems. Since ProQ has recently been recognized as a global posttranscriptional regulator in many bacteria, these findings provide new insights into multitiered regulatory mechanisms for the precise control of virulence factor production in bacterial pathogens.
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Prochlorococcus Exudate Stimulates Heterotrophic Bacterial Competition with Rival Phytoplankton for Available Nitrogen. mBio 2022; 13:e0257121. [PMID: 35012332 PMCID: PMC8749424 DOI: 10.1128/mbio.02571-21] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The marine cyanobacterium Prochlorococcus numerically dominates the phytoplankton community of the nutrient-limited open ocean, establishing itself as the most abundant photosynthetic organism on Earth. This ecological success has been attributed to lower cell quotas for limiting nutrients, superior resource acquisition, and other advantages associated with cell size reduction and genome streamlining. In this study, we tested the prediction that Prochlorococcus outcompetes its rivals for scarce nutrients and that this advantage leads to its numerical success in nutrient-limited waters. Strains of Prochlorococcus and its sister genus Synechococcus grew well in both mono- and cocultures when nutrients were replete. However, in nitrogen-limited medium, Prochlorococcus outgrew Synechococcus but only when heterotrophic bacteria were also present. In the nitrogen-limited medium, the heterotroph Alteromonas macleodii outcompeted Synechococcus for nitrogen but only if stimulated by the exudate released by Prochlorococcus or if a proxy organic carbon source was provided. Genetic analysis of Alteromonas suggested that it outcompetes Synechococcus for nitrate and/or nitrite, during which cocultured Prochlorococcus grows on ammonia or other available nitrogen species. We propose that Prochlorococcus can stimulate antagonism between heterotrophic bacteria and potential phytoplankton competitors through a metabolic cross-feeding interaction, and this stimulation could contribute to the numerical success of Prochlorococcus in nutrient-limited regions of the ocean. IMPORTANCE In nutrient-poor habitats, competition for limited resources is thought to select for organisms with an enhanced ability to scavenge nutrients and utilize them efficiently. Such adaptations characterize the cyanobacterium Prochlorococcus, the most abundant photosynthetic organism in the nutrient-limited open ocean. In this study, the competitive superiority of Prochlorococcus over a rival cyanobacterium, Synechococcus, was captured in laboratory culture. Critically, this outcome was achieved only when key aspects of the open ocean were simulated: a limited supply of nitrogen and the presence of heterotrophic bacteria. The results indicate that Prochlorococcus promotes its numerical dominance over Synechococcus by energizing the heterotroph's ability to outcompete Synechococcus for available nitrogen. This study demonstrates how interactions between trophic groups can influence interactions within trophic groups and how these interactions likely contribute to the success of the most abundant photosynthetic microorganism.
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The Signaling Pathway That cGAMP Riboswitches Found: Analysis and Application of Riboswitches to Study cGAMP Signaling in Geobacter sulfurreducens. Int J Mol Sci 2022; 23:ijms23031183. [PMID: 35163114 PMCID: PMC8835794 DOI: 10.3390/ijms23031183] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Revised: 01/12/2022] [Accepted: 01/14/2022] [Indexed: 02/03/2023] Open
Abstract
The Hypr cGAMP signaling pathway was discovered via the function of the riboswitch. In this study, we show the development of a method for affinity capture followed by sequencing to identify non-coding RNA regions that bind nucleotide signals such as cGAMP. The RNAseq of affinity-captured cGAMP riboswitches from the Geobacter sulfurreducens transcriptome highlights general challenges that remain for this technique. Furthermore, by applying riboswitch reporters in vivo, we identify new growth conditions and transposon mutations that affect cGAMP levels in G. sulfurreducens. This work reveals an extensive regulatory network and supports a second functional cGAMP synthase gene in G. sulfurreducens. The activity of the second synthase was validated using riboswitch-based fluorescent biosensors, and is the first known example of an active enzyme with a variant GGDDF motif.
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Bossé JT, Li Y, Leanse LG, Zhou L, Chaudhuri RR, Peters SE, Wang J, Maglennon GA, Holden MTG, Maskell DJ, Tucker AW, Wren BW, Rycroft AN, Langford PR. Rationally designed mariner vectors for functional genomic analysis of Actinobacillus pleuropneumoniae and other Pasteurellaceae species by transposon-directed insertion-site sequencing (TraDIS). ANIMAL DISEASES 2021; 1:29. [PMID: 34870287 PMCID: PMC8616859 DOI: 10.1186/s44149-021-00026-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Accepted: 09/14/2021] [Indexed: 11/26/2022] Open
Abstract
Comprehensive identification of conditionally essential genes requires efficient tools for generating high-density transposon libraries that, ideally, can be analysed using next-generation sequencing methods such as Transposon Directed Insertion-site Sequencing (TraDIS). The Himar1 (mariner) transposon is ideal for generating near-saturating mutant libraries, especially in AT-rich chromosomes, as the requirement for integration is a TA dinucleotide, and this transposon has been used for mutagenesis of a wide variety of bacteria. However, plasmids for mariner delivery do not necessarily work well in all bacteria. In particular, there are limited tools for functional genomic analysis of Pasteurellaceae species of major veterinary importance, such as swine and cattle pathogens, Actinobacillus pleuropneumoniae and Pasteurella multocida, respectively. Here, we developed plasmids, pTsodCPC9 and pTlacPC9 (differing only in the promoter driving expression of the transposase gene), that allow delivery of mariner into both these pathogens, but which should also be applicable to a wider range of bacteria. Using the pTlacPC9 vector, we have generated, for the first time, saturating mariner mutant libraries in both A. pleuropneumoniae and P. multocida that showed a near random distribution of insertions around the respective chromosomes as detected by TraDIS. A preliminary screen of 5000 mutants each identified 8 and 14 genes, respectively, that are required for growth under anaerobic conditions. Future high-throughput screening of the generated libraries will facilitate identification of mutants required for growth under different conditions, including in vivo, highlighting key virulence factors and pathways that can be exploited for development of novel therapeutics and vaccines.
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Affiliation(s)
- Janine T Bossé
- Section of Paediatric Infectious Disease, Department of Infectious Disease, Imperial College London, St. Mary's Campus, London, UK
| | - Yanwen Li
- Section of Paediatric Infectious Disease, Department of Infectious Disease, Imperial College London, St. Mary's Campus, London, UK
| | - Leon G Leanse
- Section of Paediatric Infectious Disease, Department of Infectious Disease, Imperial College London, St. Mary's Campus, London, UK.,Present Address: Wellman Center for Photomedicine, Harvard Medical School, Boston, USA
| | - Liqing Zhou
- Section of Paediatric Infectious Disease, Department of Infectious Disease, Imperial College London, St. Mary's Campus, London, UK.,Present Address: The Applied Diagnostic Research and Evaluation Unit, St George's University of London, London, UK
| | - Roy R Chaudhuri
- Department of Veterinary Medicine, University of Cambridge, Cambridge, UK.,Present Address: Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, UK
| | - Sarah E Peters
- Department of Veterinary Medicine, University of Cambridge, Cambridge, UK
| | - Jinhong Wang
- Department of Veterinary Medicine, University of Cambridge, Cambridge, UK
| | - Gareth A Maglennon
- Department of Pathology and Pathogen Biology, The Royal Veterinary College, Hatfield, UK
| | - Matthew T G Holden
- The Wellcome Trust Sanger Institute, Cambridge, UK.,Present Address: School of Medicine, University of St Andrews, St Andrews, UK
| | - Duncan J Maskell
- Department of Veterinary Medicine, University of Cambridge, Cambridge, UK.,Present Address: The University of Melbourne, Parkville, Victoria Australia
| | - Alexander W Tucker
- Department of Veterinary Medicine, University of Cambridge, Cambridge, UK
| | - Brendan W Wren
- Faculty of Infectious & Tropical Diseases, London School of Hygiene & Tropical Medicine, London, UK
| | - Andrew N Rycroft
- Department of Pathology and Pathogen Biology, The Royal Veterinary College, Hatfield, UK
| | - Paul R Langford
- Section of Paediatric Infectious Disease, Department of Infectious Disease, Imperial College London, St. Mary's Campus, London, UK
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12
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Abstract
Azotobacter vinelandii is a nitrogen-fixing free-living soil microbe that has been studied for decades in relation to biological nitrogen fixation (BNF). It is highly amenable to genetic manipulation, helping to unravel the intricate importance of different proteins involved in the process of BNF, including the biosynthesis of cofactors that are essential to assembling the complex metal cofactors that catalyze the difficult reaction of nitrogen fixation. Additionally, A. vinelandii accomplishes this feat while growing as an obligate aerobe, differentiating it from many of the nitrogen-fixing bacteria that are associated with plant roots. The ability to function in the presence of oxygen makes A. vinelandii suitable for application in various potential biotechnological schemes. In this study, we employed transposon sequencing (Tn-seq) to measure the fitness defects associated with disruptions of various genes under nitrogen-fixing dependent growth, versus growth with extraneously provided urea as a nitrogen source. The results allowed us to probe the importance of more than 3,800 genes, revealing that many genes previously believed to be important, can be successfully disrupted without impacting cellular fitness. IMPORTANCE These results provide insights into the functional redundancy in A. vinelandii, while also providing a direct measure of fitness for specific genes associated with the process of BNF. These results will serve as a valuable reference tool in future studies to uncover the mechanisms that govern this process.
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13
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Bertling K, Banerjee A, Saffarini D. Aerobic Respiration and Its Regulation in the Metal Reducer Shewanella oneidensis. Front Microbiol 2021; 12:723835. [PMID: 34566926 PMCID: PMC8458880 DOI: 10.3389/fmicb.2021.723835] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Accepted: 07/26/2021] [Indexed: 11/23/2022] Open
Abstract
Shewanella oneidensis MR-1 is a facultative anaerobe known for its ability to reduce metal oxides. Anaerobic respiration, especially metal reduction, has been the subject of extensive research. In contrast, S. oneidensis aerobic respiration has received less attention. S. oneidensis expresses cbb3- and aa3-type cytochrome c oxidases and a bd-type quinol oxidase. The aa3-type oxidase, which in other bacteria is the major oxygen reductase under oxygen replete conditions, does not appear to contribute to aerobic respiration and growth in S. oneidensis. Our results indicated that although the aa3-type oxidase does not play a role in aerobic growth on lactate, the preferred carbon source for S. oneidensis, it is involved in growth on pyruvate or acetate. These results highlight the importance of testing multiple carbon and energy sources when attempting to identify enzyme activities and mutant phenotypes. Several regulatory proteins contribute to the regulation of aerobic growth in S. oneidensis including CRP and ArcA. The 3',5'-cAMP phosphodiesterase (CpdA) appears to play a more significant role in aerobic growth than either CRP or ArcA, yet the deficiency does not appear to be the result of reduced oxidase genes expression. Interestingly, the ∆cpdA mutant was more deficient in aerobic respiration with several carbon sources tested compared to ∆crp, which was moderately deficient only in the presence of lactate. To identify the reason for ∆cpdA aerobic growth deficiency, we isolated a suppressor mutant with transposon insertion in SO_3550. Inactivation of this gene, which encodes an anti-sigma factor, restored aerobic growth in the cpdA mutant to wild-type levels. Inactivation of SO_3550 in wild-type cells, however, did not affect aerobic growth. The S. oneidensis genome encodes two additional CRP-like proteins that we designated CrpB and CrpC. Mutants that lack crpB and crpC were deficient in aerobic growth, but this deficiency was not due to the loss of oxidase gene expression.
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Affiliation(s)
- Kristen Bertling
- Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI, United States
| | - Areen Banerjee
- Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI, United States
| | - Daad Saffarini
- Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI, United States
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14
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Evidence for Horizontal and Vertical Transmission of Mtr-Mediated Extracellular Electron Transfer among the Bacteria. mBio 2021; 13:e0290421. [PMID: 35100867 PMCID: PMC8805035 DOI: 10.1128/mbio.02904-21] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Some bacteria and archaea have evolved the means to use extracellular electron donors and acceptors for energy metabolism, a phenomenon broadly known as extracellular electron transfer (EET). One such EET mechanism is the transmembrane electron conduit MtrCAB, which has been shown to transfer electrons derived from metabolic substrates to electron acceptors, like Fe(III) and Mn(IV) oxides, outside the cell. Although most studies of MtrCAB-mediated EET have been conducted in Shewanella oneidensis MR-1, recent investigations in Vibrio and Aeromonas species have revealed that the electron-donating proteins that support MtrCAB in Shewanella are not as representative as previously thought. This begs the question of how widespread the capacity for MtrCAB-mediated EET is, the changes it has accrued in different lineages, and where these lineages persist today. Here, we employed a phylogenetic and comparative genomics approach to identify the MtrCAB system across all domains of life. We found mtrCAB in the genomes of numerous diverse Bacteria from a wide range of environments, and the patterns therein strongly suggest that mtrCAB was distributed through both horizontal and subsequent vertical transmission, and with some cases indicating downstream modular diversification of both its core and accessory components. Our data point to an emerging evolutionary story about metal-oxidizing and -reducing metabolism, demonstrates that this capacity for EET has broad relevance to a diversity of taxa and the biogeochemical cycles they drive, and lays the foundation for further studies to shed light on how this mechanism may have coevolved with Earth's redox landscape. IMPORTANCE While many metabolisms make use of soluble, cell-permeable substrates like oxygen or hydrogen, there are other substrates, like iron or manganese, that cannot be brought into the cell. Some bacteria and archaea have evolved the means to directly "plug in" to such environmental electron reservoirs in a process known as extracellular electron transfer (EET), making them powerful agents of biogeochemical change and promising vehicles for bioremediation and alternative energy. Yet the diversity, distribution, and evolution of EET mechanisms are poorly constrained. Here, we present findings showing that the genes encoding one such EET system (mtrCAB) are present in a broad diversity of bacteria found in a wide range of environments, emphasizing the ubiquity and potential impact of EET in our biosphere. Our results suggest that these genes have been disseminated largely through horizontal transfer, and the changes they have accrued in these lineages potentially reflect adaptations to changing environments.
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15
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Kreienbaum M, Dörrich AK, Brandt D, Schmid NE, Leonhard T, Hager F, Brenzinger S, Hahn J, Glatter T, Ruwe M, Briegel A, Kalinowski J, Thormann KM. Isolation and Characterization of Shewanella Phage Thanatos Infecting and Lysing Shewanella oneidensis and Promoting Nascent Biofilm Formation. Front Microbiol 2020; 11:573260. [PMID: 33072035 PMCID: PMC7530303 DOI: 10.3389/fmicb.2020.573260] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Accepted: 08/27/2020] [Indexed: 01/21/2023] Open
Abstract
Species of the genus Shewanella are widespread in nature in various habitats, however, little is known about phages affecting Shewanella sp. Here, we report the isolation of phages from diverse freshwater environments that infect and lyse strains of Shewanella oneidensis and other Shewanella sp. Sequence analysis and microscopic imaging strongly indicate that these phages form a so far unclassified genus, now named Shewanella phage Thanatos, which can be positioned within the subfamily of Tevenvirinae (Duplodnaviria; Heunggongvirae; Uroviricota; Caudoviricetes; Caudovirales; Myoviridae; Tevenvirinae). We characterized one member of this group in more detail using S. oneidensis MR-1 as a host. Shewanella phage Thanatos-1 possesses a prolate icosahedral capsule of about 110 nm in height and 70 nm in width and a tail of about 95 nm in length. The dsDNA genome exhibits a GC content of about 34.5%, has a size of 160.6 kbp and encodes about 206 proteins (92 with an annotated putative function) and two tRNAs. Out of those 206, MS analyses identified about 155 phage proteins in PEG-precipitated samples of infected cells. Phage attachment likely requires the outer lipopolysaccharide of S. oneidensis, narrowing the phage's host range. Under the applied conditions, about 20 novel phage particles per cell were produced after a latent period of approximately 40 min, which are stable at a pH range from 4 to 12 and resist temperatures up to 55°C for at least 24 h. Addition of Thanatos to S. oneidensis results in partial dissolution of established biofilms, however, early exposure of planktonic cells to Thanatos significantly enhances biofilm formation. Taken together, we identified a novel genus of Myophages affecting S. oneidensis communities in different ways.
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Affiliation(s)
- Maximilian Kreienbaum
- Department of Microbiology and Molecular Biology, Justus Liebig University Giessen, Giessen, Germany
| | - Anja K Dörrich
- Department of Microbiology and Molecular Biology, Justus Liebig University Giessen, Giessen, Germany
| | - David Brandt
- Center for Biotechnology, Bielefeld University, Bielefeld, Germany
| | - Nicole E Schmid
- Department of Microbiology and Molecular Biology, Justus Liebig University Giessen, Giessen, Germany
| | - Tabea Leonhard
- Department of Microbiology and Molecular Biology, Justus Liebig University Giessen, Giessen, Germany
| | - Fabian Hager
- Department of Microbiology and Molecular Biology, Justus Liebig University Giessen, Giessen, Germany
| | - Susanne Brenzinger
- Department of Molecular Biotechnology, Institute of Biology, Leiden University, Leiden, Netherlands
| | - Julia Hahn
- Center for Biotechnology, Bielefeld University, Bielefeld, Germany
| | - Timo Glatter
- Facility for Mass Spectrometry and Proteomics, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Matthias Ruwe
- Center for Biotechnology, Bielefeld University, Bielefeld, Germany
| | - Ariane Briegel
- Department of Molecular Biotechnology, Institute of Biology, Leiden University, Leiden, Netherlands
| | - Jörn Kalinowski
- Center for Biotechnology, Bielefeld University, Bielefeld, Germany
| | - Kai M Thormann
- Department of Microbiology and Molecular Biology, Justus Liebig University Giessen, Giessen, Germany
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16
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Gene expression abundance dictated exopolysaccharide modification in Rhizobium radiobacter SZ4S7S14 as the cell's response to salt stress. Int J Biol Macromol 2020; 164:4339-4347. [PMID: 32931833 DOI: 10.1016/j.ijbiomac.2020.09.038] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Revised: 08/25/2020] [Accepted: 09/07/2020] [Indexed: 12/24/2022]
Abstract
A molecular and metabolic behaviour of EPS-producing and salt-tolerant bacterium Rhizobium radiobacter SZ4S7S14 along with its practical application in salt-stress was investigated. The research target was identification and expression profiles of a large EPS biosynthesis gene cluster, possible structural modification of EPS under salt-stress effect and analysis of the gene(s) relative expression and structural modification correlation. As expected, transposons insertions were identified within or near the coding regions of exoK and exoM, previously known large gene cluster that is required for EPS I synthesis. Different expression levels of exoK and exoM in different salt-stress models resulted in structural modification of EPS, which was seen basically in monomers molar ratio. As a result of downregulation of the genes the strain produced EPS samples with monomers ratio: (1) Glu:Man:Gal:Xyl:Ara:Rha:Rib = 31.21:3.02:2.77:1:0.91:0.64:0.41 (in 0.25% NaCl); (2) Glu:Man:Gal:Xyl:Ara:Rha:Rib = 7.65:1:0.69:0.22:0.2:0.16:0.1 (in 0.5% NaCl); (3) Glu:Man:Gal:Ara:Xyl:Rha:Rib = 9.39:1.89:1:0.58:0.52:0.46:0.26 (in 1% NaCl); and (4) Glu:Man:Ara:Xyl:Rib:Gal = 7.9:2:2:1.58:1.1:1 (in 2.0% NaCl), whereas in control (without NaCl): Glc:Man:Gal:Xyl:Ara:Rha:Rib = 11.66:1:0.90:0.37:0.37:0.15:0.14. It was found that, salt-stress not only leads to downregulation of a large EPS biosynthesis gene cluster, including exoK and exoM genes, but also impacting on their relative expression degree, re-groups of the monomers within the EPS matrix and dictates molar ratio of the monosaccharides in the final metabolite.
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17
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Yuan X, Zeng Q, Xu J, Severin GB, Zhou X, Waters CM, Sundin GW, Ibekwe AM, Liu F, Yang CH. Tricarboxylic Acid (TCA) Cycle Enzymes and Intermediates Modulate Intracellular Cyclic di-GMP Levels and the Production of Plant Cell Wall-Degrading Enzymes in Soft Rot Pathogen Dickeya dadantii. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2020; 33:296-307. [PMID: 31851880 PMCID: PMC9354473 DOI: 10.1094/mpmi-07-19-0203-r] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Dickeya dadantii is a plant-pathogenic bacterium that causes soft-rot in a wide range of plants. Although we have previously demonstrated that cyclic bis-(3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP), a bacterial secondary messenger, plays a central role in virulence regulation in D. dadantii, the upstream signals that modulate c-di-GMP remain enigmatic. Using a genome-wide transposon mutagenesis approach of a Δhfq mutant strain that has high c-di-GMP and reduced motility, we uncovered transposon mutants that recovered the c-di-GMP-mediated repression on swimming motility. A number of these mutants harbored transposon insertions in genes encoding tricarboxylic acid (TCA) cycle enzymes. Two of these TCA transposon mutants were studied further by generating chromosomal deletions of the fumA gene (encoding fumarase) and the sdhCDAB operon (encoding succinate dehydrogenase). Disruption of the TCA cycle in these deletion mutants resulted in reduced intracellular c-di-GMP and enhanced production of pectate lyases (Pels), a major plant cell wall-degrading enzyme (PCWDE) known to be transcriptionally repressed by c-di-GMP. Consistent with this result, addition of TCA cycle intermediates such as citrate also resulted in increased c-di-GMP levels and decreased production of Pels. Additionally, we found that a diguanylate cyclase GcpA was solely responsible for the observed citrate-mediated modulation of c-di-GMP. Finally, we demonstrated that addition of citrate induced not only an overproduction of GcpA protein but also a concomitant repression of the c-di-GMP-degrading phosphodiesterase EGcpB which, together, resulted in an increase in the intracellular concentration of c-di-GMP. In summary, our report demonstrates that bacterial respiration and respiration metabolites serve as signals for the regulation of c-di-GMP signaling.
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Affiliation(s)
- Xiaochen Yuan
- Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, Jiangsu Key Laboratory for Food Quality and Safety-State Key Laboratory Cultivation Base of Ministry of Science and Technology, Nanjing, 210014, China
- Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, U.S.A
| | - Quan Zeng
- Department of Plant Pathology and Ecology, The Connecticut Agricultural Experiment Station, New Haven, CT 06511, U.S.A
| | - Jingsheng Xu
- Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
| | - Geoffrey B. Severin
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, U.S.A
| | - Xiang Zhou
- School of Forestry and Biotechnology, Zhejiang Agricultural and Forestry University, Hangzhou, 311300, China
| | | | - George W. Sundin
- Department of Plant, Soil, and Microbial Sciences, Michigan State University
| | - Abasiofiok M. Ibekwe
- Agricultural Research Service-US Salinity Laboratory, United States Department of Agriculture, Riverside, CA 92507, U.S.A
| | - Fengquan Liu
- Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, Jiangsu Key Laboratory for Food Quality and Safety-State Key Laboratory Cultivation Base of Ministry of Science and Technology, Nanjing, 210014, China
| | - Ching-Hong Yang
- Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, U.S.A
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18
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Regulation and Maturation of the Shewanella oneidensis Sulfite Reductase SirA. Sci Rep 2020; 10:953. [PMID: 31969587 PMCID: PMC6976685 DOI: 10.1038/s41598-020-57587-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Accepted: 12/27/2019] [Indexed: 01/12/2023] Open
Abstract
Shewanella oneidensis, a metal reducer and facultative anaerobe, expresses a large number of c-type cytochromes, many of which function as anaerobic reductases. All of these proteins contain the typical heme-binding motif CXXCH and require the Ccm proteins for maturation. Two c-type cytochrome reductases also possess atypical heme-binding sites, the NrfA nitrite reductase (CXXCK) and the SirA sulfite reductase (CX12NKGCH). S. oneidensis MR-1 encodes two cytochrome c synthetases (CcmF and SirE) and two apocytochrome c chaperones (CcmI and SirG). SirE located in the sir gene cluster is required for the maturation of SirA, but not NrfA. Here we show that maturation of SirA requires the combined function of the two apocytochrome c chaperones CcmI and SirG. Loss of either protein resulted in decreased sulfite reductase. Furthermore, SirA was not detected in a mutant that lacked both chaperones, perhaps due to misfolding or instability. These results suggest that CcmI interacts with SirEFG during SirA maturation, and with CcmF during maturation of NrfA. Additionally, we show that CRP regulates expression of sirA via the newly identified transcriptional regulatory protein, SirR.
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19
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A Dual-Species Biofilm with Emergent Mechanical and Protective Properties. J Bacteriol 2019; 201:JB.00670-18. [PMID: 30833350 DOI: 10.1128/jb.00670-18] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Accepted: 02/23/2019] [Indexed: 12/14/2022] Open
Abstract
Many microbes coexist within biofilms, or multispecies communities of cells encased in an extracellular matrix. However, little is known about the microbe-microbe interactions relevant for creating these structures. In this study, we explored a striking dual-species biofilm between Bacillus subtilis and Pantoea agglomerans that exhibited characteristics that were not predictable from previous work examining monoculture biofilms. Coculture wrinkle formation required a P. agglomerans exopolysaccharide as well as the B. subtilis amyloid-like protein TasA. Unexpectedly, other B. subtilis matrix components essential for monoculture biofilm formation were not necessary for coculture wrinkling (e.g., the exopolysaccharide EPS, the hydrophobin BslA, and cell chaining). In addition, B. subtilis cell chaining prevented coculture wrinkling, even though chaining was previously associated with more robust monoculture biofilms. We also observed that increasing the relative proportion of P. agglomerans (which forms completely featureless monoculture colonies) increased coculture wrinkling. Using microscopy and rheology, we observed that these two bacteria assemble into an organized layered structure that reflects the physical properties of both monocultures. This partitioning into distinct regions negatively affected the survival of P. agglomerans while also serving as a protective mechanism in the presence of antibiotic stress. Taken together, these data indicate that studying cocultures is a productive avenue to identify novel mechanisms that drive the formation of structured microbial communities.IMPORTANCE In the environment, many microbes form biofilms. However, the interspecies interactions underlying bacterial coexistence within these biofilms remain understudied. Here, we mimic environmentally relevant biofilms by studying a dual-species biofilm formed between Bacillus subtilis and Pantoea agglomerans and subjecting the coculture to chemical and physical stressors that it may experience in the natural world. We determined that both bacteria contribute structural elements to the coculture, which is reflected in its overall viscoelastic behavior. Existence within the coculture can be either beneficial or detrimental depending on the context. Many of the features and determinants of the coculture biofilm appear distinct from those identified in monoculture biofilm studies, highlighting the importance of characterizing multispecies consortia to understand naturally occurring bacterial interactions.
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20
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Dai J, Liu Y, Liu S, Li S, Gao N, Wang J, Zhou J, Qiu D. Differential gene content and gene expression for bacterial evolution and speciation of Shewanella in terms of biosynthesis of heme and heme-requiring proteins. BMC Microbiol 2019; 19:173. [PMID: 31362704 PMCID: PMC6664582 DOI: 10.1186/s12866-019-1549-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Accepted: 07/19/2019] [Indexed: 01/31/2023] Open
Abstract
Background Most species of Shewanella harbor two ferrochelatase paralogues for the biosynthesis of c-type cytochromes, which are crucial for their respiratory versatility. In our previous study of the Shewanella loihica PV-4 strain, we found that the disruption of hemH1 but not hemH2 resulted in a significant accumulation of extracellular protoporphyrin IX (PPIX), but it is different in Shewanella oneidensis MR-1. Hence, the function and transcriptional regulation of two ferrochelatase genes, hemH1 and hemH2, are investigated in S. oneidensis MR-1. Result In the present study, deletion of either hemH1 or hemH2 in S. oneidensis MR-1 did not lead to overproduction of extracellular protoporphyrin IX (PPIX) as previously described in the hemH1 mutants of S. loihica PV-4. Moreover, supplement of exogenous hemins made it possible to generate the hemH1 and hemH2 double mutant in MR-1, but not in PV-4. Under aerobic condition, exogenous hemins were required for the growth of MR-1ΔhemH1ΔhemH2, which also overproduced extracellular PPIX. These results suggest that heme is essential for aerobic growth of Shewanella species and MR-1 could also uptake hemin for biosynthesis of essential cytochrome(s) and respiration. Besides, the exogenous hemin mediated CymA cytochrome maturation and the cellular KatB catalase activity. Both hemH paralogues were transcribed in wild-type MR-1, and the hemH2 transcription was remarkably up-regulated in MR-1ΔhemH1 mutant to compensate for the loss of hemH1. The periplasmic glutathione peroxidase gene pgpD, located in the same operon with hemH2, and a large gene cluster coding for iron, heme (hemin) uptake systems are absent in the PV-4 genome. Conclusion Our results indicate that the genetic divergence in gene content and gene expression between these Shewanella species, accounting for the phenotypic difference described here, might be due to their speciation and adaptation to the specific habitats (iron-rich deep-sea vent versus iron-poor freshwater) in which they evolved and the generated mutants could potentially be utilized for commercial production of PPIX. Electronic supplementary material The online version of this article (10.1186/s12866-019-1549-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Jingcheng Dai
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, Hubei Province, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yaqi Liu
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, Hubei Province, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Shuangyuan Liu
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, Hubei Province, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Shuyang Li
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, Hubei Province, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Na Gao
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, Hubei Province, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Jing Wang
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, Hubei Province, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Jizhong Zhou
- Institute for Environmental Genomics, and Department of Microbiology and Plant Biology, University of Oklahoma, Norman, OK, 73019, USA.,Earth Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94270, USA
| | - Dongru Qiu
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, Hubei Province, China. .,University of Chinese Academy of Sciences, Beijing, 100049, China.
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21
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Chellamuthu P, Naughton K, Pirbadian S, Silva KPT, Chavez MS, El-Naggar MY, Boedicker J. Biogenic Control of Manganese Doping in Zinc Sulfide Nanomaterial Using Shewanella oneidensis MR-1. Front Microbiol 2019; 10:938. [PMID: 31134005 PMCID: PMC6514046 DOI: 10.3389/fmicb.2019.00938] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Accepted: 04/12/2019] [Indexed: 12/03/2022] Open
Abstract
Bacteria naturally alter the redox state of many compounds and perform atom-by-atom nanomaterial synthesis to create many inorganic materials. Recent advancements in synthetic biology have spurred interest in using biological systems to manufacture nanomaterials, implementing biological strategies to specify the nanomaterial characteristics such as size, shape, and optical properties. Here, we combine the natural synthetic capabilities of microbes with engineered genetic control circuits toward biogenically synthesized semiconductor nanomaterials. Using an engineered strain of Shewanella oneindensis with inducible expression of the cytochrome complex MtrCAB, we control the reduction of manganese (IV) oxide. Cytochrome expression levels were regulated using an inducer molecule, which enabled precise modulation of dopant incorporation into manganese doped zinc sulfide nanoparticles (Mn:ZnS). Thereby, a synthetic gene circuit controlled the optical properties of biogenic quantum dots. These biogenically assembled nanomaterials have similar physical and optoelectronic properties to chemically synthesized particles. Our results demonstrate the promise of implementing synthetic gene circuits for tunable control of nanomaterials made by biological systems.
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Affiliation(s)
- Prithiviraj Chellamuthu
- Department of Physics and Astronomy, University of Southern California, Los Angeles, CA, United States
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, United States
| | - Kyle Naughton
- Department of Physics and Astronomy, University of Southern California, Los Angeles, CA, United States
| | - Sahand Pirbadian
- Department of Physics and Astronomy, University of Southern California, Los Angeles, CA, United States
| | - Kalinga Pavan T. Silva
- Department of Physics and Astronomy, University of Southern California, Los Angeles, CA, United States
| | - Marko S. Chavez
- Department of Physics and Astronomy, University of Southern California, Los Angeles, CA, United States
| | - Mohamed Y. El-Naggar
- Department of Physics and Astronomy, University of Southern California, Los Angeles, CA, United States
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, United States
- Department of Chemistry, University of Southern California, Los Angeles, CA, United States
| | - James Boedicker
- Department of Physics and Astronomy, University of Southern California, Los Angeles, CA, United States
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, United States
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22
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Conte E, Mende L, Grainge I, Colloms SD. A Mini-ISY100 Transposon Delivery System Effective in γ Proteobacteria. Front Microbiol 2019; 10:280. [PMID: 30873132 PMCID: PMC6400869 DOI: 10.3389/fmicb.2019.00280] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Accepted: 02/04/2019] [Indexed: 11/17/2022] Open
Abstract
Transposons are invaluable biological tools for the genetic manipulation of microorganisms. ISY100 from Synechocystis sp. PCC6803 is a member of the Tc1/mariner/IS630 superfamily, and is characterized by high transposition efficiency and a strong preference for TA target sequences. In this paper, we describe the design and application of a mini-ISY100 suicide vector for the in vivo creation of stable random transposon insertion libraries. The system was successfully applied in seven species belonging to four different orders of γ proteobacteria. In all cases, delivery using conjugation consistently showed the highest transposition efficiency compared to chemical transformation or electroporation. We determined the frequency of transposon insertions in all the species and proved the utility of the system by identifying genes involved in colony coloration in Shewanella oneidensis. The ease and the efficiency of the protocol developed here allow the creation of complete knock-out libraries in an extensive range of host microorganisms in less than a week with no requirement for preparatory modification.
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Affiliation(s)
- Emanuele Conte
- Institute of Molecular Cell and Systems Biology, University of Glasgow, Glasgow, United Kingdom
| | - Linda Mende
- School of Environmental and Life Sciences, University of Newcastle, Newcastle, NSW, Australia
| | - Ian Grainge
- School of Environmental and Life Sciences, University of Newcastle, Newcastle, NSW, Australia
| | - Sean D Colloms
- Institute of Molecular Cell and Systems Biology, University of Glasgow, Glasgow, United Kingdom
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23
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Brenzinger S, Pecina A, Mrusek D, Mann P, Völse K, Wimmi S, Ruppert U, Becker A, Ringgaard S, Bange G, Thormann KM. ZomB is essential for flagellar motor reversals in Shewanella putrefaciens and Vibrio parahaemolyticus. Mol Microbiol 2018; 109:694-709. [PMID: 29995998 DOI: 10.1111/mmi.14070] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/10/2018] [Indexed: 01/05/2023]
Abstract
The ability of most bacterial flagellar motors to reverse the direction of rotation is crucial for efficient chemotaxis. In Escherichia coli, motor reversals are mediated by binding of phosphorylated chemotaxis protein CheY to components of the flagellar rotor, FliM and FliN, which induces a conformational switch of the flagellar C-ring. Here, we show that for Shewanella putrefaciens, Vibrio parahaemolyticus and likely a number of other species an additional transmembrane protein, ZomB, is critically required for motor reversals as mutants lacking ZomB exclusively exhibit straightforward swimming also upon full phosphorylation or overproduction of CheY. ZomB is recruited to the cell poles by and is destabilized in the absence of the polar landmark protein HubP. ZomB also co-localizes to and may thus interact with the flagellar motor. The ΔzomB phenotype was suppressed by mutations in the very C-terminal region of FliM. We propose that the flagellar motors of Shewanella, Vibrio and numerous other species harboring orthologs to ZomB are locked in counterclockwise rotation and may require interaction with ZomB to enable the conformational switch required for motor reversals. Regulation of ZomB activity or abundance may provide these species with an additional means to modulate chemotaxis efficiency.
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Affiliation(s)
- Susanne Brenzinger
- Justus-Liebig Universität, Department of Microbiology and Molecular Biology, 35392, Giessen, Germany
| | - Anna Pecina
- Justus-Liebig Universität, Department of Microbiology and Molecular Biology, 35392, Giessen, Germany
| | - Devid Mrusek
- LOEWE Center for Synthetic Microbiology (Synmikro) & Department of Chemistry, Philipps-Universität Marburg, 35043, Marburg, Germany
| | - Petra Mann
- Department of Ecophysiology, Max-Planck-Institut für terrestrische Mikrobiologie, 35043, Marburg, Germany
| | - Kerstin Völse
- Justus-Liebig Universität, Department of Microbiology and Molecular Biology, 35392, Giessen, Germany
| | - Stephan Wimmi
- Department of Ecophysiology, Max-Planck-Institut für terrestrische Mikrobiologie, 35043, Marburg, Germany
| | - Ulrike Ruppert
- Justus-Liebig Universität, Department of Microbiology and Molecular Biology, 35392, Giessen, Germany
| | - Anke Becker
- LOEWE Center for Synthetic Microbiology (Synmikro) & Department of Biology, Philipps-Universität Marburg, 35043, Marburg, Germany
| | - Simon Ringgaard
- Department of Ecophysiology, Max-Planck-Institut für terrestrische Mikrobiologie, 35043, Marburg, Germany
| | - Gert Bange
- LOEWE Center for Synthetic Microbiology (Synmikro) & Department of Chemistry, Philipps-Universität Marburg, 35043, Marburg, Germany
| | - Kai M Thormann
- Justus-Liebig Universität, Department of Microbiology and Molecular Biology, 35392, Giessen, Germany
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24
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Bennett BD, Redford KE, Gralnick JA. Survival of Anaerobic Fe 2+ Stress Requires the ClpXP Protease. J Bacteriol 2018; 200:e00671-17. [PMID: 29378887 PMCID: PMC5869471 DOI: 10.1128/jb.00671-17] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Accepted: 01/23/2018] [Indexed: 11/20/2022] Open
Abstract
Shewanella oneidensis strain MR-1 is a versatile bacterium capable of respiring extracellular, insoluble ferric oxide minerals under anaerobic conditions. The respiration of iron minerals results in the production of soluble ferrous ions, which at high concentrations are toxic to living organisms. It is not fully understood how Fe2+ is toxic to cells anaerobically, nor is it fully understood how S. oneidensis is able to resist high levels of Fe2+ Here we describe the results of a transposon mutant screen and subsequent deletion of the genes clpX and clpP in S. oneidensis, which demonstrate that the protease ClpXP is required for anaerobic Fe2+ resistance. Many cellular processes are known to be regulated by ClpXP, including entry into stationary phase, envelope stress response, and turnover of stalled ribosomes. However, none of these processes appears to be responsible for mediating anaerobic Fe2+ resistance in S. oneidensis Protein trapping studies were performed to identify ClpXP targets in S. oneidensis under Fe2+ stress, implicating a wide variety of protein targets. Escherichia coli strains lacking clpX or clpP also display increased sensitivity to Fe2+ anaerobically, indicating Fe2+ resistance may be a conserved role for the ClpXP protease system. Hypotheses regarding the potential role(s) of ClpXP during periods of high Fe2+ are discussed. We speculate that metal-containing proteins are misfolded under conditions of high Fe2+ and that the ClpXP protease system is necessary for their turnover.IMPORTANCE Prior to the evolution of cyanobacteria and oxygenic photosynthesis, life arose and flourished in iron-rich oceans. Today, aqueous iron-rich environments are less common, constrained to low-pH conditions and anaerobic systems such as stratified lakes and seas, digestive tracts, subsurface environments, and sediments. The latter two ecosystems often favor dissimilatory metal reduction, a process that produces soluble Fe2+ from iron oxide minerals. Dissimilatory metal-reducing bacteria must therefore have mechanisms to tolerate anaerobic Fe2+ stress, and studying resistance in these organisms may help elucidate the basis of toxicity. Shewanella oneidensis is a model dissimilatory metal-reducing bacterium isolated from metal-rich sediments. Here we demonstrate a role for ClpXP, a protease system widely conserved in bacteria, in anaerobic Fe2+ resistance in both S. oneidensis and Escherichia coli.
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Affiliation(s)
- Brittany D Bennett
- BioTechnology Institute and Department of Plant and Microbial Biology, University of Minnesota-Twin Cities, St. Paul, Minnesota, USA
| | - Kaitlyn E Redford
- BioTechnology Institute and Department of Plant and Microbial Biology, University of Minnesota-Twin Cities, St. Paul, Minnesota, USA
| | - Jeffrey A Gralnick
- BioTechnology Institute and Department of Plant and Microbial Biology, University of Minnesota-Twin Cities, St. Paul, Minnesota, USA
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25
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Gao N, Xia M, Dai J, Yu D, An W, Li S, Liu S, He P, Zhang L, Wu Z, Bi X, Chen S, Haft DH, Qiu D. Both widespread PEP-CTERM proteins and exopolysaccharides are required for floc formation of Zoogloea resiniphila and other activated sludge bacteria. Environ Microbiol 2018; 20:1677-1692. [PMID: 29473278 DOI: 10.1111/1462-2920.14080] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Revised: 02/12/2018] [Accepted: 02/19/2018] [Indexed: 12/28/2022]
Abstract
Bacterial floc formation plays a central role in the activated sludge (AS) process, which has been widely utilized for sewage and wastewater treatment. The formation of AS flocs has long been known to require exopolysaccharide biosynthesis. This study demonstrates an additional requirement for a PEP-CTERM protein in Zoogloea resiniphila, a dominant AS bacterium harboring a large exopolysaccharide biosynthesis gene cluster. Two members of a wide-spread family of high copy number-per-genome PEP-CTERM genes, transcriptionally regulated by the RpoN sigma factor and accessory PrsK-PrsR two-component system and at least one of these, pepA, must be expressed for Zoogloea to build the floc structures that allow gravitational sludge settling and recycling. Without PrsK or PrsR, Zoogloea cells were planktonic rather than flocculated and secreted exopolysaccharides were released into the growth broth in soluble form. Overexpression of PepA could circumvent the requirement of rpoN, prsK and prsR for the floc-forming phenotype by fixing the exopolysaccharides to bacterial cells. However, overexpression of PepA, which underwent post-translational modifications, could not rescue the long-rod morphology of the rpoN mutant. Consistently, PEP-CTERM genes and exopolysaccharide biosynthesis gene cluster are present in the genome of the floc-forming Nitrospira comammox and Mitsuaria strain as well as many other AS bacteria.
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Affiliation(s)
- Na Gao
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Ming Xia
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jingcheng Dai
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Dianzhen Yu
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Weixing An
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Shuyang Li
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Shuangyuan Liu
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Penghui He
- College of Life Sciences, Hubei University, Wuhan 430070, China
| | - Liping Zhang
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Zhenbin Wu
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Xuezhi Bi
- Agency for Science, Technology and Research, Bioprocessing Technology Institute, Singapore 138668, Singapore
| | - Shouwen Chen
- College of Life Sciences, Hubei University, Wuhan 430070, China
| | - Daniel H Haft
- National Institutes of Health (NIH), Bethesda, MD 20892, USA
| | - Dongru Qiu
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
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26
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Inactivation of the Major Hemolysin Gene Influences Expression of the Nonribosomal Peptide Synthetase Gene swrA in the Insect Pathogen Serratia sp. Strain SCBI. J Bacteriol 2017; 199:JB.00333-17. [PMID: 28784817 DOI: 10.1128/jb.00333-17] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Accepted: 08/03/2017] [Indexed: 11/20/2022] Open
Abstract
Hemolysins are important virulence factors for many bacterial pathogens, including Serratia marcescens The role of the major hemolysin gene in the insect pathogen Serratia sp. strain SCBI was investigated using both forward and reverse-genetics approaches. Introduction of the major hemolysin gene into Escherichia coli resulted in a gain of both virulence and hemolytic activity. Inactivation of this hemolysin in Serratia sp. SCBI resulted in a loss of hemolysis but did not attenuate insecticidal activity. Unexpectedly, inactivation of the hemolysin gene in Serratia sp. SCBI resulted in significantly increased motility and increased antimicrobial activity. Reverse transcription-quantitative PCR (qRT-PCR) analysis of mutants with a disrupted hemolysin gene showed a dramatic increase in mRNA levels of a nonribosomal peptide synthetase gene, swrA, which produces the surfactant serrawettin W2. Mutation of the swrA gene in Serratia sp. SCBI resulted in highly varied antibiotic activity, motility, virulence, and hemolysis phenotypes that were dependent on the site of disruption within this 17.75-kb gene. When introduced into E. coli, swrA increases rates of motility and confers antimicrobial activity. While it is unclear how inactivation of the major hemolysin gene influences the expression of swrA, these results suggest that swrA plays an important role in motility and antimicrobial activity in Serratia sp. SCBI.IMPORTANCE The opportunistic Gram-negative bacteria of the genus Serratia are widespread in the environment and can cause human illness. A comparative genomics analysis between Serratia marcescens and a new Serratia species from South Africa, termed Serratia sp. strain SCBI, shows that these two organisms are closely related but differ in pathogenesis. S. marcescens kills Caenorhabditis nematodes, while Serratia sp. SCBI is not harmful and forms a beneficial association with them. This distinction presented the opportunity to investigate potential differences in regulation of common virulence mechanisms between these two species. With the emergence of antibiotic-resistant microorganisms, there is a widespread need to understand the regulation of pathogenesis. The significance of this study is the presentation of evidence for cross-pathway regulation of virulence factors and how the elimination of one mechanism may be compensated for by the upregulation of others.
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27
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Anzai IA, Shaket L, Adesina O, Baym M, Barstow B. Rapid curation of gene disruption collections using Knockout Sudoku. Nat Protoc 2017; 12:2110-2137. [DOI: 10.1038/nprot.2017.073] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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28
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Genome Scale Mutational Analysis of Geobacter sulfurreducens Reveals Distinct Molecular Mechanisms for Respiration and Sensing of Poised Electrodes versus Fe(III) Oxides. J Bacteriol 2017; 199:JB.00340-17. [PMID: 28674067 PMCID: PMC5585712 DOI: 10.1128/jb.00340-17] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Accepted: 06/23/2017] [Indexed: 12/11/2022] Open
Abstract
Geobacter sulfurreducens generates electrical current by coupling intracellular oxidation of organic acids to the reduction of proteins on the cell surface that are able to interface with electrodes. This ability is attributed to the bacterium's capacity to respire other extracellular electron acceptors that require contact, such as insoluble metal oxides. To directly investigate the genetic basis of electrode-based respiration, we constructed Geobacter sulfurreducens transposon-insertion sequencing (Tn-Seq) libraries for growth, with soluble fumarate or an electrode as the electron acceptor. Libraries with >33,000 unique insertions and an average of 9 insertions/kb allowed an assessment of each gene's fitness in a single experiment. Mutations in 1,214 different genomic features impaired growth with fumarate, and the significance of 270 genes unresolved by annotation due to the presence of one or more functional homologs was determined. Tn-Seq analysis of −0.1 V versus standard hydrogen electrode (SHE) electrode-grown cells identified mutations in a subset of genes encoding cytochromes, processing systems for proline-rich proteins, sensory networks, extracellular structures, polysaccharides, and metabolic enzymes that caused at least a 50% reduction in apparent growth rate. Scarless deletion mutants of select genes identified via Tn-Seq revealed a new putative porin-cytochrome conduit complex (extABCD) crucial for growth with electrodes, which was not required for Fe(III) oxide reduction. In addition, four mutants lacking components of a putative methyl-accepting chemotaxis–cyclic dinucleotide sensing network (esnABCD) were defective in electrode colonization but grew normally with Fe(III) oxides. These results suggest that G. sulfurreducens possesses distinct mechanisms for recognition, colonization, and reduction of electrodes compared to Fe(III) oxides. IMPORTANCE Since metal oxide electron acceptors are insoluble, one hypothesis is that cells sense and reduce metals using the same molecular mechanisms used to form biofilms on electrodes and produce electricity. However, by simultaneously comparing thousands of Geobacter sulfurreducens transposon mutants undergoing electrode-dependent respiration, we discovered new cytochromes and chemosensory proteins supporting growth with electrodes that are not required for metal respiration. This supports an emerging model where G. sulfurreducens recognizes surfaces and forms conductive biofilms using mechanisms distinct from those used for growth with metal oxides. These findings provide a possible explanation for studies that correlate electricity generation with syntrophic interspecies electron transfer by Geobacter and reveal many previously unrecognized targets for engineering this useful capability in other organisms.
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RpoN (σ 54) Is Required for Floc Formation but Not for Extracellular Polysaccharide Biosynthesis in a Floc-Forming Aquincola tertiaricarbonis Strain. Appl Environ Microbiol 2017; 83:AEM.00709-17. [PMID: 28500044 DOI: 10.1128/aem.00709-17] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2017] [Accepted: 05/08/2017] [Indexed: 11/20/2022] Open
Abstract
Some bacteria are capable of forming flocs, in which bacterial cells become self-flocculated by secreted extracellular polysaccharides and other biopolymers. The floc-forming bacteria play a central role in activated sludge, which has been widely utilized for the treatment of municipal sewage and industrial wastewater. Here, we use a floc-forming bacterium, Aquincolatertiaricarbonis RN12, as a model to explore the biosynthesis of extracellular polysaccharides and the regulation of floc formation. A large gene cluster for exopolysaccharide biosynthesis and a gene encoding the alternative sigma factor RpoN1, one of the four paralogues, have been identified in floc formation-deficient mutants generated by transposon mutagenesis, and the gene functions have been further confirmed by genetic complementation analyses. Interestingly, the biosynthesis of exopolysaccharides remained in the rpoN1-disrupted flocculation-defective mutants, but most of the exopolysaccharides were secreted and released rather than bound to the cells. Furthermore, the expression of exopolysaccharide biosynthesis genes seemed not to be regulated by RpoN1. Taken together, our results indicate that RpoN1 may play a role in regulating the expression of a certain gene(s) involved in the self-flocculation of bacterial cells but not in the biosynthesis and secretion of exopolysaccharides required for floc formation.IMPORTANCE Floc formation confers bacterial resistance to predation of protozoa and plays a central role in the widely used activated sludge process. In this study, we not only identified a large gene cluster for biosynthesis of extracellular polysaccharides but also identified four rpoN paralogues, one of which (rpoN1) is required for floc formation in A. tertiaricarbonis RN12. In addition, this RpoN sigma factor regulates the transcription of genes involved in biofilm formation and swarming motility, as previously shown in other bacteria. However, this RpoN paralogue is not required for the biosynthesis of exopolysaccharides, which are released and dissolved into culture broth by the rpoN1 mutant rather than remaining tightly bound to cells, as observed during the flocculation of the wild-type strain. These results indicate that floc formation is a regulated complex process, and other yet-to-be identified RpoN1-dependent factors are involved in self-flocculation of bacterial cells via exopolysaccharides and/or other biopolymers.
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Rapid construction of a whole-genome transposon insertion collection for Shewanella oneidensis by Knockout Sudoku. Nat Commun 2016; 7:13270. [PMID: 27830751 PMCID: PMC5109470 DOI: 10.1038/ncomms13270] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Accepted: 09/14/2016] [Indexed: 02/07/2023] Open
Abstract
Whole-genome knockout collections are invaluable for connecting gene sequence to function, yet traditionally, their construction has required an extraordinary technical effort. Here we report a method for the construction and purification of a curated whole-genome collection of single-gene transposon disruption mutants termed Knockout Sudoku. Using simple combinatorial pooling, a highly oversampled collection of mutants is condensed into a next-generation sequencing library in a single day, a 30- to 100-fold improvement over prior methods. The identities of the mutants in the collection are then solved by a probabilistic algorithm that uses internal self-consistency within the sequencing data set, followed by rapid algorithmically guided condensation to a minimal representative set of mutants, validation, and curation. Starting from a progenitor collection of 39,918 mutants, we compile a quality-controlled knockout collection of the electroactive microbe Shewanella oneidensis MR-1 containing representatives for 3,667 genes that is functionally validated by high-throughput kinetic measurements of quinone reduction. Knockout collections provide a valuable tool to explore gene function, yet are expensive and technically challenging to produce at a genome-wide scale. Here Baym et al. devise a cost-effective transposon-based method to quickly develop a knockout collection for the electroactive microbe Shewanella oneidensis.
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31
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Mitra S, Mukherjee A, Wiley-Kalil A, Das S, Owen H, Reddy PM, Ané JM, James EK, Gyaneshwar P. A rhamnose-deficient lipopolysaccharide mutant of Rhizobium sp. IRBG74 is defective in root colonization and beneficial interactions with its flooding-tolerant hosts Sesbania cannabina and wetland rice. JOURNAL OF EXPERIMENTAL BOTANY 2016; 67:5869-5884. [PMID: 27702995 DOI: 10.1093/jxb/erw354] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Rhizobium sp. IRBG74 develops a classical nitrogen-fixing symbiosis with the aquatic legume Sesbania cannabina (Retz.). It also promotes the growth of wetland rice (Oryza sativa L.), but little is known about the rhizobial determinants important for these interactions. In this study, we analyzed the colonization of S. cannabina and rice using a strain of Rhizobium sp. IRBG74 dually marked with β-glucuronidase and the green fluorescent protein. This bacterium colonized S. cannabina by crack entry and through root hair infection under flooded and non-flooded conditions, respectively. Rhizobium sp. IRBG74 colonized the surfaces of wetland rice roots, but also entered them at the base of lateral roots. It became endophytically established within intercellular spaces in the rice cortex, and intracellularly within epidermal and hypodermal cells. A mutant of Rhizobium sp. IRBG74 altered in the synthesis of the rhamnose-containing O-antigen exhibited significant defects, not only in nodulation and symbiotic nitrogen fixation with S. cannabina, but also in rice colonization and plant growth promotion. Supplementation with purified lipopolysaccharides from the wild-type strain, but not from the mutant, restored the beneficial colonization of rice roots, but not fully effective nodulation of S. cannabina Commonalities and differences in the rhizobial colonization of the roots of wetland legume and rice hosts are discussed.
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Affiliation(s)
- Shubhajit Mitra
- Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI 53211 USA
| | - Arijit Mukherjee
- Department of Agronomy, University of Wisconsin-Madison, Madison, WI, USA
| | - Audrey Wiley-Kalil
- Department of Agronomy, University of Wisconsin-Madison, Madison, WI, USA
| | - Seema Das
- Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI 53211 USA
| | - Heather Owen
- Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI 53211 USA
| | | | - Jean-Michel Ané
- Department of Agronomy, University of Wisconsin-Madison, Madison, WI, USA Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA
| | | | - Prasad Gyaneshwar
- Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI 53211 USA
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32
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An W, Guo F, Song Y, Gao N, Bai S, Dai J, Wei H, Zhang L, Yu D, Xia M, Yu Y, Qi M, Tian C, Chen H, Wu Z, Zhang T, Qiu D. Comparative genomics analyses on EPS biosynthesis genes required for floc formation of Zoogloea resiniphila and other activated sludge bacteria. WATER RESEARCH 2016; 102:494-504. [PMID: 27403872 DOI: 10.1016/j.watres.2016.06.058] [Citation(s) in RCA: 86] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Revised: 06/27/2016] [Accepted: 06/27/2016] [Indexed: 06/06/2023]
Abstract
Activated sludge (AS) process has been widely utilized for municipal sewage and industrial wastewater treatment. Zoolgoea and its related floc-forming bacteria are required for formation of AS flocs which is the key to gravitational effluent-and-sludge separation and AS recycling. However, little is known about the genetics, biochemistry and physiology of Zoogloea and its related bacteria. This report deals with the comparative genomic analyses on two Zoogloea resiniphila draft genomes and the closely related proteobacterial species commonly found in AS. In particular, the metabolic processes involved in removal of organic matters, nitrogen and phosphorus were analyzed. Furthermore, it is revealed that a large gene cluster, encoding eight glycosyltransferases and other proteins involved in biosynthesis and export of extracellular polysaccharides (EPS), was required for floc formation. One of the two asparagine synthase paralogues, associated with this EPS biosynthesis gene cluster, was required for floc formation in Zoogloea. Similar EPS biosynthesis gene cluster(s) were identified in the genome of other AS proteobacteria including polyphosphate-accumulating Candidatus Accumulibacter phosphatis (CAP) and nitrifying Nitrosopira and Nitrosomonas bacteria, but the gene composition varies interspecifically and intraspecifically. Our results indicate that floc formation of desired AS bacteria, including CAP strains, facilitate their recruitment into AS and gradual enrichment via repeated AS settling and recycling processes.
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Affiliation(s)
- Weixing An
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Feng Guo
- School of Life Sciences, Xiamen University, Xiamen 361005, China
| | - Yulong Song
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Na Gao
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Shijie Bai
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; Institute of Deep-sea Science and Technology, Chinese Academy of Sciences, Sanya 572000, China
| | - Jingcheng Dai
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Hehong Wei
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Liping Zhang
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Dianzhen Yu
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Ming Xia
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Ying Yu
- Institute for Genetics and Development, Chinese Academy of Sciences, Beijing 100101, China
| | - Ming Qi
- Institute for Genetics and Development, Chinese Academy of Sciences, Beijing 100101, China
| | - Chunyuan Tian
- School of Life Sciences and Technology, Hubei Engineering University, Xiaogan 43200, China
| | - Haofeng Chen
- Institute for Genetics and Development, Chinese Academy of Sciences, Beijing 100101, China
| | - Zhenbin Wu
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Tong Zhang
- Environmental Biotechnology Laboratory, Department of Civil Engineering, The University of Hong Kong, Pokfulam, Hong Kong.
| | - Dongru Qiu
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China.
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Regulation of Gene Expression in Shewanella oneidensis MR-1 during Electron Acceptor Limitation and Bacterial Nanowire Formation. Appl Environ Microbiol 2016; 82:5428-43. [PMID: 27342561 DOI: 10.1128/aem.01615-16] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Accepted: 06/22/2016] [Indexed: 12/12/2022] Open
Abstract
UNLABELLED In limiting oxygen as an electron acceptor, the dissimilatory metal-reducing bacterium Shewanella oneidensis MR-1 rapidly forms nanowires, extensions of its outer membrane containing the cytochromes MtrC and OmcA needed for extracellular electron transfer. RNA sequencing (RNA-Seq) analysis was employed to determine differential gene expression over time from triplicate chemostat cultures that were limited for oxygen. We identified 465 genes with decreased expression and 677 genes with increased expression. The coordinated increased expression of heme biosynthesis, cytochrome maturation, and transport pathways indicates that S. oneidensis MR-1 increases cytochrome production, including the transcription of genes encoding MtrA, MtrC, and OmcA, and transports these decaheme cytochromes across the cytoplasmic membrane during electron acceptor limitation and nanowire formation. In contrast, the expression of the mtrA and mtrC homologs mtrF and mtrD either remains unaffected or decreases under these conditions. The ompW gene, encoding a small outer membrane porin, has 40-fold higher expression during oxygen limitation, and it is proposed that OmpW plays a role in cation transport to maintain electrical neutrality during electron transfer. The genes encoding the anaerobic respiration regulator cyclic AMP receptor protein (CRP) and the extracytoplasmic function sigma factor RpoE are among the transcription factor genes with increased expression. RpoE might function by signaling the initial response to oxygen limitation. Our results show that RpoE activates transcription from promoters upstream of mtrC and omcA The transcriptome and mutant analyses of S. oneidensis MR-1 nanowire production are consistent with independent regulatory mechanisms for extending the outer membrane into tubular structures and for ensuring the electron transfer function of the nanowires. IMPORTANCE Shewanella oneidensis MR-1 has the capacity to transfer electrons to its external surface using extensions of the outer membrane called bacterial nanowires. These bacterial nanowires link the cell's respiratory chain to external surfaces, including oxidized metals important in bioremediation, and explain why S. oneidensis can be utilized as a component of microbial fuel cells, a form of renewable energy. In this work, we use differential gene expression analysis to focus on which genes function to produce the nanowires and promote extracellular electron transfer during oxygen limitation. Among the genes that are expressed at high levels are those encoding cytochrome proteins necessary for electron transfer. Shewanella coordinates the increased expression of regulators, metabolic pathways, and transport pathways to ensure that cytochromes efficiently transfer electrons along the nanowires.
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Differential Regulation of the Two Ferrochelatase Paralogues in Shewanella loihica PV-4 in Response to Environmental Stresses. Appl Environ Microbiol 2016; 82:5077-88. [PMID: 27287322 DOI: 10.1128/aem.00203-16] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Accepted: 06/06/2016] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Determining the function and regulation of paralogues is important in understanding microbial functional genomics and environmental adaptation. Heme homeostasis is crucial for the survival of environmental microorganisms. Most Shewanella species encode two paralogues of ferrochelatase, the terminal enzyme in the heme biosynthesis pathway. The function and transcriptional regulation of two ferrochelatase genes, hemH1 and hemH2, were investigated in Shewanella loihica PV-4. The disruption of hemH1 but not hemH2 resulted in a significant accumulation of extracellular protoporphyrin IX (PPIX), the precursor to heme, and decreased intracellular heme levels. hemH1 was constitutively expressed, and the expression of hemH2 increased when hemH1 was disrupted. The transcription of hemH1 was regulated by the housekeeping sigma factor RpoD and potentially regulated by OxyR, while hemH2 appeared to be regulated by the oxidative stress-associated sigma factor RpoE2. When an oxidative stress condition was mimicked by adding H2O2 to the medium or exposing the culture to light, PPIX accumulation was suppressed in the ΔhemH1 mutant. Consistently, transcriptome analysis indicated enhanced iron uptake and suppressed heme synthesis in the ΔhemH1 mutant. These data indicate that the two paralogues are functional in the heme synthesis pathway but regulated by environmental conditions, providing insights into the understanding of bacterial response to environmental stresses and a great potential to commercially produce porphyrin compounds. IMPORTANCE Shewanella is capable of utilizing a variety of electron acceptors for anaerobic respiration because of the existence of multiple c-type cytochromes in which heme is an essential component. The cytochrome-mediated electron transfer across cellular membranes could potentially be used for biotechnological purposes, such as electricity generation in microbial fuel cells and dye decolorization. However, the mechanism underlying the regulation of biosynthesis of heme and cytochromes is poorly understood. Our study has demonstrated that two ferrochelatase genes involved in heme biosynthesis are differentially regulated in response to environmental stresses, including light and reactive oxygen species. This is an excellent example showing how bacteria have evolved to maintain cellular heme homeostasis. More interestingly, the high yields of extracellular protoporphyrin IX by the Shewanella loihica PV-4 mutants could be utilized for commercial production of this valuable chemical via bacterial fermentation.
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De Novo Characterization of Genes That Contribute to High-Level Ciprofloxacin Resistance in Escherichia coli. Antimicrob Agents Chemother 2016; 60:6353-5. [PMID: 27431218 DOI: 10.1128/aac.00889-16] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Accepted: 07/06/2016] [Indexed: 01/07/2023] Open
Abstract
Sensitization of resistant bacteria to existing antibiotics depends on the identification of candidate targets whose activities contribute to resistance. Using a transposon insertion library in an Escherichia coli mutant that was 2,000 times less susceptible to ciprofloxacin than its parent and the relative fitness scores, we identified 19 genes that contributed to the acquired ciprofloxacin resistance and mapped the shortest genetic path that increased the antibiotic susceptibility of the resistant bacteria back to a near wild-type level.
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Zhu LP, Yue XJ, Han K, Li ZF, Zheng LS, Yi XN, Wang HL, Zhang YM, Li YZ. Allopatric integrations selectively change host transcriptomes, leading to varied expression efficiencies of exotic genes in Myxococcus xanthus. Microb Cell Fact 2015; 14:105. [PMID: 26194479 PMCID: PMC4509775 DOI: 10.1186/s12934-015-0294-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2015] [Accepted: 07/07/2015] [Indexed: 01/29/2023] Open
Abstract
Background Exotic genes, especially clustered multiple-genes for a complex pathway, are normally integrated into chromosome for heterologous expression. The influences of insertion sites on heterologous expression and allotropic expressions of exotic genes on host remain mostly unclear. Results We compared the integration and expression efficiencies of single and multiple exotic genes that were inserted into Myxococcus xanthus genome by transposition and attB-site-directed recombination. While the site-directed integration had a rather stable chloramphenicol acetyl transferase (CAT) activity, the transposition produced varied CAT enzyme activities. We attempted to integrate the 56-kb gene cluster for the biosynthesis of antitumor polyketides epothilones into M. xanthus genome by site-direction but failed, which was determined to be due to the insertion size limitation at the attB site. The transposition technique produced many recombinants with varied production capabilities of epothilones, which, however, were not paralleled to the transcriptional characteristics of the local sites where the genes were integrated. Comparative transcriptomics analysis demonstrated that the allopatric integrations caused selective changes of host transcriptomes, leading to varied expressions of epothilone genes in different mutants. Conclusions With the increase of insertion fragment size, transposition is a more practicable integration method for the expression of exotic genes. Allopatric integrations selectively change host transcriptomes, which lead to varied expression efficiencies of exotic genes. Electronic supplementary material The online version of this article (doi:10.1186/s12934-015-0294-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Li-Ping Zhu
- State Key Laboratory of Microbial Technology, School of Life Science, Shandong University, Jinan, 250100, China.
| | - Xin-Jing Yue
- State Key Laboratory of Microbial Technology, School of Life Science, Shandong University, Jinan, 250100, China.
| | - Kui Han
- State Key Laboratory of Microbial Technology, School of Life Science, Shandong University, Jinan, 250100, China.
| | - Zhi-Feng Li
- State Key Laboratory of Microbial Technology, School of Life Science, Shandong University, Jinan, 250100, China.
| | - Lian-Shuai Zheng
- State Key Laboratory of Microbial Technology, School of Life Science, Shandong University, Jinan, 250100, China.
| | - Xiu-Nan Yi
- State Key Laboratory of Microbial Technology, School of Life Science, Shandong University, Jinan, 250100, China.
| | - Hai-Long Wang
- State Key Laboratory of Microbial Technology, School of Life Science, Shandong University, Jinan, 250100, China.
| | - You-Ming Zhang
- State Key Laboratory of Microbial Technology, School of Life Science, Shandong University, Jinan, 250100, China.
| | - Yue-Zhong Li
- State Key Laboratory of Microbial Technology, School of Life Science, Shandong University, Jinan, 250100, China.
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Bonis BM, Gralnick JA. Marinobacter subterrani, a genetically tractable neutrophilic Fe(II)-oxidizing strain isolated from the Soudan Iron Mine. Front Microbiol 2015; 6:719. [PMID: 26236300 PMCID: PMC4503921 DOI: 10.3389/fmicb.2015.00719] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Accepted: 06/30/2015] [Indexed: 11/29/2022] Open
Abstract
We report the isolation, characterization, and development of a robust genetic system for a halophilic, Fe(II)-oxidizing bacterium isolated from a vertical borehole originating 714 m below the surface located in the Soudan Iron Mine in northern Minnesota, USA. Sequence analysis of the 16S rRNA gene places the isolate in the genus Marinobacter of the Gammaproteobacteria. The genome of the isolate was sequenced using a combination of short- and long-read technologies resulting in two contigs representing a 4.4 Mbp genome. Using genomic information, we used a suicide vector for targeted deletion of specific flagellin genes, resulting in a motility-deficient mutant. The motility mutant was successfully complemented by expression of the deleted genes in trans. Random mutagenesis using a transposon was also achieved. Capable of heterotrophic growth, this isolate represents a microaerophilic Fe(II)-oxidizing species for which a system for both directed and random mutagenesis has been established. Analysis of 16S rDNA suggests Marinobacter represents a major taxon in the mine, and genetic interrogation of this genus may offer insight into the structure of deep subsurface communities as well as an additional tool for analyzing nutrient and element cycling in the subsurface ecosystem.
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Affiliation(s)
- Benjamin M Bonis
- BioTechnology Institute and Department of Microbiology, University of Minnesota - Twin Cities , Saint Paul, MN, USA
| | - Jeffrey A Gralnick
- BioTechnology Institute and Department of Microbiology, University of Minnesota - Twin Cities , Saint Paul, MN, USA
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Barney BM, Eberhart LJ, Ohlert JM, Knutson CM, Plunkett MH. Gene Deletions Resulting in Increased Nitrogen Release by Azotobacter vinelandii: Application of a Novel Nitrogen Biosensor. Appl Environ Microbiol 2015; 81:4316-28. [PMID: 25888177 PMCID: PMC4475869 DOI: 10.1128/aem.00554-15] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Accepted: 04/13/2015] [Indexed: 11/20/2022] Open
Abstract
Azotobacter vinelandii is a widely studied model diazotrophic (nitrogen-fixing) bacterium and also an obligate aerobe, differentiating it from many other diazotrophs that require environments low in oxygen for the function of the nitrogenase. As a free-living bacterium, A. vinelandii has evolved enzymes and transporters to minimize the loss of fixed nitrogen to the surrounding environment. In this study, we pursued efforts to target specific enzymes and further developed screens to identify individual colonies of A. vinelandii producing elevated levels of extracellular nitrogen. Targeted deletions were done to convert urea into a terminal product by disrupting the urease genes that influence the ability of A. vinelandii to recycle the urea nitrogen within the cell. Construction of a nitrogen biosensor strain was done to rapidly screen several thousand colonies disrupted by transposon insertional mutagenesis to identify strains with increased extracellular nitrogen production. Several disruptions were identified in the ammonium transporter gene amtB that resulted in the production of sufficient levels of extracellular nitrogen to support the growth of the biosensor strain. Further studies substituting the biosensor strain with the green alga Chlorella sorokiniana confirmed that levels of nitrogen produced were sufficient to support the growth of this organism when the medium was supplemented with sufficient sucrose to support the growth of the A. vinelandii in coculture. The nature and quantities of nitrogen released by urease and amtB disruptions were further compared to strains reported in previous efforts that altered the nifLA regulatory system to produce elevated levels of ammonium. These results reveal alternative approaches that can be used in various combinations to yield new strains that might have further application in biofertilizer schemes.
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Affiliation(s)
- Brett M Barney
- Department of Bioproducts and Biosystems Engineering, University of Minnesota, St. Paul, Minnesota, USA Biotechnology Institute, University of Minnesota, St. Paul, Minnesota, USA
| | - Lauren J Eberhart
- Department of Bioproducts and Biosystems Engineering, University of Minnesota, St. Paul, Minnesota, USA Biotechnology Institute, University of Minnesota, St. Paul, Minnesota, USA
| | - Janet M Ohlert
- Department of Bioproducts and Biosystems Engineering, University of Minnesota, St. Paul, Minnesota, USA
| | - Carolann M Knutson
- Department of Bioproducts and Biosystems Engineering, University of Minnesota, St. Paul, Minnesota, USA
| | - Mary H Plunkett
- Department of Bioproducts and Biosystems Engineering, University of Minnesota, St. Paul, Minnesota, USA
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Rapid quantification of mutant fitness in diverse bacteria by sequencing randomly bar-coded transposons. mBio 2015; 6:e00306-15. [PMID: 25968644 PMCID: PMC4436071 DOI: 10.1128/mbio.00306-15] [Citation(s) in RCA: 239] [Impact Index Per Article: 26.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Transposon mutagenesis with next-generation sequencing (TnSeq) is a powerful approach to annotate gene function in bacteria, but existing protocols for TnSeq require laborious preparation of every sample before sequencing. Thus, the existing protocols are not amenable to the throughput necessary to identify phenotypes and functions for the majority of genes in diverse bacteria. Here, we present a method, random bar code transposon-site sequencing (RB-TnSeq), which increases the throughput of mutant fitness profiling by incorporating random DNA bar codes into Tn5 and mariner transposons and by using bar code sequencing (BarSeq) to assay mutant fitness. RB-TnSeq can be used with any transposon, and TnSeq is performed once per organism instead of once per sample. Each BarSeq assay requires only a simple PCR, and 48 to 96 samples can be sequenced on one lane of an Illumina HiSeq system. We demonstrate the reproducibility and biological significance of RB-TnSeq with Escherichia coli, Phaeobacter inhibens, Pseudomonas stutzeri, Shewanella amazonensis, and Shewanella oneidensis. To demonstrate the increased throughput of RB-TnSeq, we performed 387 successful genome-wide mutant fitness assays representing 130 different bacterium-carbon source combinations and identified 5,196 genes with significant phenotypes across the five bacteria. In P. inhibens, we used our mutant fitness data to identify genes important for the utilization of diverse carbon substrates, including a putative d-mannose isomerase that is required for mannitol catabolism. RB-TnSeq will enable the cost-effective functional annotation of diverse bacteria using mutant fitness profiling. A large challenge in microbiology is the functional assessment of the millions of uncharacterized genes identified by genome sequencing. Transposon mutagenesis coupled to next-generation sequencing (TnSeq) is a powerful approach to assign phenotypes and functions to genes. However, the current strategies for TnSeq are too laborious to be applied to hundreds of experimental conditions across multiple bacteria. Here, we describe an approach, random bar code transposon-site sequencing (RB-TnSeq), which greatly simplifies the measurement of gene fitness by using bar code sequencing (BarSeq) to monitor the abundance of mutants. We performed 387 genome-wide fitness assays across five bacteria and identified phenotypes for over 5,000 genes. RB-TnSeq can be applied to diverse bacteria and is a powerful tool to annotate uncharacterized genes using phenotype data.
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Estevez-Canales M, Kuzume A, Borjas Z, Füeg M, Lovley D, Wandlowski T, Esteve-Núñez A. A severe reduction in the cytochrome C content of Geobacter sulfurreducens eliminates its capacity for extracellular electron transfer. ENVIRONMENTAL MICROBIOLOGY REPORTS 2015; 7:219-226. [PMID: 25348891 DOI: 10.1111/1758-2229.12230] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Accepted: 09/23/2014] [Indexed: 06/04/2023]
Abstract
The ability of Geobacter species to transfer electrons outside the cell enables them to play an important role in a number of biogeochemical and bioenergy processes. Gene deletion studies have implicated periplasmic and outer-surface c-type cytochromes in this extracellular electron transfer. However, even when as many as five c-type cytochrome genes have been deleted, some capacity for extracellular electron transfer remains. In order to evaluate the role of c-type cytochromes in extracellular electron transfer, Geobacter sulfurreducens was grown in a low-iron medium that included the iron chelator (2,2'-bipyridine) to further sequester iron. Haem-staining revealed that the cytochrome content of cells grown in this manner was 15-fold lower than in cells exposed to a standard iron-containing medium. The low cytochrome abundance was confirmed by in situ nanoparticle-enhanced Raman spectroscopy (NERS). The cytochrome-depleted cells reduced fumarate to succinate as well as the cytochrome-replete cells do, but were unable to reduce Fe(III) citrate or to exchange electrons with a graphite electrode. These results demonstrate that c-type cytochromes are essential for extracellular electron transfer by G. sulfurreducens. The strategy for growing cytochrome-depleted G. sulfurreducens will also greatly aid future physiological studies of Geobacter species and other microorganisms capable of extracellular electron transfer.
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Affiliation(s)
- Marta Estevez-Canales
- Department of Chemical Engineering, University of Alcalá, Alcalá de Henares, Madrid, Spain
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Abstract
UNLABELLED Clostridium difficile infection (CDI) is dramatically increasing as a cause of antibiotic- and hospital-associated diarrhea worldwide. C. difficile, a multidrug-resistant pathogen, flourishes in the colon after the gut microbiota has been altered by antibiotic therapy. Consequently, it produces toxins A and B that directly cause disease. Despite the enormous public health problem posed by this pathogen, the molecular mechanisms that regulate production of the toxins, which are directly responsible for disease, remained largely unknown until now. Here, we show that C. difficile toxin synthesis is regulated by an accessory gene regulator quorum-signaling system, which is mediated through a small (<1,000-Da) thiolactone that can be detected directly in stools of CDI patients. These findings provide direct evidence of the mechanism of regulation of C. difficile toxin synthesis and offer exciting new avenues both for rapid detection of C. difficile infection and development of quorum-signaling-based non-antibiotic therapies to combat this life-threatening emerging pathogen. IMPORTANCE Clostridium difficile infection (CDI) is the most common definable cause of hospital-acquired and antibiotic-associated diarrhea in the United States, with the total cost of treatment estimated between 1 and 4.8 billion U.S. dollars annually. C. difficile, a Gram-positive, spore-forming anaerobe, flourishes in the colon after the gut microbiota has been altered by antibiotic therapy. As a result, there is an urgent need for non-antibiotic CDI treatments that preserve the colonic microbiota. C. difficile produces toxins A and B, which are directly responsible for disease. Here, we report that C. difficile regulates its toxin synthesis by quorum signaling, in which a novel signaling peptide activates transcription of the disease-causing toxin genes. This finding provides new therapeutic targets to be harnessed for novel nonantibiotic therapy for C. difficile infections.
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Elizabethkingia anophelis: molecular manipulation and interactions with mosquito hosts. Appl Environ Microbiol 2015; 81:2233-43. [PMID: 25595771 DOI: 10.1128/aem.03733-14] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Flavobacteria (members of the family Flavobacteriaceae) dominate the bacterial community in the Anopheles mosquito midgut. One such commensal, Elizabethkingia anophelis, is closely associated with Anopheles mosquitoes through transstadial persistence (i.e., from one life stage to the next); these and other properties favor its development for paratransgenic applications in control of malaria parasite transmission. However, the physiological requirements of E. anophelis have not been investigated, nor has its capacity to perpetuate despite digestion pressure in the gut been quantified. To this end, we first developed techniques for genetic manipulation of E. anophelis, including selectable markers, reporter systems (green fluorescent protein [GFP] and NanoLuc), and transposons that function in E. anophelis. A flavobacterial expression system based on the promoter PompA was integrated into the E. anophelis chromosome and showed strong promoter activity to drive GFP and NanoLuc reporter production. Introduced, GFP-tagged E. anophelis associated with mosquitoes at successive developmental stages and propagated in Anopheles gambiae and Anopheles stephensi but not in Aedes triseriatus mosquitoes. Feeding NanoLuc-tagged cells to A. gambiae and A. stephensi in the larval stage led to infection rates of 71% and 82%, respectively. In contrast, a very low infection rate (3%) was detected in Aedes triseriatus mosquitoes under the same conditions. Of the initial E. anophelis cells provided to larvae, 23%, 71%, and 85% were digested in A. stephensi, A. gambiae, and Aedes triseriatus, respectively, demonstrating that E. anophelis adapted to various mosquito midgut environments differently. Bacterial cell growth increased up to 3-fold when arginine was supplemented in the defined medium. Furthermore, the number of NanoLuc-tagged cells in A. stephensi significantly increased when arginine was added to a sugar diet, showing it to be an important amino acid for E. anophelis. Animal erythrocytes promoted E. anophelis growth in vivo and in vitro, indicating that this bacterium could obtain nutrients by participating in erythrocyte lysis in the mosquito midgut.
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Petersen LM, Tisa LS. Molecular characterization of protease activity in Serratia sp. strain SCBI and its importance in cytotoxicity and virulence. J Bacteriol 2014; 196:3923-36. [PMID: 25182493 PMCID: PMC4248818 DOI: 10.1128/jb.01908-14] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Accepted: 08/26/2014] [Indexed: 01/19/2023] Open
Abstract
A newly recognized Serratia species, termed South African Caenorhabditis briggsae isolate (SCBI), is both a mutualist of the nematode Caenorhabditis briggsae KT0001 and a pathogen of lepidopteran insects. Serratia sp. strain SCBI displays high proteolytic activity, and because secreted proteases are known virulence factors for many pathogens, the purpose of this study was to identify genes essential for extracellular protease activity in Serratia sp. strain SCBI and to determine what role proteases play in insect pathogenesis and cytotoxicity. A bank of 2,100 transposon mutants was generated, and six SCBI mutants with defective proteolytic activity were identified. These mutants were also defective in cytotoxicity. The mutants were found defective in genes encoding the following proteins: alkaline metalloprotease secretion protein AprE, a BglB family transcriptional antiterminator, an inosine/xanthosine triphosphatase, GidA, a methyl-accepting chemotaxis protein, and a PIN domain protein. Gene expression analysis on these six mutants showed significant downregulation in mRNA levels of several different types of predicted protease genes. In addition, transcriptome sequencing (RNA-seq) analysis provided insight into how inactivation of AprE, GidA, and a PIN domain protein influences motility and virulence, as well as protease activity. Using quantitative reverse transcription-PCR (qRT-PCR) to further characterize expression of predicted protease genes in wild-type Serratia sp. SCBI, the highest mRNA levels for the alkaline metalloprotease genes (termed prtA1 to prtA4) occurred following the death of an insect host, while two serine protease and two metalloprotease genes had their highest mRNA levels during active infection. Overall, these results indicate that proteolytic activity is essential for cytotoxicity in Serratia sp. SCBI and that its regulation appears to be highly complex.
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Affiliation(s)
- Lauren M Petersen
- Department of Molecular, Cellular, and Biomedical Sciences, University of New Hampshire, Durham, New Hampshire, USA
| | - Louis S Tisa
- Department of Molecular, Cellular, and Biomedical Sciences, University of New Hampshire, Durham, New Hampshire, USA
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Brennan CM, Mazzucca NQ, Mezoian T, Hunt TM, Keane ML, Leonard JN, Scola SE, Beer EN, Perdue S, Pellock BJ. Reduced heme levels underlie the exponential growth defect of the Shewanella oneidensis hfq mutant. PLoS One 2014; 9:e109879. [PMID: 25356668 PMCID: PMC4214671 DOI: 10.1371/journal.pone.0109879] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Accepted: 09/03/2014] [Indexed: 11/18/2022] Open
Abstract
The RNA chaperone Hfq fulfills important roles in small regulatory RNA (sRNA) function in many bacteria. Loss of Hfq in the dissimilatory metal reducing bacterium Shewanella oneidensis strain MR-1 results in slow exponential phase growth and a reduced terminal cell density at stationary phase. We have found that the exponential phase growth defect of the hfq mutant in LB is the result of reduced heme levels. Both heme levels and exponential phase growth of the hfq mutant can be completely restored by supplementing LB medium with 5-aminolevulinic acid (5-ALA), the first committed intermediate synthesized during heme synthesis. Increasing expression of gtrA, which encodes the enzyme that catalyzes the first step in heme biosynthesis, also restores heme levels and exponential phase growth of the hfq mutant. Taken together, our data indicate that reduced heme levels are responsible for the exponential growth defect of the S. oneidensis hfq mutant in LB medium and suggest that the S. oneidensis hfq mutant is deficient in heme production at the 5-ALA synthesis step.
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Affiliation(s)
- Christopher M. Brennan
- Department of Biology, Providence College, Providence, Rhode Island, United States of America
| | - Nicholas Q. Mazzucca
- Department of Biology, Providence College, Providence, Rhode Island, United States of America
| | - Taylor Mezoian
- Department of Biology, Providence College, Providence, Rhode Island, United States of America
| | - Taylor M. Hunt
- Department of Biology, Providence College, Providence, Rhode Island, United States of America
| | - Meaghan L. Keane
- Department of Biology, Providence College, Providence, Rhode Island, United States of America
| | - Jessica N. Leonard
- Department of Biology, Providence College, Providence, Rhode Island, United States of America
| | - Shelby E. Scola
- Department of Chemistry and Biochemistry, Providence College, Providence, Rhode Island, United States of America
| | - Emma N. Beer
- Department of Biology, Providence College, Providence, Rhode Island, United States of America
| | - Sarah Perdue
- Department of Biology, Providence College, Providence, Rhode Island, United States of America
| | - Brett J. Pellock
- Department of Biology, Providence College, Providence, Rhode Island, United States of America
- * E-mail:
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Wu X, Zeng Q, Koestler BJ, Waters CM, Sundin GW, Hutchins W, Yang CH. Deciphering the components that coordinately regulate virulence factors of the soft rot pathogen Dickeya dadantii. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2014; 27:1119-1131. [PMID: 25180688 DOI: 10.1094/mpmi-01-14-0026-r] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The bacterial soft rot pathogen Dickeya dadantii utilizes the type III secretion system (T3SS) to suppress host defense responses, and secretes pectate lyase (Pel) to disintegrate the plant cell wall. A transposon mutagenesis fluorescence-activated cell sorting screen was used to identify mutants with altered promoter activities of the T3SS pilus gene hrpA. Several insertion mutations, resulting in changes in hrpA expression, were mapped to a new locus, opgGH, which encodes the gene cluster responsible for osmoregulated periplasmic glucan (OPG) synthesis proteins. Our data showed that OPG was involved in T3SS and Pel regulation by altering the expression of the regulatory small RNA RsmB. Through genome searching, the mechanism of two novel regulatory components, the RcsCD-RcsB phosphorelay and CsrD on OPG and the rsmB gene, was further investigated. The Rcs phosphorelay and OPG inversely regulated rsmB at transcriptional and post-transcriptional levels, respectively. CsrD exhibited dual functionality in T3SS and Pel regulation by manipulating levels of RsmB RNA and cyclic diguanylate monophosphate (c-di-GMP). CsrD positively regulated the promoter activity of the rsmB gene but negatively controlled RsmB RNA at the post-transcriptional level via OpgGH. In addition, CsrD contains both GGDEF and EAL domains but acted as a c-di-GMP phosphodiesterase. When the expression of the csrD gene was induced, CsrD regulated T3SS expression and Pel production through controlling intracellular c-di-GMP levels.
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Genome-scale metabolic network validation of Shewanella oneidensis using transposon insertion frequency analysis. PLoS Comput Biol 2014; 10:e1003848. [PMID: 25233219 PMCID: PMC4168976 DOI: 10.1371/journal.pcbi.1003848] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Accepted: 08/07/2014] [Indexed: 01/08/2023] Open
Abstract
Transposon mutagenesis, in combination with parallel sequencing, is becoming a powerful tool for en-masse mutant analysis. A probability generating function was used to explain observed miniHimar transposon insertion patterns, and gene essentiality calls were made by transposon insertion frequency analysis (TIFA). TIFA incorporated the observed genome and sequence motif bias of the miniHimar transposon. The gene essentiality calls were compared to: 1) previous genome-wide direct gene-essentiality assignments; and, 2) flux balance analysis (FBA) predictions from an existing genome-scale metabolic model of Shewanella oneidensis MR-1. A three-way comparison between FBA, TIFA, and the direct essentiality calls was made to validate the TIFA approach. The refinement in the interpretation of observed transposon insertions demonstrated that genes without insertions are not necessarily essential, and that genes that contain insertions are not always nonessential. The TIFA calls were in reasonable agreement with direct essentiality calls for S. oneidensis, but agreed more closely with E. coli essentiality calls for orthologs. The TIFA gene essentiality calls were in good agreement with the MR-1 FBA essentiality predictions, and the agreement between TIFA and FBA predictions was substantially better than between the FBA and the direct gene essentiality predictions.
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Electroactive bacteria—molecular mechanisms and genetic tools. Appl Microbiol Biotechnol 2014; 98:8481-95. [DOI: 10.1007/s00253-014-6005-z] [Citation(s) in RCA: 153] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Revised: 07/28/2014] [Accepted: 07/30/2014] [Indexed: 12/15/2022]
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Transposon and deletion mutagenesis of genes involved in perchlorate reduction in Azospira suillum PS. mBio 2013; 5:e00769-13. [PMID: 24381299 PMCID: PMC3884062 DOI: 10.1128/mbio.00769-13] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
UNLABELLED Although much work on the biochemistry of the key enzymes of bacterial perchlorate reduction, chlorite dismutase, and perchlorate reductase has been published, understanding of the molecular mechanisms of this metabolism has been somewhat hampered by the lack of a clear model system amenable to genetic manipulation. Using transposon mutagenesis and clean deletions, genes important for perchlorate reduction in Azospira suillum PS have been identified both inside and outside the previously described perchlorate reduction genomic island (PRI). Transposon mutagenesis identified 18 insertions in 11 genes that completely abrogate growth via reduction of perchlorate but have no phenotype during denitrification. Of the mutants deficient in perchlorate reduction, 14 had insertions that were mapped to eight different genes within the PRI, highlighting its importance in this metabolism. To further explore the role of these genes, we also developed systems for constructing unmarked deletions and for complementing these deletions. Using these tools, every core gene in the PRI was systematically deleted; 8 of the 17 genes conserved in the PRI are essential for perchlorate respiration, including 3 genes that comprise a unique histidine kinase system. Interestingly, the other 9 genes in the PRI are not essential for perchlorate reduction and may thus have unknown functions during this metabolism. We present a model detailing our current understanding of perchlorate reduction that incorporates new concepts about this metabolism. IMPORTANCE Although perchlorate is generated naturally in the environment, groundwater contamination is largely a result of industrial activity. Bacteria capable of respiring perchlorate and remediating contaminated water have been isolated, but relatively little is known about the biochemistry and genetics of this process. Here we used two complementary approaches to identify genes involved in perchlorate reduction. Most of these genes are located on a genomic island, which is potentially capable of moving between organisms. Some of the genes identified are known to be directly involved in the metabolism of perchlorate, but other new genes likely regulate the metabolism in response to environmental signals. This work has uncovered new questions about the regulation, energetics, and evolution of perchlorate reduction but also presents the tools to address them.
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Brutinel ED, Gralnick JA. Anomalies of the anaerobic tricarboxylic acid cycle inShewanella oneidensisrevealed by Tn-seq. Mol Microbiol 2012; 86:273-83. [DOI: 10.1111/j.1365-2958.2012.08196.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/30/2012] [Indexed: 11/27/2022]
Affiliation(s)
- Evan D. Brutinel
- BioTechnology Institute and Department of Microbiology; University of Minnesota-Twin Cities; St Paul; MN; 55108; USA
| | - Jeffrey A. Gralnick
- BioTechnology Institute and Department of Microbiology; University of Minnesota-Twin Cities; St Paul; MN; 55108; USA
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A new locus affects cell motility, cellulose binding, and degradation by Cytophaga hutchinsonii. Appl Microbiol Biotechnol 2012; 96:161-70. [PMID: 22543350 DOI: 10.1007/s00253-012-4051-y] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2012] [Revised: 03/19/2012] [Accepted: 03/22/2012] [Indexed: 10/28/2022]
Abstract
Cytophaga hutchinsonii is a Gram-negative gliding bacterium, which can rapidly degrade crystalline cellulose via a novel strategy without any recognizable processive cellulases. Its mechanism of cellulose binding and degradation is still a mystery. In this study, the mutagenesis of C. hutchinsonii with the mariner-based transposon HimarEm3 and gene complementation with the oriC-based plasmid carrying the antibiotic resistance gene cfxA or tetQ were reported for the first time to provide valuable tools for mutagenesis and genetic manipulation of the bacterium. Mutant A-4 with a transposon mutation in gene CHU_0134, which encodes a putative thiol-disulfide isomerase exhibits defects in cell motility and cellulose degradation. The cellulose binding ability of A-4 was only half of that of the wild-type strain, while the endo-cellulase activity of the cell-free supernatants and on the intact cell surface of A-4 decreased by 40%. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of proteins binding to cellulose in the outer membrane showed that most of them were significantly decreased or disappeared in A-4 including some Gld proteins and hypothetical proteins, indicating that these proteins might play an important role in cell motility and cellulose binding and degradation by the bacterium.
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