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Chaudhary S, Ali W, Yadav M, Singh G, Gupta N, Grover S, Ghosh C, Chandra S, Rathore JS. Computational exploration of the genomic assignments, molecular structure, and dynamics of the ccdABXn2 toxin-antitoxin homolog with its bacterial target, the DNA gyrase, in the entomopathogen Xenorhabdus nematophila. J Biomol Struct Dyn 2024:1-15. [PMID: 38321949 DOI: 10.1080/07391102.2024.2311337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Accepted: 01/23/2024] [Indexed: 02/08/2024]
Abstract
Toxin-antitoxin (TA) modules, initially discovered on bacterial plasmids and subsequently identified within chromosomal contexts, hold a pivotal role in the realm of bacterial physiology. Among these, the pioneering TA system, ccd (Control of Cell Death), primarily localized on the F-plasmid, is known for its orchestration of plasmid replication with cellular division. Nonetheless, the precise functions of such systems within bacterial chromosomal settings remain a compelling subject that demands deeper investigation. To bridge this knowledge gap, our study focuses on exploring ccdABXn2, a chromosomally encoded TA module originating from the entomopathogenic bacterium Xenorhabdus nematophila. We meticulously delved into the system's genomic assignments, structural attributes, and functional interplay. Our findings uncovered intriguing patterns-CcdB toxin homologs exhibited higher conservation levels compared to their CcdA antitoxin counterparts. Moreover, we constructed secondary as well as tertiary models for both the CcdB toxin and CcdA antitoxin using threading techniques and subsequently validated their structural integrity. Our exploration extended to the identification of key interactions, including the peptide interaction with gyrase for the CcdB homolog and CcdB toxin interactions for the CcdA homolog, highlighting the intricate TA interaction network. Through docking and simulation analyses, we unequivocally demonstrated the inhibition of replication via binding the CcdB toxin to its target, DNA gyrase. These insights provide valuable knowledge about the metabolic and physiological roles of the chromosomally encoded ccdABXn2 TA module within the context of X. nematophila, significantly enhancing our comprehension of its functional significance within the intricate ecosystem of the bacterial host.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Shobhi Chaudhary
- School of Biotechnology, Gautam Buddha University, Greater Noida, India
| | - Waseem Ali
- Department of Molecular Medicine, Jamia Hamdard, New Delhi, India
| | - Mohit Yadav
- School of Biotechnology, Gautam Buddha University, Greater Noida, India
- Department of Molecular Biology and Biotechnology, Tezpur University, Assam, India
| | - Garima Singh
- School of Biotechnology, Gautam Buddha University, Greater Noida, India
| | - Nomita Gupta
- School of Biotechnology, Gautam Buddha University, Greater Noida, India
| | - Sonam Grover
- Department of Molecular Medicine, Jamia Hamdard, New Delhi, India
| | - Chaitali Ghosh
- Department of Zoology, Gargi College, University of Delhi, New Delhi, India
| | - Subhash Chandra
- Computational Biology & Biotechnology Laboratory, Department of Botany, Soban Singh Jeena University, Almora, India
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Jin G, Kim IH, Kim Y. The Lrp transcriptional factor of an entomopathogenic bacterium, Xenorhabdus hominickii, activates non-ribosomal peptide synthetases to suppress insect immunity. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2024; 151:105101. [PMID: 38000489 DOI: 10.1016/j.dci.2023.105101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Revised: 11/11/2023] [Accepted: 11/17/2023] [Indexed: 11/26/2023]
Abstract
Two bacterial genera, Xenorhabdus and Photorhabdus, are mutually symbiotic to the entomopathogenic nematodes, Steinernema and Heterorhabditis, respectively. The infective juveniles deliver the symbiotic bacteria to the hemocoel of target insects, in which the bacteria proliferate and help the development of the host nematode. The successful parasitism of the nematode-bacterial complex depends on host immunosuppression by the bacteria via their secondary metabolites. Leucine-responsive regulatory protein (Lrp) is a global bacterial transcriptional factor that plays a crucial role in parasitism. However, its regulatory targets to suppress insect immunity are not clearly understood. This study investigated the bacterial genes regulated by Lrp and the subsequent production of secondary metabolites in Xenorhabdus hominickii. Lrp expression occurred at the early infection stage of the bacteria in a target insect, Spodoptera exigua. A preliminary in silico screening indicated that 3.7% genes among 4075 predicted genes encoded in X. hominickii had the Lrp-response element on their promoters, including two non-ribosomal peptide synthetases (NRPSs). Eight NRPS (NRPS1-NRPS8) genes were predicted in the bacterial genome, in which six NRPS (NRPS3-NRPS8) expressions were positively correlated with Lrp expression in the infected larvae of S. exigua. Exchange of the Lrp promoter with an inducible promoter altered the production of the secondary metabolites and the NRPS expression levels. The immunosuppressive activities of X. hominickii were dependent on the Lrp expression level. The metabolites produced by Lrp expression included the eicosanoid-biosynthesis inhibitors and hemolytic factors. A cyclic dipeptide (=cPF) was produced by the bacteria at high Lrp expression and inhibited the phospholipase A2 activity of S. exigua in a competitive inhibitory manner. These results suggest that Lrp is a global transcriptional factor of X. hominickii and plays a crucial role in insect immunosuppression by modulating NRPS expression.
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Affiliation(s)
- Gahyeon Jin
- Department of Plant Medicals, Andong National University, Andong, 36729, South Korea
| | - Il-Hwan Kim
- Korea Research Institute of Standards and Science, Daejeon, 34113, South Korea
| | - Yonggyun Kim
- Department of Plant Medicals, Andong National University, Andong, 36729, South Korea.
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Ünal M, Yüksel E, Canhilal R. Biocontrol potential of cell suspensions and cell-free superntants of different Xenorhabdus and Photorhabdus bacteria against the different larval instars of Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae). Exp Parasitol 2022; 242:108394. [PMID: 36179855 DOI: 10.1016/j.exppara.2022.108394] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2022] [Revised: 09/21/2022] [Accepted: 09/23/2022] [Indexed: 12/01/2022]
Abstract
The black cutworm (BCW), Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae), is one of the destructive cutworm species. Black cutworm is a highly polyphagous pest that feeds on more than 30 plants, many of which are of economic importance such as maize, sugar beet, and potato. The control of BCW larvae relies heavily on the application of synthetic insecticides which have a detrimental impact on human health and the natural environment. In addition, increasing insecticide resistance in many insect species requires a novel and sustainable approach to controlling insect pests. The endosymbionts of entomopathogenic nematodes (EPNs) (Xenorhabdus and Phorohabdus spp.) represent a newly emerging green approach to controlling a wide range of insect pests. In the current study, the oral and contact efficacy of cell suspension (4 × 107 cells ml-1) and cell-free supernatants of different symbiotic bacteria (X. nematophilai, X. bovienii, X. budapestensis, and P. luminescent subsp. kayaii) were evaluated against the mixed groups of 1st-2nd and 3rd-4th instars larvae of BCW under controlled conditions. The oral treatment of the cell suspension and cell-free supernatants resulted in higher mortality rates than contact treatments. In general, larval mortality was higher in the 1st-2nd instar larvae than in the 3rd-4th instar larvae. The highest (75%) mortality was obtained from the cell suspension of X. budapestensis. The results indicated that the oral formulations of the cell suspension and cell-free supernatants of bacterial strains may have a good control potential against the 1st-2nd larvae BCW. However, the efficacy of the cell suspension and cell-free supernatants of tested bacterial strains should be further evaluated under greenhouse and field conditions.
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Affiliation(s)
- Merve Ünal
- Department of Plant Protection, Faculty of Agriculture, Erciyes University, 38030, Melikgazi, Kayseri, Turkey
| | - Ebubekir Yüksel
- Department of Plant Protection, Faculty of Agriculture, Erciyes University, 38030, Melikgazi, Kayseri, Turkey.
| | - Ramazan Canhilal
- Department of Plant Protection, Faculty of Agriculture, Erciyes University, 38030, Melikgazi, Kayseri, Turkey
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Apex Predator Nematodes and Meso-Predator Bacteria Consume Their Basal Insect Prey through Discrete Stages of Chemical Transformations. mSystems 2022; 7:e0031222. [PMID: 35543104 PMCID: PMC9241642 DOI: 10.1128/msystems.00312-22] [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
Microbial symbiosis drives physiological processes of higher-order systems, including the acquisition and consumption of nutrients that support symbiotic partner reproduction. Metabolic analytics provide new avenues to examine how chemical ecology, or the conversion of existing biomass to new forms, changes over a symbiotic life cycle. We applied these approaches to the nematode Steinernema carpocapsae, its mutualist bacterium, Xenorhabdus nematophila, and the insects they infect. The nematode-bacterium pair infects, kills, and reproduces in an insect until nutrients are depleted. To understand the conversion of insect biomass over time into either nematode or bacterium biomass, we integrated information from trophic, metabolomic, and gene regulation analyses. Trophic analysis established bacteria as meso-predators and primary insect consumers. Nematodes hold a trophic position of 4.6, indicative of an apex predator, consuming bacteria and likely other nematodes. Metabolic changes associated with Galleria mellonella insect bioconversion were assessed using multivariate statistical analyses of metabolomics data sets derived from sampling over an infection time course. Statistically significant, discrete phases were detected, indicating the insect chemical environment changes reproducibly during bioconversion. A novel hierarchical clustering method was designed to probe molecular abundance fluctuation patterns over time, revealing distinct metabolite clusters that exhibit similar abundance shifts across the time course. Composite data suggest bacterial tryptophan and nematode kynurenine pathways are coordinated for reciprocal exchange of tryptophan and NAD+ and for synthesis of intermediates that can have complex effects on bacterial phenotypes and nematode behaviors. Our analysis of pathways and metabolites reveals the chemistry underlying the recycling of organic material during carnivory. IMPORTANCE The processes by which organic life is consumed and reborn in a complex ecosystem were investigated through a multiomics approach applied to the tripartite Xenorhabdus bacterium-Steinernema nematode-Galleria insect symbiosis. Trophic analyses demonstrate the primary consumers of the insect are the bacteria, and the nematode in turn consumes the bacteria. This suggests the Steinernema-Xenorhabdus mutualism is a form of agriculture in which the nematode cultivates the bacterial food sources by inoculating them into insect hosts. Metabolomics analysis revealed a shift in biological material throughout progression of the life cycle: active infection, insect death, and conversion of cadaver tissues into bacterial biomass and nematode tissue. We show that each phase of the life cycle is metabolically distinct, with significant differences including those in the tricarboxylic acid cycle and amino acid pathways. Our findings demonstrate that symbiotic life cycles can be defined by reproducible stage-specific chemical signatures, enhancing our broad understanding of metabolic processes that underpin a three-way symbiosis.
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Grossman AS, Escobar CA, Mans EJ, Mucci NC, Mauer TJ, Jones KA, Moore CC, Abraham PE, Hettich RL, Schneider L, Campagna SR, Forest KT, Goodrich-Blair H. A Surface Exposed, Two-Domain Lipoprotein Cargo of a Type XI Secretion System Promotes Colonization of Host Intestinal Epithelia Expressing Glycans. Front Microbiol 2022; 13:800366. [PMID: 35572647 PMCID: PMC9100927 DOI: 10.3389/fmicb.2022.800366] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Accepted: 03/07/2022] [Indexed: 11/17/2022] Open
Abstract
The only known required component of the newly described Type XI secretion system (TXISS) is an outer membrane protein (OMP) of the DUF560 family. TXISSOMPs are broadly distributed across proteobacteria, but properties of the cargo proteins they secrete are largely unexplored. We report biophysical, histochemical, and phenotypic evidence that Xenorhabdus nematophila NilC is surface exposed. Biophysical data and structure predictions indicate that NilC is a two-domain protein with a C-terminal, 8-stranded β-barrel. This structure has been noted as a common feature of TXISS effectors and may be important for interactions with the TXISSOMP. The NilC N-terminal domain is more enigmatic, but our results indicate it is ordered and forms a β-sheet structure, and bioinformatics suggest structural similarities to carbohydrate-binding proteins. X. nematophila NilC and its presumptive TXISSOMP partner NilB are required for colonizing the anterior intestine of Steinernema carpocapsae nematodes: the receptacle of free-living, infective juveniles and the anterior intestinal cecum (AIC) in juveniles and adults. We show that, in adult nematodes, the AIC expresses a Wheat Germ Agglutinin (WGA)-reactive material, indicating the presence of N-acetylglucosamine or N-acetylneuraminic acid sugars on the AIC surface. A role for this material in colonization is supported by the fact that exogenous addition of WGA can inhibit AIC colonization by X. nematophila. Conversely, the addition of exogenous purified NilC increases the frequency with which X. nematophila is observed at the AIC, demonstrating that abundant extracellular NilC can enhance colonization. NilC may facilitate X. nematophila adherence to the nematode intestinal surface by binding to host glycans, it might support X. nematophila nutrition by cleaving sugars from the host surface, or it might help protect X. nematophila from nematode host immunity. Proteomic and metabolomic analyses of wild type X. nematophila compared to those lacking nilB and nilC revealed differences in cell wall and secreted polysaccharide metabolic pathways. Additionally, purified NilC is capable of binding peptidoglycan, suggesting that periplasmic NilC may interact with the bacterial cell wall. Overall, these findings support a model that NilB-regulated surface exposure of NilC mediates interactions between X. nematophila and host surface glycans during colonization. This is a previously unknown function for a TXISS.
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Affiliation(s)
- Alex S. Grossman
- Department of Microbiology, The University of Tennessee, Knoxville, Knoxville, TN, United States
| | - Cristian A. Escobar
- Department of Bacteriology, The University of Wisconsin–Madison, Madison, WI, United States
| | - Erin J. Mans
- Department of Microbiology, The University of Tennessee, Knoxville, Knoxville, TN, United States
| | - Nicholas C. Mucci
- Department of Microbiology, The University of Tennessee, Knoxville, Knoxville, TN, United States
| | - Terra J. Mauer
- Department of Bacteriology, The University of Wisconsin–Madison, Madison, WI, United States
| | - Katarina A. Jones
- Department of Chemistry, The University of Tennessee, Knoxville, Knoxville, TN, United States
| | - Cameron C. Moore
- Department of Microbiology, The University of Tennessee, Knoxville, Knoxville, TN, United States
| | - Paul E. Abraham
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, United States
| | - Robert L. Hettich
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, United States
| | - Liesel Schneider
- Department of Animal Sciences, The University of Tennessee, Knoxville, Knoxville, TN, United States
| | - Shawn R. Campagna
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, United States
- Biological and Small Molecule Mass Spectrometry Core, The University of Tennessee, Knoxville, Knoxville, TN, United States
- The University of Tennessee Oak Ridge Innovation Institute, Knoxville, TN, United States
| | - Katrina T. Forest
- Department of Bacteriology, The University of Wisconsin–Madison, Madison, WI, United States
- Katrina T. Forest,
| | - Heidi Goodrich-Blair
- Department of Microbiology, The University of Tennessee, Knoxville, Knoxville, TN, United States
- Department of Bacteriology, The University of Wisconsin–Madison, Madison, WI, United States
- *Correspondence: Heidi Goodrich-Blair,
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6
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Sánchez-Romero MA, Casadesús J. Waddington's Landscapes in the Bacterial World. Front Microbiol 2021; 12:685080. [PMID: 34149674 PMCID: PMC8212987 DOI: 10.3389/fmicb.2021.685080] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Accepted: 04/20/2021] [Indexed: 11/24/2022] Open
Abstract
Conrad Waddington’s epigenetic landscape, a visual metaphor for the development of multicellular organisms, is appropriate to depict the formation of phenotypic variants of bacterial cells. Examples of bacterial differentiation that result in morphological change have been known for decades. In addition, bacterial populations contain phenotypic cell variants that lack morphological change, and the advent of fluorescent protein technology and single-cell analysis has unveiled scores of examples. Cell-specific gene expression patterns can have a random origin or arise as a programmed event. When phenotypic cell-to-cell differences are heritable, bacterial lineages are formed. The mechanisms that transmit epigenetic states to daughter cells can have strikingly different levels of complexity, from the propagation of simple feedback loops to the formation of complex DNA methylation patterns. Game theory predicts that phenotypic heterogeneity can facilitate bacterial adaptation to hostile or unpredictable environments, serving either as a division of labor or as a bet hedging that anticipates future challenges. Experimental observation confirms the existence of both types of strategies in the bacterial world.
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Affiliation(s)
| | - Josep Casadesús
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain
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Faucher C, Mazana V, Kardacz M, Parthuisot N, Ferdy JB, Duneau D. Step-Specific Adaptation and Trade-Off over the Course of an Infection by GASP Mutation Small Colony Variants. mBio 2021; 12:e01399-20. [PMID: 33436427 PMCID: PMC7845629 DOI: 10.1128/mbio.01399-20] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Accepted: 11/17/2020] [Indexed: 11/20/2022] Open
Abstract
During an infection, parasites face a succession of challenges, each decisive for disease outcome. The diversity of challenges requires a series of parasite adaptations to successfully multiply and transmit from host to host. Thus, the pathogen genotypes that succeed during one step might be counterselected in later stages of the infection. Using the bacterium Xenorhabdus nematophila and adult Drosophila melanogaster flies as hosts, we showed that such step-specific adaptations, here linked to GASP (i.e., growth advantage in stationary phase) mutations in the X. nematophila master gene regulator lrp, exist and can trade off with each other. We found that nonsense lrp mutations had lowered the ability to resist the host immune response, while all classes of mutations in lrp were associated with a decrease in the ability to proliferate during early infection. We demonstrate that reduced proliferation of X. nematophila best explains diminished virulence in this infection model. Finally, decreased proliferation during the first step of infection is accompanied by improved proliferation during late infection, suggesting a trade-off between the adaptations to each step. Step-specific adaptations could play a crucial role in the chronic phase of infections in any disease organisms that show similar small colony variants (SCVs) to X. nematophilaIMPORTANCE Within-host evolution has been described in many bacterial diseases, and the genetic basis behind the adaptations has stimulated a lot of interest. Yet, the studied adaptations are generally focused on antibiotic resistance and rarely on the adaptation to the environment given by the host, and the potential trade-offs hindering adaptations to each step of the infection are rarely considered. Those trade-offs are key to understanding intrahost evolution and thus the dynamics of the infection. However, understanding these trade-offs supposes a detailed study of host-pathogen interactions at each step of the infection process, with an adapted methodology for each step. Using Drosophila melanogaster as the host and the bacterium Xenorhabdus nematophila, we investigated the bacterial adaptations resulting from GASP mutations known to induce the small colony variant (SCV) phenotype positively selected within the host over the course of an infection, as well as the trade-off between step-specific adaptations.
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Affiliation(s)
- Christian Faucher
- CNRS, UMR5174 EDB (Laboratoire Évolution & Diversité Biologique), Université Toulouse 3 Paul Sabatier, Toulouse, France
| | - Vincent Mazana
- CNRS, UMR5174 EDB (Laboratoire Évolution & Diversité Biologique), Université Toulouse 3 Paul Sabatier, Toulouse, France
| | - Marion Kardacz
- CNRS, UMR5174 EDB (Laboratoire Évolution & Diversité Biologique), Université Toulouse 3 Paul Sabatier, Toulouse, France
| | - Nathalie Parthuisot
- CNRS, UMR5174 EDB (Laboratoire Évolution & Diversité Biologique), Université Toulouse 3 Paul Sabatier, Toulouse, France
| | - Jean-Baptiste Ferdy
- CNRS, UMR5174 EDB (Laboratoire Évolution & Diversité Biologique), Université Toulouse 3 Paul Sabatier, Toulouse, France
| | - David Duneau
- CNRS, UMR5174 EDB (Laboratoire Évolution & Diversité Biologique), Université Toulouse 3 Paul Sabatier, Toulouse, France
- Instituto Gulbenkian de Ciência, Oeiras, Portugal
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8
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Cao M, Goodrich-Blair H. Xenorhabdus nematophila bacteria shift from mutualistic to virulent Lrp-dependent phenotypes within the receptacles of Steinernema carpocapsae insect-infective stage nematodes. Environ Microbiol 2020; 22:5433-5449. [PMID: 33078552 DOI: 10.1111/1462-2920.15286] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 10/03/2020] [Accepted: 10/18/2020] [Indexed: 01/06/2023]
Abstract
Xenorhabdus nematophila bacteria are mutualists of Steinernema carpocapsae nematodes and pathogens of insects. Xenorhabdus nematophila exhibits phenotypic variation between insect virulence (V) and the mutualistic (M) support of nematode reproduction and colonization initiation in the infective juvenile (IJ) stage nematode that carries X. nematophila between insect hosts. The V and M phenotypes occur reciprocally depending on levels of the transcription factor Lrp: high-Lrp expressors are M+V- while low-Lrp expressors are V+M-. We report here that variable (wild type) or fixed high-Lrp expressors also are optimized, relative to low- or no-Lrp expressors, for colonization of additional nematode stages: juvenile, adult and pre-transmission infective juvenile (IJ). In contrast, we found that after the bacterial population had undergone outgrowth in mature IJs, the advantage for colonization shifted to low-Lrp expressors: fixed low-Lrp expressors (M-V+) and wild type (M+V+) exhibited higher average bacterial CFU per IJ than did high-Lrp (M+V-) or no-Lrp (M-V-) strains. Further, the bacterial population becomes increasingly low-Lrp expressing, based on expression of an Lrp-dependent fluorescent reporter, as IJs age. These data support a model that virulent X. nematophila have a selective advantage and accumulate in aging IJs in advance of exposure to insect hosts in which this phenotype is necessary.
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Affiliation(s)
- Mengyi Cao
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Heidi Goodrich-Blair
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, 53706, USA.,Department of Microbiology, University of Tennessee, Knoxville, TN, 37996, USA
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9
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Martínez-Guitián M, Vázquez-Ucha JC, Álvarez-Fraga L, Conde-Pérez K, Vallejo JA, Perina A, Bou G, Poza M, Beceiro A. Global Transcriptomic Analysis During Murine Pneumonia Infection Reveals New Virulence Factors in Acinetobacter baumannii. J Infect Dis 2020; 223:1356-1366. [DOI: 10.1093/infdis/jiaa522] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Accepted: 08/13/2020] [Indexed: 12/15/2022] Open
Abstract
Abstract
Background
Infections caused by multidrug-resistant pathogens such as Acinetobacter baumannii constitute a major health problem worldwide. In this study we present a global in vivo transcriptomic analysis of A. baumannii isolated from the lungs of mice with pneumonia infection.
Methods
Mice were infected with A. baumannii ATCC 17978 and AbH12O-A2 strains and the total bacterial RNA were analyzed by RNA sequencing. Lists of differentially expressed genes were obtained and 14 of them were selected for gene deletion and further analysis.
Results
Transcriptomic analysis revealed a specific gene expression profile in A. baumannii during lung infection with upregulation of genes involved in iron acquisition and host invasion. Mutant strains lacking feoA, mtnN, yfgC, basB, hisF, oatA, and bfnL showed a significant loss of virulence in murine pneumonia. A decrease in biofilm formation, adherence to human epithelial cells, and growth rate was observed in selected mutants.
Conclusions
This study provides an insight into A. baumannii gene expression profile during murine pneumonia infection. Data revealed that 7 in vivo upregulated genes were involved in virulence and could be considered new therapeutic targets.
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Affiliation(s)
- Marta Martínez-Guitián
- Servicio de Microbiología del Complejo Hospitalario Universitario, Instituto de Investigación Biomédica, Centro de Investigaciones Científicas Avanzadas, Universidad de A Coruña, A Coruña, Spain
| | - Juan C Vázquez-Ucha
- Servicio de Microbiología del Complejo Hospitalario Universitario, Instituto de Investigación Biomédica, Centro de Investigaciones Científicas Avanzadas, Universidad de A Coruña, A Coruña, Spain
| | - Laura Álvarez-Fraga
- Servicio de Microbiología del Complejo Hospitalario Universitario, Instituto de Investigación Biomédica, Centro de Investigaciones Científicas Avanzadas, Universidad de A Coruña, A Coruña, Spain
| | - Kelly Conde-Pérez
- Servicio de Microbiología del Complejo Hospitalario Universitario, Instituto de Investigación Biomédica, Centro de Investigaciones Científicas Avanzadas, Universidad de A Coruña, A Coruña, Spain
| | - Juan A Vallejo
- Servicio de Microbiología del Complejo Hospitalario Universitario, Instituto de Investigación Biomédica, Centro de Investigaciones Científicas Avanzadas, Universidad de A Coruña, A Coruña, Spain
| | | | - Germán Bou
- Servicio de Microbiología del Complejo Hospitalario Universitario, Instituto de Investigación Biomédica, Centro de Investigaciones Científicas Avanzadas, Universidad de A Coruña, A Coruña, Spain
| | - Margarita Poza
- Servicio de Microbiología del Complejo Hospitalario Universitario, Instituto de Investigación Biomédica, Centro de Investigaciones Científicas Avanzadas, Universidad de A Coruña, A Coruña, Spain
| | - Alejandro Beceiro
- Servicio de Microbiología del Complejo Hospitalario Universitario, Instituto de Investigación Biomédica, Centro de Investigaciones Científicas Avanzadas, Universidad de A Coruña, A Coruña, Spain
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10
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Cambon MC, Parthuisot N, Pagès S, Lanois A, Givaudan A, Ferdy JB. Selection of Bacterial Mutants in Late Infections: When Vector Transmission Trades Off against Growth Advantage in Stationary Phase. mBio 2019; 10:e01437-19. [PMID: 31594811 PMCID: PMC6786866 DOI: 10.1128/mbio.01437-19] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Accepted: 09/04/2019] [Indexed: 11/20/2022] Open
Abstract
Bacterial infections are often composed of cells with distinct phenotypes that can be produced by genetic or epigenetic mechanisms. This phenotypic heterogeneity has proved to be important in many pathogens, because it can alter both pathogenicity and transmission. We studied how and why it can emerge during infection in the bacterium Xenorhabdus nematophila, a pathogen that kills insects and multiplies in the cadaver before being transmitted by the soil nematode vector Steinernema carpocapsae We found that phenotypic variants cluster in three groups, one of which is composed of lrp defective mutants. These mutants, together with variants of another group, have in common that they maintain high survival during late stationary phase. This probably explains why they increase in frequency: variants of X. nematophila with a growth advantage in stationary phase (GASP) are under strong positive selection both in prolonged culture and in late infections. We also found that the within-host advantage of these variants seems to trade off against transmission by nematode vectors: the variants that reach the highest load in insects are those that are the least transmitted.IMPORTANCE Pathogens can evolve inside their host, and the importance of this mutation-fueled process is increasingly recognized. A disease outcome may indeed depend in part on pathogen adaptations that emerge during infection. It is therefore important to document these adaptations and the conditions that drive them. In our study, we took advantage of the possibility to monitor within-host evolution in the insect pathogen X. nematophila We demonstrated that selection occurring in aged infection favors lrp defective mutants, because these metabolic mutants benefit from a growth advantage in stationary phase (GASP). We also demonstrated that these mutants have reduced virulence and impaired transmission, modifying the infection outcome. Beyond the specific case of X. nematophila, we propose that metabolic mutants are to be found in other bacterial pathogens that stay for many generations inside their host.
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Affiliation(s)
- Marine C Cambon
- Évolution et Diversité Biologique, CNRS-Université Paul Sabatier, Toulouse, France
- Diversité, Génome et Interactions Microorganismes Insectes, INRA-Université Montpellier, Montpellier, France
| | - Nathalie Parthuisot
- Évolution et Diversité Biologique, CNRS-Université Paul Sabatier, Toulouse, France
| | - Sylvie Pagès
- Diversité, Génome et Interactions Microorganismes Insectes, INRA-Université Montpellier, Montpellier, France
| | - Anne Lanois
- Diversité, Génome et Interactions Microorganismes Insectes, INRA-Université Montpellier, Montpellier, France
| | - Alain Givaudan
- Diversité, Génome et Interactions Microorganismes Insectes, INRA-Université Montpellier, Montpellier, France
| | - Jean-Baptiste Ferdy
- Évolution et Diversité Biologique, CNRS-Université Paul Sabatier, Toulouse, France
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11
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Hasan MA, Ahmed S, Mollah MMI, Lee D, Kim Y. Variation in pathogenicity of different strains of Xenorhabdus nematophila; Differential immunosuppressive activities and secondary metabolite production. J Invertebr Pathol 2019; 166:107221. [PMID: 31356819 DOI: 10.1016/j.jip.2019.107221] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Revised: 07/24/2019] [Accepted: 07/25/2019] [Indexed: 10/26/2022]
Abstract
Xenorhabdus nematophila, an entomopathogenic bacterium, is mutualistic with the nematode Steinernema carpocapsae. The bacterium produces secondary metabolites to inhibit target insect phospholipase A2 (PLA2) and induce immunosuppression, which is required for the pathogenicity of this bacterium-nematode complex. However, it was unclear if immunosuppressive intensity of the bacteria was correlated with their insecticidal potency. We compared six different X. nematophila strains inhibiting the immune responses of the beet armyworm (Spodoptera exigua) to explain their virulence variations. In addition to four known strains obtained from the Korean Agricultural Culture Collection, we identified two new strains (SK1 and SK2) of X. nematophila from two different isolates of S. carpocapsae. Although all six strains were virulent, they showed significant variation in median lethal bacterial dosage (LD50). The LD50 of most strains was 15-30 CFU/larva, however, the LD50 of the SK1 strain was more than two-fold higher against S. exigua larvae. Immunosuppressive activities of the six strains were measured by comparing hemocyte-spreading behavior and nodule formation; the SK1 strain was significantly less potent than other bacterial strains. These suppressed hemocyte behaviors were recovered by adding arachidonic acid (a catalytic product of PLA2) into all six strains. Bacterial culture broth was fractionated with different organic solvents and the ability to inhibit immune response and PLA2 activity were assessed. All organic extracts had immunosuppressive activities and PLA2-inhibitory activities. GC-MS analysis showed that these organic extracts possessed a total of 87 different compounds. There were variations in chemical components among the six bacterial strains. Organic extracts of SK1 strain, which exhibited the lowest virulence, contained the least number of secondary metabolites.
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Affiliation(s)
- Md Ariful Hasan
- Department of Plant Medicals, Andong National University, Andong 36729, Republic of Korea
| | - Shabbir Ahmed
- Department of Plant Medicals, Andong National University, Andong 36729, Republic of Korea
| | - Md Mahi Imam Mollah
- Department of Plant Medicals, Andong National University, Andong 36729, Republic of Korea
| | - Dongwoon Lee
- School of Environmental Ecology and Tourism, Kyungpook National University, Sangju 37224, Republic of Korea
| | - Yonggyun Kim
- Department of Plant Medicals, Andong National University, Andong 36729, Republic of Korea.
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12
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Kroner GM, Wolfe MB, Freddolino PL. Escherichia coli Lrp Regulates One-Third of the Genome via Direct, Cooperative, and Indirect Routes. J Bacteriol 2019; 201:e00411-18. [PMID: 30420454 PMCID: PMC6349092 DOI: 10.1128/jb.00411-18] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2018] [Accepted: 11/07/2018] [Indexed: 12/13/2022] Open
Abstract
The global regulator Lrp plays a crucial role in regulating metabolism, virulence, and motility in response to environmental conditions. Lrp has previously been shown to activate or repress approximately 10% of the genes in Escherichia coli However, the full spectrum of targets, and how Lrp acts to regulate them, have stymied earlier study. We have combined matched chromatin-immunoprecipitation sequencing (ChIP-seq) and RNA sequencing (RNA-seq) under nine physiological conditions to comprehensively map the binding and regulatory activity of Lrp as it directs responses to nutrient abundance. In addition to identifying hundreds of novel Lrp targets, we observe two new global trends, as follows: first, that Lrp will often bind to promoters in a poised position under conditions when it has no regulatory activity to enable combinatorial interactions with other regulators, and second, that nutrient levels induce a global shift in the equilibrium between less-sequence-specific and more-sequence-specific DNA binding. The overall regulatory behavior of Lrp, which as we now show extends to 38% of E. coli genes directly or indirectly under at least one condition, thus arises from the interaction between changes in Lrp binding specificity and cooperative action with other regulators.IMPORTANCE To survive, bacteria such as E. coli must rapidly respond to changing environmental conditions, including nutrient levels. A decrease in nutrient availability causes bacteria to stop rapid replication and enter stationary phase, where they perform limited to no cell division. The E. coli global regulatory protein Lrp has been previously implicated in modulating the expression of genes particularly important at this transition from rapid to slowed growth. Here, we monitor Lrp's DNA binding locations and effect on gene expression under three different nutrient conditions across three growth stages. We find that Lrp's role is even broader than previously suspected and that it appears to interact with many other bacterial regulators to perform its function in a condition-specific manner.
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Affiliation(s)
- Grace M Kroner
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan, USA
- Cellular Biotechnology Training Program, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Michael B Wolfe
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan, USA
- Department of Computational Medicine & Bioinformatics, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Peter L Freddolino
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan, USA
- Department of Computational Medicine & Bioinformatics, University of Michigan Medical School, Ann Arbor, Michigan, USA
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13
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Dreyer J, Malan AP, Dicks LMT. Bacteria of the Genus Xenorhabdus, a Novel Source of Bioactive Compounds. Front Microbiol 2018; 9:3177. [PMID: 30619229 PMCID: PMC6305712 DOI: 10.3389/fmicb.2018.03177] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Accepted: 12/07/2018] [Indexed: 12/04/2022] Open
Abstract
The genus Xenorhabdus of the family Enterobacteriaceae, are mutualistically associated with entomopathogenic nematodes of the genus Steinernema. Although most of the associations are species-specific, a specific Xenorhabdus sp. may infect more than one Steinernema sp. During the Xenorhabdus-Steinernema life cycle, insect larvae are infected and killed, while both mutualists produce bioactive compounds. These compounds act synergistically to ensure reproduction and proliferation of the nematodes and bacteria. A single strain of Xenorhabdus may produce a variety of antibacterial and antifungal compounds, some of which are also active against insects, nematodes, protozoa, and cancer cells. Antimicrobial compounds produced by Xenorhabdus spp. have not been researched to the same extent as other soil bacteria and they may hold the answer to novel antibacterial and antifungal compounds. This review summarizes the bioactive secondary metabolites produced by Xenorhabdus spp. and their application in disease control. Gene regulation and increasing the production of a few of these antimicrobial compounds are discussed. Aspects limiting future development of these novel bioactive compounds are also pointed out.
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Affiliation(s)
- Jönike Dreyer
- Department of Microbiology, Stellenbosch University, Stellenbosch, South Africa
| | - Antoinette P. Malan
- Department of Conservation Ecology and Entomology, Stellenbosch University, Stellenbosch, South Africa
| | - Leon M. T. Dicks
- Department of Microbiology, Stellenbosch University, Stellenbosch, South Africa
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14
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Zhang S, Fang X, Tang Q, Ge J, Wang Y, Zhang X. CpxR negatively regulates the production of xenocoumacin 1, a dihydroisocoumarin derivative produced by Xenorhabdus nematophila. Microbiologyopen 2018; 8:e00674. [PMID: 29888873 PMCID: PMC6391269 DOI: 10.1002/mbo3.674] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Revised: 05/07/2018] [Accepted: 05/19/2018] [Indexed: 11/10/2022] Open
Abstract
Xenocoumacin 1 (Xcn1), a major antimicrobial compound produced by Xenorhabdus nematophila, has great potential for use in agricultural productions. In this study, we evaluated the effects of CpxR, a global response regulator associated with the mutualism and pathogenesis of X. nematophila, on the antimicrobial activity and Xcn1 production. The mutation of cpxR could promote the production of Xcn1 significantly with its level in ΔcpxR mutant being 3.07 times higher than that in the wild type. Additionally, the expression levels of xcnA‐L genes, which are responsible for the production of Xcn1, were increased in ΔcpxR mutant while the expression levels of xcnMN, which are required for the conversion of Xcn1 into Xcn2 was reduced. Noticeably, Xcn2 was also enhanced on account of the conversion of excessive Xcn1 in spite of low expression levels of xcnM and xcnN in ΔcpxR mutant. The transcriptional levels of ompR and lrp, encoding the global response regulators OmpR and Lrp which negatively and positively regulate the production of Xcn1 were concurrently decreased and increased, respectively. Correspondingly, ΔcpxR mutant also exhibited increased antimicrobial activities in vitro and in vivo. Together, these findings suggest that CpxR negatively regulates xcnA‐L genes expression while positively regulating xcnMN expression in X. nematophila YL001, which led to a high yield of Xcn1 in ΔcpxR mutant.
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Affiliation(s)
- Shujing Zhang
- Research and Development Center of Biorational Pesticides, Key Laboratory of Plant Protection Resources and Pest Management of Ministry of Education, Northwest A &F University, Yangling, Shaanxi, China
| | - Xiangling Fang
- State Key Laboratory of Grassland Agro-ecosystems, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou, China.,School of Agriculture and Environment, Faculty of Science, The University of Western Australia, Crawley, Western Australia, Australia
| | - Qian Tang
- Research and Development Center of Biorational Pesticides, Key Laboratory of Plant Protection Resources and Pest Management of Ministry of Education, Northwest A &F University, Yangling, Shaanxi, China
| | - Jing Ge
- Research and Development Center of Biorational Pesticides, Key Laboratory of Plant Protection Resources and Pest Management of Ministry of Education, Northwest A &F University, Yangling, Shaanxi, China
| | - Yonghong Wang
- Research and Development Center of Biorational Pesticides, Key Laboratory of Plant Protection Resources and Pest Management of Ministry of Education, Northwest A &F University, Yangling, Shaanxi, China
| | - Xing Zhang
- Research and Development Center of Biorational Pesticides, Key Laboratory of Plant Protection Resources and Pest Management of Ministry of Education, Northwest A &F University, Yangling, Shaanxi, China
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15
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Yadav S, Gupta S, Eleftherianos I. Differential Regulation of Immune Signaling and Survival Response in Drosophila melanogaster Larvae upon Steinernema carpocapsae Nematode Infection. INSECTS 2018; 9:insects9010017. [PMID: 29419764 PMCID: PMC5872282 DOI: 10.3390/insects9010017] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/09/2017] [Revised: 01/27/2018] [Accepted: 02/01/2018] [Indexed: 01/11/2023]
Abstract
Drosophila melanogaster is an excellent model to dissect the molecular components and pathways of the innate anti-pathogen immune response. The nematode parasite Steinernema carpocapsae and its mutualistic bacterium Xenorhabdus nematophila form a complex that is highly pathogenic to insects, including D. melanogaster. We have used symbiotic (carrying X. nematophila) and axenic (lacking X. nematophila) nematodes to probe the regulation of genes belonging to different immune signaling pathways in D. melanogaster larvae and assess the survival response of certain mutants to these pathogens. We found that both types of S. carpocapsae upregulate MyD88 (Toll), but not PGRP-LE (Imd); whereas axenic S. carpocapsae strongly upregulate Wengen (Jnk), Domeless (Jak/Stat), Dawdle (TGFβ, Activin), and Decapentaplegic (TGFβ, BMP). We further found that inactivation of Wengen and Decapentaplegic confers a survival advantage to larvae infected with axenic S. carpocapsae, whereas mutating PGRP-LE promotes the survival of larvae infected with symbiotic nematodes.
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Affiliation(s)
- Shruti Yadav
- Insect Infection and Immunity Lab., Department of Biological Sciences, The George Washington University, Washington, DC 20052, USA.
| | - Sonali Gupta
- Insect Infection and Immunity Lab., Department of Biological Sciences, The George Washington University, Washington, DC 20052, USA.
| | - Ioannis Eleftherianos
- Insect Infection and Immunity Lab., Department of Biological Sciences, The George Washington University, Washington, DC 20052, USA.
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16
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Stilwell MD, Cao M, Goodrich-Blair H, Weibel DB. Studying the Symbiotic Bacterium Xenorhabdus nematophila in Individual, Living Steinernema carpocapsae Nematodes Using Microfluidic Systems. mSphere 2018; 3:e00530-17. [PMID: 29299529 PMCID: PMC5750387 DOI: 10.1128/msphere.00530-17] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Accepted: 11/29/2017] [Indexed: 01/01/2023] Open
Abstract
Animal-microbe symbioses are ubiquitous in nature and scientifically important in diverse areas, including ecology, medicine, and agriculture. Steinernema nematodes and Xenorhabdus bacteria compose an established, successful model system for investigating microbial pathogenesis and mutualism. The bacterium Xenorhabdus nematophila is a species-specific mutualist of insect-infecting Steinernema carpocapsae nematodes. The bacterium colonizes a specialized intestinal pocket within the infective stage of the nematode, which transports the bacteria between insects that are killed and consumed by the pair for reproduction. Current understanding of the interaction between the infective-stage nematode and its bacterial colonizers is based largely on population-level, snapshot time point studies on these organisms. This limitation arises because investigating temporal dynamics of the bacterium within the nematode is impeded by the difficulty of isolating and maintaining individual living nematodes and tracking colonizing bacterial cells over time. To overcome this challenge, we developed a microfluidic system that enables us to spatially isolate and microscopically observe individual, living Steinernema nematodes and monitor the growth and development of the associated X. nematophila bacterial communities-starting from a single cell or a few cells-over weeks. Our data demonstrate, to our knowledge, the first direct, temporal, in vivo visual analysis of a symbiosis system and the application of this system to reveal continuous dynamics of the symbiont population in the living host animal. IMPORTANCE This paper describes an experimental system for directly investigating population dynamics of a symbiotic bacterium, Xenorhabdus nematophila, in its host-the infective stage of the entomopathogenic nematode Steinernema carpocapsae. Tracking individual and groups of bacteria in individual host nematodes over days and weeks yielded insight into dynamic growth and topology changes of symbiotic bacterial populations within infective juvenile nematodes. Our approach for studying symbioses between bacteria and nematodes provides a system to investigate long-term host-microbe interactions in individual nematodes and extrapolate the lessons learned to other bacterium-animal interactions.
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Affiliation(s)
- Matthew D. Stilwell
- Department of Biochemistry, University of Wisconsin—Madison, Madison, Wisconsin, USA
| | - Mengyi Cao
- Department of Bacteriology, University of Wisconsin—Madison, Madison, Wisconsin, USA
| | - Heidi Goodrich-Blair
- Department of Bacteriology, University of Wisconsin—Madison, Madison, Wisconsin, USA
- Department of Microbiology, University of Tennessee—Knoxville, Knoxville, Tennessee, USA
| | - Douglas B. Weibel
- Department of Biochemistry, University of Wisconsin—Madison, Madison, Wisconsin, USA
- Department of Biomedical Engineering, University of Wisconsin—Madison, Madison, Wisconsin, USA
- Department of Chemistry, University of Wisconsin—Madison, Madison, Wisconsin, USA
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17
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Ho YC, Hung FR, Weng CH, Li WT, Chuang TH, Liu TL, Lin CY, Lo CJ, Chen CL, Chen JW, Hashimoto M, Hor LI. Lrp, a global regulator, regulates the virulence of Vibrio vulnificus. J Biomed Sci 2017; 24:54. [PMID: 28800764 PMCID: PMC5554404 DOI: 10.1186/s12929-017-0361-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Accepted: 08/04/2017] [Indexed: 12/18/2022] Open
Abstract
Background An attenuated mutant (designated NY303) of Vibrio vulnificus, which causes serious wound infection and septicemia in humans, was isolated fortuitously from a clinical strain YJ016. This mutant was defective in cytotoxicity, migration on soft agar and virulence in the mouse. The purpose of this study was to map the mutation in this attenuated mutant and further explore how the gene thus identified is involved in virulence. Methods The whole genome sequence of mutant NY303 determined by next-generation sequencing was compared with that of strain YJ016 to map the mutations. By isolating and characterizing the specific gene-knockout mutants, the gene associated with the phenotype of mutant NY303 was identified. This gene encodes a global regulator, Lrp. A mutant, YH01, deficient in Lrp was isolated and examined in vitro, in vivo and ex vivo to find the affected virulence mechanisms. The target genes of Lrp were further identified by comparing the transcriptomes, which were determined by RNA-seq, of strain YJ016 and mutant YH01. The promoters bound by Lrp were identified by genome footprinting-sequencing, and those related with virulence were further examined by electrophoretic mobility shift assay. Results A mutation in lrp was shown to be associated with the reduced cytotoxicity, chemotaxis and virulence of mutant NY303. Mutant YH01 exhibited a phenotype resembling that of mutant NY303, and was defective in colonization in the mouse and growth in mouse serum, but not the antiphagocytosis ability. 596 and 95 genes were down- and up-regulated, respectively, in mutant YH01. Many of the genes involved in secretion of the MARTX cytotoxin, chemotaxis and iron-acquisition were down-regulated in mutant YH01. The lrp gene, which was shown to be negatively autoregulated, and 7 down-regulated virulence-associated genes were bound by Lrp in their promoters. A 14-bp consensus sequence, mkCrTTkwAyTsTG, putatively recognized by Lrp was identified in the promoters of these genes. Conclusions Lrp is a global regulator involved in regulation of cytotoxicity, chemotaxis and iron-acquisition in V. vulnificus. Down-regulation of many of the genes associated with these properties may be responsible, at least partly, for loss of virulence in mutant NY303. Electronic supplementary material The online version of this article (doi:10.1186/s12929-017-0361-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Yu-Chi Ho
- Department of Microbiology and Immunology, College of Medicine, Tainan, 70101, Taiwan
| | - Feng-Ru Hung
- Department of Microbiology and Immunology, College of Medicine, Tainan, 70101, Taiwan
| | - Chao-Hui Weng
- Department of Microbiology and Immunology, College of Medicine, Tainan, 70101, Taiwan
| | - Wei-Ting Li
- Department of Microbiology and Immunology, College of Medicine, Tainan, 70101, Taiwan
| | - Tzu-Hung Chuang
- Institute of Bioinformatics and Biosignal Transduction, National Cheng Kung University, Tainan, 70101, Taiwan
| | - Tsung-Lin Liu
- Institute of Bioinformatics and Biosignal Transduction, National Cheng Kung University, Tainan, 70101, Taiwan
| | - Ching-Yuan Lin
- Department of Physics and Graduate Institute of Biophysics, National Central University, Taoyuan, 32001, Taiwan
| | - Chien-Jung Lo
- Department of Physics and Graduate Institute of Biophysics, National Central University, Taoyuan, 32001, Taiwan
| | - Chun-Liang Chen
- Department of Microbiology and Immunology, College of Medicine, Tainan, 70101, Taiwan
| | - Jen-Wei Chen
- Department of Microbiology and Immunology, College of Medicine, Tainan, 70101, Taiwan.,Center of Infectious Disease and Signal Transduction, National Cheng Kung University, Tainan, 70101, Taiwan
| | - Masayuki Hashimoto
- Center of Infectious Disease and Signal Transduction, National Cheng Kung University, Tainan, 70101, Taiwan.,Department of Molecular Medicine, National Cheng Kung University, Tainan, 70101, Taiwan
| | - Lien-I Hor
- Department of Microbiology and Immunology, College of Medicine, Tainan, 70101, Taiwan. .,Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, 70101, Taiwan.
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18
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Cao M, Goodrich-Blair H. Ready or Not: Microbial Adaptive Responses in Dynamic Symbiosis Environments. J Bacteriol 2017; 199:e00883-16. [PMID: 28484049 PMCID: PMC5512229 DOI: 10.1128/jb.00883-16] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In mutually beneficial and pathogenic symbiotic associations, microbes must adapt to the host environment for optimal fitness. Both within an individual host and during transmission between hosts, microbes are exposed to temporal and spatial variation in environmental conditions. The phenomenon of phenotypic variation, in which different subpopulations of cells express distinctive and potentially adaptive characteristics, can contribute to microbial adaptation to a lifestyle that includes rapidly changing environments. The environments experienced by a symbiotic microbe during its life history can be erratic or predictable, and each can impact the evolution of adaptive responses. In particular, the predictability of a rhythmic or cyclical series of environments may promote the evolution of signal transduction cascades that allow preadaptive responses to environments that are likely to be encountered in the future, a phenomenon known as adaptive prediction. In this review, we summarize environmental variations known to occur in some well-studied models of symbiosis and how these may contribute to the evolution of microbial population heterogeneity and anticipatory behavior. We provide details about the symbiosis between Xenorhabdus bacteria and Steinernema nematodes as a model to investigate the concept of environmental adaptation and adaptive prediction in a microbial symbiosis.
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Affiliation(s)
- Mengyi Cao
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Heidi Goodrich-Blair
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Microbiology, University of Tennessee Knoxville, Knoxville, Tennessee, USA
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19
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High Levels of the Xenorhabdus nematophila Transcription Factor Lrp Promote Mutualism with the Steinernema carpocapsae Nematode Host. Appl Environ Microbiol 2017; 83:AEM.00276-17. [PMID: 28389546 DOI: 10.1128/aem.00276-17] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Accepted: 04/04/2017] [Indexed: 11/20/2022] Open
Abstract
Xenorhabdus nematophila bacteria are mutualistic symbionts of Steinernema carpocapsae nematodes and pathogens of insects. The X. nematophila global regulator Lrp controls the expression of many genes involved in both mutualism and pathogenic activities, suggesting a role in the transition between the two host organisms. We previously reported that natural populations of X. nematophila exhibit various levels of Lrp expression and that cells expressing relatively low levels of Lrp are optimized for virulence in the insect Manduca sexta The adaptive advantage of the high-Lrp-expressing state was not established. Here we used strains engineered to express constitutively high or low levels of Lrp to test the model in which high-Lrp-expressing cells are adapted for mutualistic activities with the nematode host. We demonstrate that high-Lrp cells form more robust biofilms in laboratory media than do low-Lrp cells, which may reflect adherence to host tissues. Also, our data showed that nematodes cultivated with high-Lrp strains are more frequently colonized than are those associated with low-Lrp strains. Taken together, these data support the idea that high-Lrp cells have an advantage in tissue adherence and colonization initiation. Furthermore, our data show that high-Lrp-expressing strains better support nematode reproduction than do their low-Lrp counterparts under both in vitro and in vivo conditions. Our data indicate that heterogeneity of Lrp expression in X. nematophila populations provides diverse cell populations adapted to both pathogenic (low-Lrp) and mutualistic (high-Lrp) states.IMPORTANCE Host-associated bacteria experience fluctuating conditions during both residence within an individual host and transmission between hosts. For bacteria that engage in evolutionarily stable, long-term relationships with particular hosts, these fluctuations provide selective pressure for the emergence of adaptive regulatory mechanisms. Here we present evidence that the bacterium Xenorhabdus nematophila uses various levels of the transcription factor Lrp to optimize its association with its two animal hosts, nematodes and insects, with which it behaves as a mutualist and a pathogen, respectively. Building on our previous finding that relatively low cellular levels of Lrp are optimal for pathogenesis, we demonstrate that, conversely, high levels of Lrp promote mutualistic activities with the Steinernema carpocapsae nematode host. These data suggest that X. nematophila has evolved to utilize phenotypic variation between high- and low-Lrp-expression states to optimize its alternating behaviors as a mutualist and a pathogen.
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20
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The Global Transcription Factor Lrp Is both Essential for and Inhibitory to Xenorhabdus nematophila Insecticidal Activity. Appl Environ Microbiol 2017; 83:AEM.00185-17. [PMID: 28411220 DOI: 10.1128/aem.00185-17] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Accepted: 04/06/2017] [Indexed: 01/04/2023] Open
Abstract
In the entomopathogenic bacterium Xenorhabdus nematophila, cell-to-cell variation in the abundance of the Lrp transcription factor leads to virulence modulation; low Lrp levels are associated with a virulent phenotype and suppression of antimicrobial peptides (AMPs) in Manduca sexta insects, while cells that lack lrp or express high Lrp levels are virulence attenuated and elicit AMP expression. To better understand the basis of these phenotypes, we examined X. nematophila strains expressing fixed Lrp levels. Unlike the lrp-null mutant, the high-lrp strain is fully virulent in Drosophila melanogaster, suggesting that these two strains have distinct underlying causes of virulence attenuation in M. sexta Indeed, the lrp-null mutant was defective in cytotoxicity against M. sexta hemocytes relative to that in the high-lrp and low-lrp strains. Further, supernatant derived from the lrp-null mutant but not from the high-lrp strain was defective in inhibiting weight gain when fed to 1st instar M. sexta These data suggest that contributors to the lrp-null mutant virulence attenuation phenotype are the lack of Lrp-dependent cytotoxic and extracellular oral growth inhibitory activities, which may be particularly important for virulence in D. melanogaster In contrast, the high-Lrp strain was sensitive to the antimicrobial peptide cecropin, had a transient survival defect in M. sexta, and had reduced extracellular levels of insecticidal activity, measured by injection of supernatant into 4th instar M. sexta Thus, high-lrp strain virulence attenuation may be explained by its hypersensitivity to M. sexta host immunity and its inability to secrete one or more insecticidal factors.IMPORTANCE Adaptation of a bacterial pathogen to host environments can be achieved through the coordinated regulation of virulence factors that can optimize success under prevailing conditions. In the insect pathogen Xenorhabdus nematophila, the global transcription factor Lrp is necessary for virulence when injected into Manduca sexta or Drosophila melanogaster insect hosts. However, high levels of Lrp, either naturally occurring or artificially induced, cause attenuation of X. nematophila virulence in M. sexta but not D. melanogaster Here, we present evidence suggesting that the underlying cause of high-Lrp-dependent virulence attenuation in M. sexta is hypersensitivity to host immune responses and decreased insecticidal activity and that high-Lrp virulence phenotypes are insect host specific. This knowledge suggests that X. nematophila faces varied challenges depending on the type of insect host it infects and that its success in these environments depends on Lrp-dependent control of a multifactorial virulence repertoire.
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21
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Engel Y, Windhorst C, Lu X, Goodrich-Blair H, Bode HB. The Global Regulators Lrp, LeuO, and HexA Control Secondary Metabolism in Entomopathogenic Bacteria. Front Microbiol 2017; 8:209. [PMID: 28261170 PMCID: PMC5313471 DOI: 10.3389/fmicb.2017.00209] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Accepted: 01/30/2017] [Indexed: 11/13/2022] Open
Abstract
Photorhabdus luminescens TTO1 and Xenorhabdus nematophila HGB081 are insect pathogenic bacteria and producers of various structurally diverse bioactive natural products. In these entomopathogenic bacteria we investigated the role of the global regulators Lrp, LeuO, and HexA in the production of natural products. Lrp is a general activator of natural product biosynthesis in X. nematophila and for most compounds in TTO1. Microarray analysis confirmed these results in X. nematophila and enabled the identification of additional biosynthesis gene clusters (BGC) regulated by Lrp. Moreover, when promoters of two X. nematophila BGC were analyzed, transcriptional activation by Lrp was observed. In contrast, LeuO in X. nematophila and P. luminescens has both repressing and activating features, depending on the natural product examined. Furthermore, heterologous overexpression of leuO from X. nematophila in the closely related Xenorhabdus szentirmaii resulted in overproduction of several natural products including novel compounds. The presented findings could be of importance for establishing a tool for overproduction of secondary metabolites and subsequent identification of novel compounds.
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Affiliation(s)
- Yvonne Engel
- Merck-Stiftungsprofessur Molekulare Biotechnologie, Molekulare Biowissenschaften, Goethe Universität Frankfurt Frankfurt am Main, Germany
| | - Carina Windhorst
- Merck-Stiftungsprofessur Molekulare Biotechnologie, Molekulare Biowissenschaften, Goethe Universität Frankfurt Frankfurt am Main, Germany
| | - Xiaojun Lu
- Department of Bacteriology, University of Wisconsin-Madison, Madison WI, USA
| | - Heidi Goodrich-Blair
- Department of Bacteriology, University of Wisconsin-Madison, MadisonWI, USA; Department of Microbiology, University of Tennessee, Knoxville, KnoxvilleTN, USA
| | - Helge B Bode
- Merck-Stiftungsprofessur Molekulare Biotechnologie, Molekulare Biowissenschaften, Goethe Universität FrankfurtFrankfurt am Main, Germany; Buchmann Institute for Molecular Life Sciences (BMLS), Goethe Universität FrankfurtFrankfurt am Main, Germany
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Unoarumhi Y, Blumenthal RM, Matson JS. Evolution of a global regulator: Lrp in four orders of γ-Proteobacteria. BMC Evol Biol 2016; 16:111. [PMID: 27206730 PMCID: PMC4875751 DOI: 10.1186/s12862-016-0685-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Accepted: 05/12/2016] [Indexed: 11/11/2022] Open
Abstract
Background Bacterial global regulators each regulate the expression of several hundred genes. In Escherichia coli, the top seven global regulators together control over half of all genes. Leucine-responsive regulatory protein (Lrp) is one of these top seven global regulators. Lrp orthologs are very widely distributed, among both Bacteria and Archaea. Surprisingly, even within the phylum γ-Proteobacteria (which includes E. coli), Lrp is a global regulator in some orders and a local regulator in others. This raises questions about the evolution of Lrp and, more broadly, of global regulators. Results We examined Lrp sequences from four bacterial orders of the γ-Proteobacteria using phylogenetic and Logo analyses. The orders studied were Enterobacteriales and Vibrionales, in which Lrp plays a global role in tested species; Pasteurellales, in which Lrp is a local regulator in the tested species; and Alteromonadales, an order closely related to the other three but in which Lrp has not yet been studied. For comparison, we analyzed the Lrp paralog AsnC, which in all tested cases is a local regulator. The Lrp and AsnC phylogenetic clusters each divided, as expected, into subclusters representing the Enterobacteriales, Vibrionales, and Pasteuralles. However the Alteromonadales did not yield coherent clusters for either Lrp or AsnC. Logo analysis revealed signatures associated with globally- vs. locally- acting Lrp orthologs, providing testable hypotheses for which portions of Lrp are responsible for a global vs. local role. These candidate regions include both ends of the Lrp polypeptide but not, interestingly, the highly-conserved helix-turn-helix motif responsible for DNA sequence specificity. Conclusions Lrp and AsnC have conserved sequence signatures that allow their unambiguous annotation, at least in γ-Proteobacteria. Among Lrp orthologs, specific residues correlated with global vs. local regulatory roles, and can now be tested to determine which are functionally relevant and which simply reflect divergence. In the Alteromonadales, it appears that there are different subgroups of Lrp orthologs, one of which may act globally while the other may act locally. These results suggest experiments to improve our understanding of the evolution of bacterial global regulators. Electronic supplementary material The online version of this article (doi:10.1186/s12862-016-0685-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Yvette Unoarumhi
- Department of Medical Microbiology and Immunology, University of Toledo College of Medicine and Life Sciences, Toledo, Ohio, USA.,Program in Bioinformatics and Proteomics/Genomics, University of Toledo College of Medicine and Life Sciences, Toledo, OH, USA
| | - Robert M Blumenthal
- Department of Medical Microbiology and Immunology, University of Toledo College of Medicine and Life Sciences, Toledo, Ohio, USA.,Program in Bioinformatics and Proteomics/Genomics, University of Toledo College of Medicine and Life Sciences, Toledo, OH, USA
| | - Jyl S Matson
- Department of Medical Microbiology and Immunology, University of Toledo College of Medicine and Life Sciences, Toledo, Ohio, USA.
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