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Dessartine MM, Kosta A, Doan T, Cascales É, Côté JP. Type 1 fimbriae-mediated collective protection against type 6 secretion system attacks. mBio 2024; 15:e0255323. [PMID: 38497656 PMCID: PMC11005336 DOI: 10.1128/mbio.02553-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Accepted: 01/25/2024] [Indexed: 03/19/2024] Open
Abstract
Bacterial competition may rely on secretion systems such as the type 6 secretion system (T6SS), which punctures and releases toxic molecules into neighboring cells. To subsist, bacterial targets must counteract the threats posed by T6SS-positive competitors. In this study, we used a comprehensive genome-wide high-throughput screening approach to investigate the dynamics of interbacterial competition. Our primary goal was to identify deletion mutants within the well-characterized E. coli K-12 single-gene deletion library, the Keio collection, that demonstrated resistance to T6SS-mediated killing by the enteropathogenic bacterium Cronobacter malonaticus. We identified 49 potential mutants conferring resistance to T6SS and focused our interest on a deletion mutant (∆fimE) exhibiting enhanced expression of type 1 fimbriae. We demonstrated that the presence of type 1 fimbriae leads to the formation of microcolonies and thus protects against T6SS-mediated assaults. Collectively, our study demonstrated that adhesive structures such as type 1 fimbriae confer collective protective behavior against T6SS attacks.IMPORTANCEType 6 secretion systems (T6SS) are molecular weapons employed by gram-negative bacteria to eliminate neighboring microbes. T6SS plays a pivotal role as a virulence factor, enabling pathogenic gram-negative bacteria to compete with the established communities to colonize hosts and induce infections. Gaining a deeper understanding of bacterial interactions will allow the development of strategies to control the action of systems such as the T6SS that can manipulate bacterial communities. In this context, we demonstrate that bacteria targeted by T6SS attacks from the enteric pathogen Cronobacter malonaticus, which poses a significant threat to infants, can develop a collective protective mechanism centered on the production of type I fimbriae. These adhesive structures promote the aggregation of bacterial preys and the formation of microcolonies, which protect the cells from T6SS attacks.
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Affiliation(s)
- Margot Marie Dessartine
- Département de biologie, Faculté des sciences, Université de Sherbrooke, Sherbrooke, Quebec, Canada
| | - Artemis Kosta
- Plateforme de microscopie, Institut de Microbiologie de la Méditerranée (IMM, FR3479), Aix-Marseille Univ, CNRS, Marseille, France
| | - Thierry Doan
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM, UMR7255), Institut de Microbiologie de la Méditerranée, Aix Marseille Univ, CNRS, Marseille, France
| | - Éric Cascales
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM, UMR7255), Institut de Microbiologie de la Méditerranée, Aix Marseille Univ, CNRS, Marseille, France
| | - Jean-Philippe Côté
- Département de biologie, Faculté des sciences, Université de Sherbrooke, Sherbrooke, Quebec, Canada
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2
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Cordero M, Mitarai N, Jauffred L. Motility mediates satellite formation in confined biofilms. ISME J 2023; 17:1819-1827. [PMID: 37592064 PMCID: PMC10579341 DOI: 10.1038/s41396-023-01494-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Revised: 08/07/2023] [Accepted: 08/08/2023] [Indexed: 08/19/2023]
Abstract
Bacteria have spectacular survival capabilities and can spread in many, vastly different environments. For instance, when pathogenic bacteria infect a host, they expand by proliferation and squeezing through narrow pores and elastic matrices. However, the exact role of surface structures-important for biofilm formation and motility-and matrix density in colony expansion and morphogenesis is still largely unknown. Using confocal laser-scanning microscopy, we show how satellite colonies emerge around Escherichia coli colonies embedded in semi-dense hydrogel in controlled in vitro assays. Using knock-out mutants, we tested how extra-cellular structures, (e.g., exo-polysaccharides, flagella, and fimbria) control this morphology. Moreover, we identify the extra-cellular matrix' density, where this morphology is possible. When paralleled with mathematical modelling, our results suggest that satellite formation allows bacterial communities to spread faster. We anticipate that this strategy is important to speed up expansion in various environments, while retaining the close interactions and protection provided by the community.
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Affiliation(s)
- Mireia Cordero
- The Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, DK-2100, Copenhagen O, Denmark
| | - Namiko Mitarai
- The Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, DK-2100, Copenhagen O, Denmark.
| | - Liselotte Jauffred
- The Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, DK-2100, Copenhagen O, Denmark.
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3
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Tambassi M, Passarini E, Menozzi I, Berni M, Bracchi C, Dodi A, Bolzoni L, Scaltriti E, Morganti M, Ferrarini G, Sordi L, Sarti M, Ambretti S, Pongolini S. Klebsiella pneumoniae carrying multiple alleles of antigen 43-encoding gene of Escherichia coli associated with biofilm formation. Eur J Clin Microbiol Infect Dis 2023; 42:371-7. [PMID: 36695920 DOI: 10.1007/s10096-023-04552-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Accepted: 01/14/2023] [Indexed: 01/26/2023]
Abstract
A clinical strain of Klebsiella pneumoniae typed as sequence type 307 carrying three different alleles of the flu gene encoding the Escherichia coli virulence factor antigen 43 associated with biofilm formation was detected and characterized. The flu alleles are located in the chromosome inside putative integrative conjugative elements. The strain displays the phenotypes associated with Ag43, i.e. bi-phasic colony morphology and enhanced biofilm production. Furthermore, the strain produces low amount of capsule known to affect Ag43 function. Analysis of 1431 worldwide deposited genomes revealed that 3.7% Klebsiella pneumoniae carry one or two flu alleles.
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4
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Puri D, Fang X, Allison KR. Evidence of a possible multicellular life cycle in Escherichia coli. iScience 2022; 26:105795. [PMID: 36594031 PMCID: PMC9804144 DOI: 10.1016/j.isci.2022.105795] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Revised: 10/07/2022] [Accepted: 12/08/2022] [Indexed: 12/14/2022] Open
Abstract
Biofilms are surface-attached multicellular microbial communities. Their genetics have been extensively studied, but the cell-scale morphogenetic events of their formation are largely unknown. Here, we recorded the entirety of morphogenesis in Escherichia coli, and discovered a previously unknown multicellular self-assembly process. Unattached, single-cells formed 4-cell rosettes which grew into constant-width chains. After ∼10 cell generations, these multicellular chains attached to surfaces and stopped growing. Chains remained clonal throughout morphogenesis. We showed that this process generates biofilms, which we found are composed of attached clonal chains, aligned in parallel. We investigated genetics of chain morphogenesis: Ag43 facilitates rosette formation and clonality; type-1 fimbriae and curli promote stability and configuration; and extracellular polysaccharide production facilitates attachment. Our study establishes that E. coli, a unicellular organism, can follow a multistage, clonal, genetically-regulated, rosette-initiated multicellular life cycle. These findings have implications for synthetic biology, multicellular development, and the treatment and prevention of bacterial diseases.
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Affiliation(s)
- Devina Puri
- Wallace H. Coulter Department of Biomedical Engineering, Emory University and Georgia Institute of Technology, Atlanta, GA, USA
| | - Xin Fang
- Wallace H. Coulter Department of Biomedical Engineering, Emory University and Georgia Institute of Technology, Atlanta, GA, USA
| | - Kyle R. Allison
- Wallace H. Coulter Department of Biomedical Engineering, Emory University and Georgia Institute of Technology, Atlanta, GA, USA,Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, GA, USA,Corresponding author
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5
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Koonjan S, Cardoso Palacios C, Nilsson AS. Population Dynamics of a Two Phages–One Host Infection System Using Escherichia coli Strain ECOR57 and Phages vB_EcoP_SU10 and vB_EcoD_SU57. Pharmaceuticals (Basel) 2022; 15:ph15030268. [PMID: 35337066 PMCID: PMC8953519 DOI: 10.3390/ph15030268] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 02/09/2022] [Accepted: 02/18/2022] [Indexed: 02/01/2023] Open
Abstract
In this study, we looked at the population dynamics of a two phages-one host system using phages vB_EcoP_SU10 (SU10) and vB_EcoD_SU57 (SU57) and the bacteria Escherichia coli, strain ECOR57. Phage-specific growth curves were observed where infections by SU10 resulted in a moderate production of phages and infections by SU57 resulted in a fast and extensive production of phage progeny. Sequentially adding SU10 followed by SU57 did not produce a significant change in growth rates, whereas adding SU57 followed by SU10 resulted in a decrease in SU10 titer The efficiency of the plating assays showed that ECOR57 exhibited a resistance spectrum after infection by both the single and combined phages. Phage-resistant bacteria exhibited four different morphotypes (i.e., normal, slimy, edgy, and pointy). The normal and edgy morphotypes had a high frequency of developing resistance. Bacterial growth and biofilm assays indicated that the edgy and pointy morphotypes reached a stationary phase faster and produced more biofilm compared to the wild type. These findings suggest that the dynamic structure of phage–bacteria communities dictate resistance evolution and development. Understanding when and how resistances arise and phage(s)–hosts interactions could aid in the design of phage therapy treatments.
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Affiliation(s)
- Shazeeda Koonjan
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, SE-106 91 Stockholm, Sweden;
- Correspondence: (S.K.); (A.S.N.)
| | - Carlos Cardoso Palacios
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, SE-106 91 Stockholm, Sweden;
- Department of Ecology, Grimsö Wildlife Research Station, Swedish University of Agricultural Sciences, SE-739 93 Riddarhyttan, Sweden
| | - Anders S. Nilsson
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, SE-106 91 Stockholm, Sweden;
- Correspondence: (S.K.); (A.S.N.)
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6
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Xue Z, Pang Y, Quan S. Revisiting the functions of periplasmic chaperones in the quality control of the autotransporter Ag43 using a phenotypically homogeneous Escherichia coli strain. Biochem Biophys Res Commun 2021; 591:37-43. [PMID: 34995984 DOI: 10.1016/j.bbrc.2021.12.110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Accepted: 12/28/2021] [Indexed: 11/02/2022]
Abstract
Antigen 43 is a surface-displayed autotransporter protein that mediates bacterial self-association and pathogenicity. The quality control factors that facilitate Ag43 crossing the periplasm and inserting into the outer membrane remain enigmatic, mostly because Ag43 is phase variable and associated with heterologous phenotypes, which obscures the mutational effects of potential quality control factors. Here, we describe a screening method that allowed us to isolate a subpopulation of Escherichia coli that consistently displays an Ag43-mediated autoaggregation phenotype. Based on this subpopulation, we analyzed how disruptions of known periplasmic chaperones affect Ag43 biogenesis. We found that only the disruption of surA reduced Ag43 levels and abolished the autoaggregation phenotype of cells, but surA disruption did not affect the phase-variable expression of agn43. Using purified proteins, we showed that SurA effectively protected the β-barrel domain of Ag43 from aggregation. In contrast, the previously reported Ag43 biogenesis factor OsmY showed weak chaperoning effects on Ag43 only in the absence of SurA. Our results shed light on the roles of different periplasmic chaperones in Ag43 biogenesis and provide a methodology applicable to the study of other phase-variable proteins.
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Affiliation(s)
- Zixiao Xue
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai Collaborative Innovation Center for Biomanufacturing (SCICB), Shanghai, 200237, China
| | - Yonghao Pang
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai Collaborative Innovation Center for Biomanufacturing (SCICB), Shanghai, 200237, China
| | - Shu Quan
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai Collaborative Innovation Center for Biomanufacturing (SCICB), Shanghai, 200237, China; Shanghai Frontiers Science Center of Optogenetic Techniques for Cell Metabolism, Shanghai, 200237, China.
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7
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Gregorchuk BSJ, Reimer SL, Green KAC, Cartwright NH, Beniac DR, Hiebert SL, Booth TF, Chong PM, Westmacott GR, Zhanel GG, Bay DC. Phenotypic and Multi-Omics Characterization of Escherichia coli K-12 Adapted to Chlorhexidine Identifies the Role of MlaA and Other Cell Envelope Alterations Regulated by Stress Inducible Pathways in CHX Resistance. Front Mol Biosci 2021; 8:659058. [PMID: 34095221 PMCID: PMC8170033 DOI: 10.3389/fmolb.2021.659058] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Accepted: 04/09/2021] [Indexed: 11/27/2022] Open
Abstract
Chlorhexidine (CHX) is an essential medicine used as a topical antiseptic in skin and oral healthcare treatments. The widespread use of CHX has increased concerns regarding the development of antiseptic resistance in Enterobacteria and its potential impact on cross-resistance to other antimicrobials. Similar to other cationic antiseptics, resistance to CHX is believed to be driven by three membrane-based mechanisms: lipid synthesis/transport, altered porin expression, and increased efflux pump activity; however, specific gene and protein alterations associated with CHX resistance remain unclear. Here, we adapted Escherichia coli K-12 BW25113 to increasing concentrations of CHX to determine what phenotypic, morphological, genomic, transcriptomic, and proteomic changes occurred. We found that CHX-adapted E. coli isolates possessed no cross-resistance to any other antimicrobials we tested. Scanning electron microscopy imaging revealed that CHX adaptation significantly altered mean cell widths and lengths. Proteomic analyses identified changes in the abundance of porin OmpF, lipid synthesis/transporter MlaA, and efflux pump MdfA. Proteomic and transcriptomic analyses identified that CHX adaptation altered E. coli transcripts and proteins controlling acid resistance (gadE, cdaR) and antimicrobial stress-inducible pathways Mar-Sox-Rob, stringent response systems. Whole genome sequencing analyses revealed that all CHX-resistant isolates had single nucleotide variants in the retrograde lipid transporter gene mlaA as well as the yghQ gene associated with lipid A transport and synthesis. CHX resistant phenotypes were reversible only when complemented with a functional copy of the mlaA gene. Our results highlight the importance of retrograde phospholipid transport and stress response systems in CHX resistance and the consequences of prolonged CHX exposure.
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Affiliation(s)
- Branden S J Gregorchuk
- Department of Medical Microbiology and Infectious Diseases, University of Manitoba, Winnipeg, MB, Canada
| | - Shelby L Reimer
- Department of Medical Microbiology and Infectious Diseases, University of Manitoba, Winnipeg, MB, Canada
| | - Kari A C Green
- Department of Medical Microbiology and Infectious Diseases, University of Manitoba, Winnipeg, MB, Canada
| | - Nicola H Cartwright
- Department of Medical Microbiology and Infectious Diseases, University of Manitoba, Winnipeg, MB, Canada
| | - Daniel R Beniac
- National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, MB, Canada
| | - Shannon L Hiebert
- National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, MB, Canada
| | - Timothy F Booth
- Department of Medical Microbiology and Infectious Diseases, University of Manitoba, Winnipeg, MB, Canada.,National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, MB, Canada
| | - Patrick M Chong
- National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, MB, Canada
| | - Garrett R Westmacott
- National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, MB, Canada
| | - George G Zhanel
- Department of Medical Microbiology and Infectious Diseases, University of Manitoba, Winnipeg, MB, Canada
| | - Denice C Bay
- Department of Medical Microbiology and Infectious Diseases, University of Manitoba, Winnipeg, MB, Canada
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8
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Abe CM, Matheus-Guimarães C, Garcia BG, Cabilio Guth BE. Interactions of Shiga toxin-producing Escherichia coli with leafy green vegetables. Braz J Microbiol 2020; 51:797-803. [PMID: 32125677 DOI: 10.1007/s42770-020-00251-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Accepted: 02/20/2020] [Indexed: 10/24/2022] Open
Abstract
Shiga toxin-producing Escherichia coli (STEC) are important foodborne pathogens responsible for a wide spectrum of diseases including diarrhea, bloody diarrhea, and hemolytic uremic syndrome (HUS). A considerable number of outbreaks and sporadic cases of HUS have been associated with ingestion of fresh ready-to-eat products. Maintenance and persistence of STEC in the environment and foods can be related to its ability to form biofilm. A non-O157 STEC strain isolated from bovine feces was distinguished by its great ability to form biofilm in abiotic surfaces. In the present study, we aimed to investigate the ability of this strain to adhere to rocket leaves (Eruca sativa). Adherence assays were carried out for 3 h at 28 °C and analyzed by scanning electron microscopy. The non-O157 STEC strain adhered to leaf surface and inside the stomata forming several bacterial aggregates. The number of adherent bacteria per square millimeter of leaf was eightfold higher compared with an O157 STEC strain. Deletion of the STEC autotransporter protein contributing to biofilm (Sab) reduced the adherence ability of the non-O157 strain in almost 50%, and deletion of antigen 43 (Ag43) almost abolished this interaction. Very few bacteria were seen on the leaf surface, and these differences were statistically significant, suggesting the role of both proteins and especially Ag43 in the interaction of the non-O157 STEC strain with leaves. The risk posed by non-O157 STEC adherence to leaves on fresh produce contamination should not be neglected, and measures that effectively control adherence should be included in strategies to control non-O157 STEC.
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9
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Mickalide H, Kuehn S. Higher-Order Interaction between Species Inhibits Bacterial Invasion of a Phototroph-Predator Microbial Community. Cell Syst 2019; 9:521-533.e10. [PMID: 31838145 DOI: 10.1016/j.cels.2019.11.004] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Revised: 07/26/2019] [Accepted: 11/07/2019] [Indexed: 12/15/2022]
Abstract
The composition of an ecosystem is thought to be important for determining its resistance to invasion. Studies of natural ecosystems, from plant to microbial communities, have found that more diverse communities are more resistant to invasion. In some cases, more diverse communities resist invasion by more completely consuming the resources necessary for the invader. We show that Escherichia coli can successfully invade cultures of the alga Chlamydomonas reinhardtii (phototroph) or the ciliate Tetrahymena thermophila (predator) but cannot invade a community where both are present. The invasion resistance of the algae-ciliate community arises from a higher-order interaction between species (interaction modification) that is unrelated to resource consumption. We show that the mode of this interaction is the algal inhibition of bacterial aggregation, which leaves bacteria vulnerable to predation. This mode requires both the algae and the ciliate to be present and provides an example of invasion resistance through an interaction modification.
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Matange N, Hegde S, Bodkhe S. Adaptation Through Lifestyle Switching Sculpts the Fitness Landscape of Evolving Populations: Implications for the Selection of Drug-Resistant Bacteria at Low Drug Pressures. Genetics 2019; 211:1029-44. [PMID: 30670539 DOI: 10.1534/genetics.119.301834] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Accepted: 01/16/2019] [Indexed: 12/21/2022] Open
Abstract
Novel genotypes evolve under selection through mutations in pre-existing genes. However, mutations have pleiotropic phenotypic effects that influence the fitness of emerging genotypes in complex ways. The evolution of antimicrobial resistance is mediated by selection of mutations in genes coding for antibiotic-target proteins. Drug-resistance is commonly associated with a fitness cost due to the impact of resistance-conferring mutations on protein function and/or stability. These costs are expected to prohibit the selection of drug-resistant mutations at low drug pressures. Using laboratory evolution of rifampicin resistance in Escherichia coli, we show that when exposed intermittently to low concentration (0.1 × minimal inhibitory concentration) of rifampicin, the evolution of canonical drug resistance was indeed unfavorable. Instead, these bacterial populations adapted by evolving into small-colony variants that displayed enhanced pellicle-forming ability. This shift in lifestyle from planktonic to pellicle-like was necessary for enhanced fitness at low drug pressures, and was mediated by the genetic activation of the fim operon promoter, which allowed expression of type I fimbriae. Upon continued low drug exposure, these bacteria evolved exclusively into high-level drug-resistant strains through mutations at a limited set of loci within the rifampicin-resistance determining region of the rpoB gene. We show that our results are explained by mutation-specific epistasis, resulting in differential impact of lifestyle switching on the competitive fitness of different rpoB mutations. Thus, lifestyle-alterations that are selected at low selection pressures have the potential to modify the fitness effects of mutations, change the genetic structure, and affect the ultimate fate of evolving populations.
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11
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Nakatani H, Kanie J, Hori K. On‐fiber display of a functional peptide at sites distant from the cell surface using a long bacterionanofiber of a trimeric autotransporter adhesin. Biotechnol Bioeng 2018; 116:239-249. [DOI: 10.1002/bit.26857] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Revised: 10/20/2018] [Accepted: 10/30/2018] [Indexed: 01/08/2023]
Affiliation(s)
- Hajime Nakatani
- Department of Biomolecular EngineeringGraduate School of Engineering, Nagoya University, Furo‐cho, Chikusa‐kuNagoya Japan
| | - Junichi Kanie
- Department of Biomolecular EngineeringGraduate School of Engineering, Nagoya University, Furo‐cho, Chikusa‐kuNagoya Japan
| | - Katsutoshi Hori
- Department of Biomolecular EngineeringGraduate School of Engineering, Nagoya University, Furo‐cho, Chikusa‐kuNagoya Japan
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12
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Watson C, Hush P, Williams J, Dawson A, Ojkic N, Titmuss S, Waclaw B. Reduced adhesion between cells and substrate confers selective advantage in bacterial colonies
(a). ACTA ACUST UNITED AC 2018. [DOI: 10.1209/0295-5075/123/68001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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13
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Abstract
Stochastic phenotype switching has been suggested to play a beneficial role in microbial populations by leading to the division of labour among cells, or ensuring that at least some of the population survives an unexpected change in environmental conditions. Here we use a computational model to investigate an alternative possible function of stochastic phenotype switching: as a way to adapt more quickly even in a static environment. We show that when a genetic mutation causes a population to become less fit, switching to an alternative phenotype with higher fitness (growth rate) may give the population enough time to develop compensatory mutations that increase the fitness again. The possibility of switching phenotypes can reduce the time to adaptation by orders of magnitude if the “fitness valley” caused by the deleterious mutation is deep enough. Our work has important implications for the emergence of antibiotic-resistant bacteria. In line with recent experimental findings, we hypothesise that switching to a slower growing — but less sensitive — phenotype helps bacteria to develop resistance by providing alternative, faster evolutionary routes to resistance.
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14
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Vo JL, Martínez Ortiz GC, Subedi P, Keerthikumar S, Mathivanan S, Paxman JJ, Heras B. Autotransporter Adhesins in Escherichia coli Pathogenesis. Proteomics 2017; 17. [PMID: 28665015 DOI: 10.1002/pmic.201600431] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2017] [Revised: 06/21/2017] [Indexed: 12/14/2022]
Abstract
Most bacteria produce adhesion molecules to facilitate the interaction with host cells and establish successful infections. An important group of bacterial adhesins belong to the autotransporter (AT) superfamily, the largest group of secreted and outer membrane proteins in Gram-negative bacteria. AT adhesins possess diverse functions that facilitate bacterial colonisation, survival and persistence, and as such are often associated with increased bacterial fitness and pathogenic potential. In this review, we will describe AIDA-I type AT adhesins, which comprise the biggest and most diverse group in the AT family. We will focus on Escherichia coli proteins and define general aspects of their biogenesis, distribution, structural properties and key roles in infection.
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Affiliation(s)
- Julieanne L Vo
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia
| | - Gabriela Constanza Martínez Ortiz
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia
| | - Pramod Subedi
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia
| | - Shivakumar Keerthikumar
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia
| | - Suresh Mathivanan
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia
| | - Jason J Paxman
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia
| | - Begoña Heras
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia
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15
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Bauer M, Graf IR, Ngampruetikorn V, Stephens GJ, Frey E. Exploiting ecology in drug pulse sequences in favour of population reduction. PLoS Comput Biol 2017; 13:e1005747. [PMID: 28957328 DOI: 10.1371/journal.pcbi.1005747] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Revised: 10/16/2017] [Accepted: 08/23/2017] [Indexed: 11/19/2022] Open
Abstract
A deterministic population dynamics model involving birth and death for a two-species system, comprising a wild-type and more resistant species competing via logistic growth, is subjected to two distinct stress environments designed to mimic those that would typically be induced by temporal variation in the concentration of a drug (antibiotic or chemotherapeutic) as it permeates through the population and is progressively degraded. Different treatment regimes, involving single or periodical doses, are evaluated in terms of the minimal population size (a measure of the extinction probability), and the population composition (a measure of the selection pressure for resistance or tolerance during the treatment). We show that there exist timescales over which the low-stress regime is as effective as the high-stress regime, due to the competition between the two species. For multiple periodic treatments, competition can ensure that the minimal population size is attained during the first pulse when the high-stress regime is short, which implies that a single short pulse can be more effective than a more protracted regime. Our results suggest that when the duration of the high-stress environment is restricted, a treatment with one or multiple shorter pulses can produce better outcomes than a single long treatment. If ecological competition is to be exploited for treatments, it is crucial to determine these timescales, and estimate for the minimal population threshold that suffices for extinction. These parameters can be quantified by experiment.
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Jauffred L, Munk Vejborg R, Korolev KS, Brown S, Oddershede LB. Chirality in microbial biofilms is mediated by close interactions between the cell surface and the substratum. ISME J 2017; 11:1688-701. [PMID: 28362723 DOI: 10.1038/ismej.2017.19] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Revised: 12/22/2016] [Accepted: 01/18/2017] [Indexed: 11/29/2022]
Abstract
From microbial biofilms to human migrations, spatial competition is central to the evolutionary history of many species. The boundary between expanding populations is the focal point of competition for space and resources and is of particular interest in ecology. For all Escherichia coli strains studied here, these boundaries move in a counterclockwise direction even when the competing strains have the same fitness. We find that chiral growth of bacterial colonies is strongly suppressed by the expression of extracellular features such as adhesive structures and pili. Experiments with other microbial species show that chiral growth is found in other bacteria and exclude cell wall biosynthesis and anisotropic shape as the primary causes of chirality. Instead, intimate contact with the substratum is necessary for chirality. Our results demonstrate that through a handful of surface molecules cells can fundamentally reorganize their migration patterns, which might affect intra- and interspecific competitions through colony morphology or other mechanisms.
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17
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Sarkar S, Roberts LW, Phan MD, Tan L, Lo AW, Peters KM, Paterson DL, Upton M, Ulett GC, Beatson SA, Totsika M, Schembri MA. Comprehensive analysis of type 1 fimbriae regulation in fimB-null strains from the multidrug resistant Escherichia coli ST131 clone. Mol Microbiol 2016; 101:1069-87. [PMID: 27309594 DOI: 10.1111/mmi.13442] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/13/2016] [Indexed: 12/17/2022]
Abstract
Uropathogenic Escherichia coli (UPEC) of sequence type 131 (ST131) are a pandemic multidrug resistant clone associated with urinary tract and bloodstream infections. Type 1 fimbriae, a major UPEC virulence factor, are essential for ST131 bladder colonization. The globally dominant sub-lineage of ST131 strains, clade C/H30-R, possess an ISEc55 insertion in the fimB gene that controls phase-variable type 1 fimbriae expression via the invertible fimS promoter. We report that inactivation of fimB in these strains causes altered regulation of type 1 fimbriae expression. Using a novel read-mapping approach based on Illumina sequencing, we demonstrate that 'off' to 'on' fimS inversion is reduced in these strains and controlled by recombinases encoded by the fimE and fimX genes. Unlike typical UPEC strains, the nucleoid-associated H-NS protein does not strongly repress fimE transcription in clade C ST131 strains. Using a genetic screen to identify novel regulators of fimE and fimX in the clade C ST131 strain EC958, we defined a new role for the guaB gene in the regulation of type 1 fimbriae and in colonisation of the mouse bladder. Our results provide a comprehensive analysis of type 1 fimbriae regulation in ST131, and highlight important differences in its control compared to non-ST131 UPEC.
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Affiliation(s)
- Sohinee Sarkar
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, 4072, Australia.,Australian Infectious Disease Research Centre, The University of Queensland, Brisbane, Queensland, 4072, Australia.,Institute of Health and Biomedical Innovation, School of Biomedical Sciences, Queensland University of Technology, Brisbane, Queensland, 4059, Australia
| | - Leah W Roberts
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, 4072, Australia.,Australian Infectious Disease Research Centre, The University of Queensland, Brisbane, Queensland, 4072, Australia
| | - Minh-Duy Phan
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, 4072, Australia.,Australian Infectious Disease Research Centre, The University of Queensland, Brisbane, Queensland, 4072, Australia
| | - Lendl Tan
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, 4072, Australia.,Australian Infectious Disease Research Centre, The University of Queensland, Brisbane, Queensland, 4072, Australia
| | - Alvin W Lo
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, 4072, Australia.,Australian Infectious Disease Research Centre, The University of Queensland, Brisbane, Queensland, 4072, Australia
| | - Kate M Peters
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, 4072, Australia.,Australian Infectious Disease Research Centre, The University of Queensland, Brisbane, Queensland, 4072, Australia
| | - David L Paterson
- Australian Infectious Disease Research Centre, The University of Queensland, Brisbane, Queensland, 4072, Australia.,Royal Brisbane and Women's Hospital, University of Queensland Centre for Clinical Research, Brisbane, Queensland, 4029, Australia
| | - Mathew Upton
- Plymouth University Peninsula Schools of Medicine and Dentistry, Plymouth, PL4 8AA, UK
| | - Glen C Ulett
- School of Medical Science, Menzies Health Institute Queensland, Griffith University, Gold Coast, Queensland, 4222, Australia
| | - Scott A Beatson
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, 4072, Australia. .,Australian Infectious Disease Research Centre, The University of Queensland, Brisbane, Queensland, 4072, Australia.
| | - Makrina Totsika
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, 4072, Australia. .,Australian Infectious Disease Research Centre, The University of Queensland, Brisbane, Queensland, 4072, Australia. .,Institute of Health and Biomedical Innovation, School of Biomedical Sciences, Queensland University of Technology, Brisbane, Queensland, 4059, Australia.
| | - Mark A Schembri
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, 4072, Australia. .,Australian Infectious Disease Research Centre, The University of Queensland, Brisbane, Queensland, 4072, Australia.
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18
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Lin WH, Kussell E. Complex Interplay of Physiology and Selection in the Emergence of Antibiotic Resistance. Curr Biol 2016; 26:1486-93. [PMID: 27212408 DOI: 10.1016/j.cub.2016.04.015] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2015] [Revised: 02/10/2016] [Accepted: 04/01/2016] [Indexed: 11/19/2022]
Abstract
Emergence of antibiotic resistance, an evolutionary process of major importance for human health [1], often occurs under changing levels of antibiotics. Selective sweeps, in which resistant cells become dominant in the population, are a critical step in this process [2]. While resistance emergence has been studied in laboratory experiments [3-8], the full progression of selective sweeps under fluctuating stress, from stochastic events in single cells to fixation in populations, has not been characterized. Here, we study fluctuating selection using Escherichia coli populations engineered with a stochastic switch controlling tetracycline resistance. Using microfluidics and live-cell imaging, we treat multiple E. coli populations with the same total amount of tetracycline but administered in different temporal patterns. We find that populations exposed to either short or long antibiotic pulses are likely to develop resistance through selective sweeps, whereas intermediate pulses allow higher growth rates but suppress selective sweeps. On the basis of single-cell measurements and a dynamic growth model, we identify the major determinants of population growth and show that both physiological memory and environmental durations can strongly modulate the emergence of resistance. Our detailed quantification in a model synthetic system provides key lessons on the interaction between single-cell physiology and selection that should inform the design of treatment regimens [9-12] and the analysis of phenotypically diverse populations adapting under fluctuating selection [13-17].
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Affiliation(s)
- Wei-Hsiang Lin
- Center for Genomics and Systems Biology, Department of Biology, New York University, 12 Waverly Place, New York, NY 10003, USA
| | - Edo Kussell
- Center for Genomics and Systems Biology, Department of Biology, New York University, 12 Waverly Place, New York, NY 10003, USA; Department of Physics, New York University, 4 Washington Place, New York, NY 10003, USA.
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19
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Shin JE, Lin C, Lim HN. Horizontal transfer of DNA methylation patterns into bacterial chromosomes. Nucleic Acids Res 2016; 44:4460-71. [PMID: 27084942 PMCID: PMC4872104 DOI: 10.1093/nar/gkw230] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2016] [Accepted: 03/29/2016] [Indexed: 12/21/2022] Open
Abstract
Horizontal gene transfer (HGT) is the non-inherited acquisition of novel DNA sequences. HGT is common and important in bacteria because it enables the rapid generation of new phenotypes such as antibiotic resistance. Here we show that in vivo and in vitro DNA methylation patterns can be horizontally transferred into bacterial chromosomes to program cell phenotypes. The experiments were performed using a synthetic system in Escherichia coli where different DNA methylation patterns within the cis-regulatory sequence of the agn43 gene turn on or off a fluorescent reporter (CFP). With this system we demonstrated that DNA methylation patterns not only accompany the horizontal transfer of genes into the bacterial cytoplasm but can be transferred into chromosomes by: (i) bacteriophage P1 transduction; and (ii) transformation of extracellular synthetic DNA. We also modified the experimental system by replacing CFP with the SgrS small RNA, which regulates glucose and methyl α-D-glucoside uptake, and showed that horizontally acquired DNA methylation patterns can increase or decrease cell fitness. That is, horizontally acquired DNA methylation patterns can result in the selection for and against cells that have HGT. Findings from these proof-of-concept experiments have applications in synthetic biology and potentially broad implications for bacterial adaptation and evolution.
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Affiliation(s)
- Jung-Eun Shin
- Department of Integrative Biology, University of California Berkeley, CA 94720-3140, USA
| | - Chris Lin
- Department of Integrative Biology, University of California Berkeley, CA 94720-3140, USA
| | - Han N Lim
- Department of Integrative Biology, University of California Berkeley, CA 94720-3140, USA
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20
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Bak G, Lee J, Suk S, Kim D, Young Lee J, Kim KS, Choi BS, Lee Y. Identification of novel sRNAs involved in biofilm formation, motility, and fimbriae formation in Escherichia coli. Sci Rep 2015; 5:15287. [PMID: 26469694 DOI: 10.1038/srep15287] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2015] [Accepted: 09/22/2015] [Indexed: 01/08/2023] Open
Abstract
Bacterial small RNAs (sRNAs) are known regulators in many physiological processes. In Escherichia coli, a large number of sRNAs have been predicted, among which only about a hundred are experimentally validated. Despite considerable research, the majority of their functions remain uncovered. Therefore, collective analysis of the roles of sRNAs in specific cellular processes may provide an effective approach to identify their functions. Here, we constructed a collection of plasmids overexpressing 99 individual sRNAs, and analyzed their effects on biofilm formation and related phenotypes. Thirty-three sRNAs significantly affecting these cellular processes were identified. No consistent correlations were observed, except that all five sRNAs suppressing type I fimbriae inhibited biofilm formation. Interestingly, IS118, yet to be characterized, suppressed all the processes. Our data not only reveal potentially critical functions of individual sRNAs in biofilm formation and other phenotypes but also highlight the unexpected complexity of sRNA-mediated metabolic pathways leading to these processes.
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21
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Shippy DC, Fadl AA. RNA modification enzymes encoded by the gid operon: Implications in biology and virulence of bacteria. Microb Pathog 2015; 89:100-7. [PMID: 26427881 DOI: 10.1016/j.micpath.2015.09.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 09/23/2015] [Indexed: 01/10/2023]
Abstract
Ribonucleic acid (RNA) molecules consist of numerous chemically modified nucleosides that are highly conserved in eukarya, archeae, and bacteria, while others are unique to each domain of life. In bacteria, hundreds of RNA modification enzymes have been identified and implicated in biological pathways associated with many cell processes. The glucose-inhibited division (gid) operon encodes genes for two RNA modification enzymes named GidA and GidB. Studies have shown GidA is essential for the proper biosynthesis of 5-methylaminomethyl-2-thiouridine (mnm(5)s(2)U) of bacterial transfer RNA (tRNA) with GidB responsible for the methylation of the 16S ribosomal RNA (rRNA). Furthermore, deletion of gidA and gidB has shown to alter numerous bacterial properties like virulence, stress response, morphology, growth, antibiotic susceptibility, and others. In this review, we discuss the present knowledge of the RNA modification enzymes GidA and GidB, and their potential role in the biology and virulence of bacteria.
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Affiliation(s)
- Daniel C Shippy
- Department of Animal Sciences, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Amin A Fadl
- Department of Animal Sciences, University of Wisconsin-Madison, Madison, WI 53706, USA.
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22
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Van Tassell ML, Price NP, Miller MJ. Glycan-specific whole cell affinity chromatography: A versatile microbial adhesion platform. MethodsX 2014; 1:244-50. [PMID: 26150959 PMCID: PMC4473024 DOI: 10.1016/j.mex.2014.10.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2014] [Accepted: 10/20/2014] [Indexed: 11/18/2022] Open
Abstract
We have sought a universal platform for elucidating and exploiting specificity of glycan-mediated adhesion by potentially uncharacterized microorganisms. Several techniques exist to explore microbial interactions with carbohydrate structures. Many are unsuitable for investigating specific mechanisms or uncharacterized organisms, requiring pure cultures, labeling techniques, expensive equipment, or other limitations such as questionable stability, stereospecificity, or scalability. We have adapted an affinity chromatography resin as a model to overcome these drawbacks, among others. It readily allows for the quantification, selection, and manipulation of target organisms based on interactions with glycan ligands. To maximize its utility as a selective screening method, we have constructed the tool such that it:Promotes whole-cell interactions using viable, unaltered cells. Provides robust spatial interactions with target glycans, presented with controlled stereo-specificity, for high affinity/avidity interactions that reflect a complex in vivo matrix. Has the ability to utilize any reducing glycan, is quick, efficient, safe, and affordable to construct, and is scalable and reusable for multiple applications.
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Affiliation(s)
- Maxwell L. Van Tassell
- Department of Food Science and Human Nutrition, University of Illinois, Urbana, IL 61801, USA
| | - Neil P.J. Price
- National Center for Agricultural Utilization Research, Agricultural Research Service, U.S. Department of Agriculture, Peoria, IL 61604, USA
| | - Michael J. Miller
- Department of Food Science and Human Nutrition, University of Illinois, Urbana, IL 61801, USA
- Corresponding author at: 439 Bevier Hall, 905 S. Goodwin Avenue, Urbana, IL 61801, USA. Tel.: +1 217 244 1973; fax: +1 217 265 0925.
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23
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Tang Y, Kim H, Singh AK, Aroonnual A, Bae E, Rajwa B, Fratamico PM, Bhunia AK. Light scattering sensor for direct identification of colonies of Escherichia coli serogroups O26, O45, O103, O111, O121, O145 and O157. PLoS One 2014; 9:e105272. [PMID: 25136836 PMCID: PMC4138183 DOI: 10.1371/journal.pone.0105272] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2014] [Accepted: 07/18/2014] [Indexed: 12/16/2022] Open
Abstract
Background Shiga-toxin producing Escherichia coli (STEC) have emerged as important foodborne pathogens, among which seven serogroups (O26, O45, O103, O111, O121, O145, O157) are most frequently implicated in human infection. The aim was to determine if a light scattering sensor can be used to rapidly identify the colonies of STEC serogroups on selective agar plates. Methodology/Principal Findings Initially, a total of 37 STEC strains representing seven serovars were grown on four different selective agar media, including sorbitol MacConkey (SMAC), Rainbow Agar O157, BBL CHROMagarO157, and R&F E. coli O157:H7, as well as nonselective Brain Heart Infusion agar. The colonies were scanned by an automated light scattering sensor, known as BARDOT (BActerial Rapid Detection using Optical scattering Technology), to acquire scatter patterns of STEC serogroups, and the scatter patterns were analyzed using an image classifier. Among all of the selective media tested, both SMAC and Rainbow provided the best differentiation results allowing multi-class classification of all serovars with an average accuracy of more than 90% after 10–12 h of growth, even though the colony appearance was indistinguishable at that early stage of growth. SMAC was chosen for exhaustive scatter image library development, and 36 additional strains of O157:H7 and 11 non-O157 serovars were examined, with each serogroup producing unique differential scatter patterns. Colony scatter images were also tested with samples derived from pure and mixed cultures, as well as experimentally inoculated food samples. BARDOT accurately detected O157 and O26 serovars from a mixed culture and also from inoculated lettuce and ground beef (10-h broth enrichment +12-h on-plate incubation) in the presence of natural background microbiota in less than 24 h. Conclusions BARDOT could potentially be used as a screening tool during isolation of the most important STEC serovars on selective agar plates from food samples in less than 24 h.
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Affiliation(s)
- Yanjie Tang
- Molecular Food Microbiology Laboratory, Department of Food Science, Purdue University, West Lafayette, Indiana, United States of America
| | - Huisung Kim
- School of Mechanical Engineering, Purdue University, West Lafayette, Indiana, United States of America
| | - Atul K. Singh
- Molecular Food Microbiology Laboratory, Department of Food Science, Purdue University, West Lafayette, Indiana, United States of America
| | - Amornrat Aroonnual
- Molecular Food Microbiology Laboratory, Department of Food Science, Purdue University, West Lafayette, Indiana, United States of America
| | - Euiwon Bae
- School of Mechanical Engineering, Purdue University, West Lafayette, Indiana, United States of America
| | - Bartek Rajwa
- Bindley Bioscience Center, Purdue University, West Lafayette, Indiana, United States of America
| | - Pina M. Fratamico
- USDA-ARS, Eastern Regional Research Center, Wyndmoor, Pennsylvania, United States of America
| | - Arun K. Bhunia
- Molecular Food Microbiology Laboratory, Department of Food Science, Purdue University, West Lafayette, Indiana, United States of America
- Department of Comparative Pathobiology, Purdue University, West Lafayette, Indiana, United States of America
- * E-mail:
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24
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Hung M, Chang E, Hussein R, Frazier K, Shin JE, Sagawa S, Lim HN. Modulating the frequency and bias of stochastic switching to control phenotypic variation. Nat Commun 2014; 5:4574. [PMID: 25087841 DOI: 10.1038/ncomms5574] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Accepted: 07/02/2014] [Indexed: 12/29/2022] Open
Abstract
Mechanisms that control cell-to-cell variation in gene expression ('phenotypic variation') can determine a population's growth rate, robustness, adaptability and capacity for complex behaviours. Here we describe a general strategy (termed FABMOS) for tuning the phenotypic variation and mean expression of cell populations by modulating the frequency and bias of stochastic transitions between 'OFF' and 'ON' expression states of a genetic switch. We validated the strategy experimentally using a synthetic fim switch in Escherichia coli. Modulating the frequency of switching can generate a bimodal (low frequency) or a unimodal (high frequency) population distribution with the same mean expression. Modulating the bias as well as the frequency of switching can generate a spectrum of bimodal and unimodal distributions with the same mean expression. This remarkable control over phenotypic variation, which cannot be easily achieved with standard gene regulatory mechanisms, has many potential applications for synthetic biology, engineered microbial ecosystems and experimental evolution.
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25
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Gómez-Gómez JM, Amils R. Crowning: a novel Escherichia coli colonizing behaviour generating a self-organized corona. BMC Res Notes 2014; 7:108. [PMID: 24568619 DOI: 10.1186/1756-0500-7-108] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2013] [Accepted: 02/17/2014] [Indexed: 12/03/2022] Open
Abstract
Background Encased in a matrix of extracellular polymeric substances (EPS) composed of flagella, adhesins, amyloid fibers (curli), and exopolysaccharides (cellulose, β-1,6-N-acetyl-D-glucosamine polymer-PGA-, colanic acid), the bacteria Escherichia coli is able to attach to and colonize different types of biotic and abiotic surfaces forming biofilms and colonies of intricate morphological architectures. Many of the biological aspects that underlie the generation and development of these E. coli’s formations are largely poorly understood. Results Here, we report the characterization of a novel E. coli sessile behaviour termed "crowning" due to the bacterial generation of a new 3-D architectural pattern: a corona. This bacterial pattern is formed by joining bush-like multilayered "coronal flares or spikes" arranged in a ring, which self-organize through the growth, self-clumping and massive self-aggregation of cells tightly interacting inside semisolid agar on plastic surfaces. Remarkably, the corona’s formation is developed independently of the adhesiveness of the major components of E. coli’s EPS matrix, the function of chemotaxis sensory system, type 1 pili and the biofilm master regulator CsgD, but its formation is suppressed by flagella-driven motility and glucose. Intriguingly, this glucose effect on the corona development is not mediated by the classical catabolic repression system, the cyclic AMP (cAMP)-cAMP receptor protein (CRP) complex. Thus, corona formation departs from the canonical regulatory transcriptional core that controls biofilm formation in E. coli. Conclusions With this novel "crowning" activity, E. coli expands its repertoire of colonizing collective behaviours to explore, invade and exploit environments whose critical viscosities impede flagella driven-motility.
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26
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Chauhan A, Sakamoto C, Ghigo JM, Beloin C. Did I pick the right colony? Pitfalls in the study of regulation of the phase variable antigen 43 adhesin. PLoS One 2013; 8:e73568. [PMID: 24039985 PMCID: PMC3764049 DOI: 10.1371/journal.pone.0073568] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Accepted: 07/21/2013] [Indexed: 11/27/2022] Open
Abstract
Ag43 is an abundant outer membrane autotransporter adhesin present in most commensal and pathogenic Escherichia coli. Expression of the agn43 gene is characterized by a regulated reversible switch or phase variation between the agn43 ON and agn43 OFF states. Although the agn43 regulatory switch leads to a heterogeneous population of ON and OFF bacteria, studies of Ag43 seldom consider potential biases associated with phase variation. We monitored agn43 ON/OFF phase-variation status genetically and phenotypically and we show that the use of populations with random agn43 ON or OFF status could result in misleading conclusions about Ag43 function or regulation. In particular, we demonstrate that Lrp and MqsR, previously identified as agn43 regulators, do not regulate agn43 expression or ON/OFF switch frequency. We also show that biofilm formation in dynamic flow conditions does not influence agn43 ON/OFF switching but physically selects aggregating agn43 ON cells. This indicates that misinterpretation is possible when studying gene expression within biofilms. Finally, we provide evidence that ignoring the initial agn43 ON/OFF status of the E. coli populations studied is likely to bias analyses of phenotypes associated with other E. coli adhesins. This study therefore emphasizes the importance of monitoring Ag43 phase variation and indicates that caution is required when interpreting experiments using strains that are neither deleted for agn43 nor carefully assessed for agn43 ON/OFF status.
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Affiliation(s)
- Ashwini Chauhan
- Institut Pasteur, Unité de Génétique des Biofilms, Département de Microbiologie, Paris, France
| | - Chizuko Sakamoto
- Institut Pasteur, Unité de Génétique des Biofilms, Département de Microbiologie, Paris, France
- Université Paris Diderot, Sorbonne Paris Cité, cellule Pasteur, Paris, France
| | - Jean-Marc Ghigo
- Institut Pasteur, Unité de Génétique des Biofilms, Département de Microbiologie, Paris, France
| | - Christophe Beloin
- Institut Pasteur, Unité de Génétique des Biofilms, Département de Microbiologie, Paris, France
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27
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Puentes-Téllez PE, Kovács ÁT, Kuipers OP, van Elsas JD. Comparative genomics and transcriptomics analysis of experimentally evolved Escherichia coli MC1000 in complex environments. Environ Microbiol 2013; 16:856-70. [PMID: 24033913 DOI: 10.1111/1462-2920.12239] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2013] [Accepted: 07/30/2013] [Indexed: 11/30/2022]
Abstract
It has recently become feasible to study the basis and nature of evolutionary changes in bacteria in an experimental setting using defined media. However, assessment of adaptive changes in complex environments has been scarce. In an effort to describe the responses in such environments, we unravel, in a comparative approach, the transcriptional and genetic profiles of 19 Escherichia coli strains that evolved in Luria Bertani medium under three different oxygen regimes over 1000 generations. A positive relationship between upregulation of gene expression and the number of mutations was observed, suggesting that a number of metabolic pathways were activated. Phenotypic polymorphisms were observed in parallel cultures, of which some were related with mutations at the regulatory level. Non-parallel responses were observed at the intrapopulational level, which is indicative of diversifying selection. Parallel responses encompassed transcriptome diversity, and their effects were directly affected by differing genomic backgrounds. A fluctuating selective force produced higher phenotypic diversity compared with constant forces. This study demonstrates how phenotypic innovations may depend on the relationship between genomic changes and local ecological conditions. Using both comparative genomics and transcriptomics approaches, the results help elucidating various adaptive responses in cultures in unexplored complex environments.
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28
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Mela F, Fritsche K, de Boer W, van den Berg M, van Veen JA, Maharaj NN, Leveau JHJ. Comparative genomics of bacteria from the genus Collimonas: linking (dis)similarities in gene content to phenotypic variation and conservation. Environ Microbiol Rep 2012; 4:424-432. [PMID: 23760828 DOI: 10.1111/j.1758-2229.2012.00336.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Collimonas is a genus of soil bacteria comprising three recognized species: C. fungivorans, C. pratensis and C. arenae. Collimonads share the ability to degrade chitin (chitinolysis), feed on living fungal hyphae (mycophagy), and dissolve minerals (weathering), but vary in their inhibition of fungi (fungistasis). To better understand this phenotypic variability, we analysed the genomic content of four strains representing three Collimonas species (Ter14, Ter6, Ter91 and Ter10) by hybridization to a microarray based on reference strain C. fungivorans Ter331. The analysis revealed genes unique to strain Ter331 (e.g. those on the extrachromosomal element pTer331) and genes present in some but not all of the tested strains. Among the latter were several candidates that may contribute to fungistasis, including genes for the production and secretion of antifungals. We hypothesize that differential possession of these genes underlies the specialization of Collimonas strains towards different fungal hosts. We identified a set of 136 genes that were common in all tested Collimonas strains, but absent from the genomes of three other members of the family Oxalobacteraceae. Predicted products of these 'Collimonas core' genes include lytic, secreted enzymes such as chitinases, peptidases, nucleases and phosphatases with a putative role in mycophagy and weathering.
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Affiliation(s)
- F Mela
- Department of Microbial Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, the Netherlands Institute of Biology, Leiden University, Leiden, the Netherlands Department of Plant Pathology, University of California, Davis, CA 95616, USA
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29
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Hekstra DR, Leibler S. Contingency and statistical laws in replicate microbial closed ecosystems. Cell 2012; 149:1164-73. [PMID: 22632978 DOI: 10.1016/j.cell.2012.03.040] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2011] [Revised: 02/10/2012] [Accepted: 03/09/2012] [Indexed: 11/23/2022]
Abstract
Contingency, the persistent influence of past random events, pervades biology. To what extent, then, is each course of ecological or evolutionary dynamics unique, and to what extent are these dynamics subject to a common statistical structure? Addressing this question requires replicate measurements to search for emergent statistical laws. We establish a readily replicated microbial closed ecosystem (CES), sustaining its three species for years. We precisely measure the local population density of each species in many CES replicates, started from the same initial conditions and kept under constant light and temperature. The covariation among replicates of the three species densities acquires a stable structure, which could be decomposed into discrete eigenvectors, or "ecomodes." The largest ecomode dominates population density fluctuations around the replicate-average dynamics. These fluctuations follow simple power laws consistent with a geometric random walk. Thus, variability in ecological dynamics can be studied with CES replicates and described by simple statistical laws.
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Mikheil DM, Shippy DC, Eakley NM, Okwumabua OE, Fadl AA. Deletion of gene encoding methyltransferase (gidB) confers high-level antimicrobial resistance in Salmonella. J Antibiot (Tokyo) 2012; 65:185-92. [DOI: 10.1038/ja.2012.5] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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de Pace F, Nakazato G, Pacheco A, de Paiva JB, Sperandio V, da Silveira WD. The type VI secretion system plays a role in type 1 fimbria expression and pathogenesis of an avian pathogenic Escherichia coli strain. Infect Immun 2010; 78:4990-8. [PMID: 20855516 DOI: 10.1128/IAI.00531-10] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Avian pathogenic Escherichia coli (APEC) strains frequently cause extraintestinal infections and are responsible for significant economic losses in the poultry industry worldwide. APEC isolates are closely related to human extraintestinal pathogenic E. coli (ExPEC) strains and may also act as pathogens for humans. Known APEC virulence factors include adhesins such as type 1 fimbriae and curli, iron acquisition systems, and cytotoxins. Here we show that APEC strain SEPT362, isolated from a septicemic hen, expresses a type VI secretion system (T6SS); causes cytoskeleton rearrangements; and invades epithelial cells, replicates within macrophages, and causes lethal disease in chicks. To assess the contribution of the T6SS to SEPT362 pathogenesis, we generated two mutants, hcp (which encodes a protein suggested to be both secreted and a structural component of the T6SS) and clpV (encoding the T6SS ATPase). Both mutants showed decreased adherence and actin rearrangement on epithelial cells. However, only the hcp mutant presented a mild decrease in its ability to invade epithelial cells, and none of these mutants were defective for intramacrophage replication. Transcriptome studies showed that the level of expression of type 1 fimbriae was decreased in these mutants, which may account for the diminished adhesion and invasion of epithelial cells. The T6SS seems to be important for the disease process, given that both mutants were attenuated for infection in chicks. These results suggest that the T6SS influences the expression of type 1 fimbriae and contributes to APEC pathogenesis.
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Korea CG, Badouraly R, Prevost MC, Ghigo JM, Beloin C. Escherichia coli K-12 possesses multiple cryptic but functional chaperone-usher fimbriae with distinct surface specificities. Environ Microbiol 2010; 12:1957-77. [PMID: 20345943 DOI: 10.1111/j.1462-2920.2010.02202.x] [Citation(s) in RCA: 127] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Commensal and pathogenic Escherichia coli adherence to host and environmental surfaces is mediated by a variety of adhesins. Although extensively studied as a model bacterium, 34% of the genes in the E. coli K-12 genome have no known function. We hypothesized that some of them may correspond to functional adhesins. We characterized E. coli K-12 ycb, ybg, yfc, yad, yra, sfm and yeh operons, which display sequence and organizational homologies to type 1 fimbriae exported by the chaperone/usher pathway. We showed that, although these operons are poorly expressed under laboratory conditions, six of them are nevertheless functional when expressed, and promote adhesion to abiotic and/or epithelial cell surfaces. While the studied fimbriae display different binding specificities, we obtained evidence of synergy/interference with other adhesins such as Ag43 or type 1 fimbriae. We showed that their expression is under the negative control of H-NS and, except for yad, subjected to cAMP receptor protein-mediated activation and carbon catabolite repression. These results therefore demonstrate that ycb, yfc, yad, yra, sfm and yeh operons encode cryptic but functional fimbriae adhesins whose expression following environmental modifications could contribute to E. coli's ability to adhere to and colonize a wide diversity of surfaces in its various ecological niches.
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Affiliation(s)
- Charalampia-Georgia Korea
- Institut Pasteur, Unité de Génétique des Biofilms, CNRS URA 2172, 25-28 rue du Dr Roux, 750724 Paris Cedex 15, France
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Studier FW, Daegelen P, Lenski RE, Maslov S, Kim JF. Understanding the differences between genome sequences of Escherichia coli B strains REL606 and BL21(DE3) and comparison of the E. coli B and K-12 genomes. J Mol Biol 2009; 394:653-80. [PMID: 19765592 DOI: 10.1016/j.jmb.2009.09.021] [Citation(s) in RCA: 147] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2009] [Revised: 09/09/2009] [Accepted: 09/10/2009] [Indexed: 11/20/2022]
Abstract
Each difference between the genome sequences of Escherichia coli B strains REL606 and BL21(DE3) can be interpreted in light of known laboratory manipulations plus a gene conversion between ribosomal RNA operons. Two treatments with 1-methyl-3-nitro-1-nitrosoguanidine in the REL606 lineage produced at least 93 single-base-pair mutations ( approximately 90% GC-to-AT transitions) and 3 single-base-pair GC deletions. Two UV treatments in the BL21(DE3) lineage produced only 4 single-base-pair mutations but 16 large deletions. P1 transductions from K-12 into the two B lineages produced 317 single-base-pair differences and 9 insertions or deletions, reflecting differences between B DNA in BL21(DE3) and integrated restriction fragments of K-12 DNA inherited by REL606. Two sites showed selective enrichment of spontaneous mutations. No unselected spontaneous single-base-pair mutations were evident. The genome sequences revealed that a progenitor of REL606 had been misidentified, explaining initially perplexing differences. Limited sequencing of other B strains defined characteristic properties of B and allowed assembly of the inferred genome of the ancestral B of Delbrück and Luria. Comparison of the B and K-12 genomes shows that more than half of the 3793 proteins of their basic genomes are predicted to be identical, although approximately 310 appear to be functional in either B or K-12 but not in both. The ancestral basic genome appears to have had approximately 4039 coding sequences occupying approximately 4.0 Mbp. Repeated horizontal transfer from diverged Escherichia coli genomes and homologous recombination may explain the observed variable distribution of single-base-pair differences. Fifteen sites are occupied by phage-related elements, but only six by comparable elements at the same site. More than 50 sites are occupied by IS elements in both B and K, 16 in common, and likely founding IS elements are identified. A signature of widespread cryptic phage P4-type mobile elements was identified. Complex deletions (dense clusters of small deletions and substitutions) apparently removed nonessential genes from approximately 30 sites in the basic genomes.
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Affiliation(s)
- F William Studier
- Biology Department, Brookhaven National Laboratory, PO Box 5000, Upton, NY 11973-5000, USA.
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Abstract
In this study we report on a novel structural phenotype in Escherichia coli biofilms: cellular chain formation. Biofilm chaining in E. coli K-12 was found to occur primarily by clonal expansion, but was not due to filamentous growth. Rather, chain formation was the result of intercellular interactions facilitated by antigen 43 (Ag43), a self-associating autotransporter (SAAT) protein, which has previously been implicated in auto-aggregation and biofilm formation. Immunofluorescence microscopy suggested that Ag43 was concentrated at or near the cell poles, although when the antigen was highly overexpressed, a much more uniform distribution was seen. Immunofluorescence microscopy also indicated that other parameters, including dimensional constraints (flow, growth alongside a surface), may also affect the final biofilm architecture. Moreover, chain formation was affected by other surface structures; type I fimbriae expression significantly reduced cellular chain formation, presumably by steric hindrance. Cellular chain formation did not appear to be specific to E. coli K-12. Although many urinary tract infection (UTI) isolates were found to form rather homogeneous, flat biofilms, three isolates, including the prototypic asymptomatic bacteriuria strain, 83972, formed highly elaborate cellular chains during biofilm growth in human urine. Combined, these results illustrate the diversity of biofilm architectures that can be observed even within a single microbial species.
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Affiliation(s)
- Rebecca Munk Vejborg
- Microbial Genomics Group, Centre for Biological Sequence Analysis, Department of Systems Biology, Technical University of Denmark, Building 301, DK-2800 Kgs. Lyngby, Denmark
| | - Per Klemm
- Microbial Genomics Group, Centre for Biological Sequence Analysis, Department of Systems Biology, Technical University of Denmark, Building 301, DK-2800 Kgs. Lyngby, Denmark
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Lutterodt G, Basnet M, Foppen JWA, Uhlenbrook S. The effect of surface characteristics on the transport of multiple Escherichia coli isolates in large scale columns of quartz sand. Water Res 2009; 43:595-604. [PMID: 19042002 DOI: 10.1016/j.watres.2008.11.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2008] [Revised: 09/30/2008] [Accepted: 11/07/2008] [Indexed: 05/27/2023]
Abstract
Bacteria properties play an important role in the transport of bacteria in groundwater, but their role, especially for longer transport distances (>0.5 m) has not been studied. Thereto, we studied the effects of cell surface hydrophobicity, outer surface potential (OSP), cell sphericity, motility, and Ag43 protein expression on the outer cell surface for a number of E. coli strains, obtained from the environment on their transport behavior in columns of saturated quartz sand of 5 m height in two solutions: demineralized (DI) water and artificial groundwater (AGW). In DI water, sticking efficiencies ranged between 0.1 and 0.4 at the column inlet, and then decreased with transport distance to 0.02-0.2. In AGW, sticking efficiencies were on average 1log-unit higher than those in DI (water). Bacteria motility and Ag43 expression affected attachment with a (high) statistical significance. In contrast, hydrophobicity, OSP and cell sphericity did not significantly correlate with sticking efficiency. However, for transport distances more than 0.33 m, the correlation between sticking efficiency, Ag43 expression, and motility became insignificant. We concluded that Ag43 and motility played an important role in E. coli attachment to quartz grain surfaces, and that the transport distance dependent sticking efficiency reductions were caused by motility and Ag43 expression variations within a population. The implication of our findings is that less motile bacteria with little or no Ag43 expression may travel longer distances once they enter groundwater environments. In future studies, the possible effect of bacteria surface structures, like fimbriae, pili and surface proteins on bacteria attachment need to be considered more systematically in order to arrive at more meaningful inter-population comparisons of the transport behavior of E. coli strains in aquifers.
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Affiliation(s)
- G Lutterodt
- UNESCO-IHE Institute for Water Education, P.O. Box 3015, 2601 DA, Delft, The Netherlands.
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De La Fuente L, Burr TJ, Hoch HC. Autoaggregation of Xylella fastidiosa cells is influenced by type I and type IV pili. Appl Environ Microbiol 2008; 74:5579-82. [PMID: 18641157 PMCID: PMC2546647 DOI: 10.1128/aem.00995-08] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2008] [Accepted: 07/02/2008] [Indexed: 11/20/2022] Open
Abstract
Autoaggregation of widely dispersed Xylella fastidiosa cells into compact cell masses occurred over a period of hours following 7 to 11 days of growth in microfluidic chambers. Studies involving the use of mutants defective in polarly positioned type I (fimA-negative), type IV (pilB-negative), or both type I and IV (fimA- and pilO-negative) pili revealed the importance and role of pili in the autoaggregation process.
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Affiliation(s)
- Leonardo De La Fuente
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University-New York State Agricultural Experiment Station, Geneva, NY 14456, USA
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37
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de Luna MDG, Scott-Tucker A, Desvaux M, Ferguson P, Morin NP, Dudley EG, Turner S, Nataro JP, Owen P, Henderson IR. The Escherichia coli biofilm-promoting protein Antigen 43 does not contribute to intestinal colonization. FEMS Microbiol Lett 2008; 284:237-46. [PMID: 18507683 DOI: 10.1111/j.1574-6968.2008.01207.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Abstract Escherichia coli is a versatile organism capable of causing a variety of intestinal and extraintestinal diseases, as well as existing as part of the commensal flora. A variety of factors permit specific attachment to host receptors including fimbrial adhesins and outer membrane proteins such as autotransporters. One of the better characterized autotransporters is Antigen 43 (Ag43), the major phase-variable surface protein of E. coli. Ag43 is associated with bacterial cell-cell aggregation and biofilm formation. Nevertheless, the precise biological significance and contribution to intestinal colonization remain to be elucidated. Here we investigated the contribution of Ag43 to E. coli adherence to intestinal epithelial cells and colonization of the mouse intestine. These investigations revealed that Ag43 increased in vitro adherence of E. coli to epithelial cells by promoting bacterial cell-cell aggregation but that Ag43 did not promote specific interactions with the mammalian cells. Furthermore, Ag43 did not contribute significantly to colonization of the mouse intestine and expression of Ag43 was lost a few days after colonization of the mouse was established. Unexpectedly, considering its similarity to other adhesins, our findings suggest that Ag43 does not act as a direct colonization factor by binding to mammalian cells.
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Affiliation(s)
- Maria das Graças de Luna
- Division of Immunity and Infection, The Medical School, University of Birmingham, Birmingham, UK
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Abstract
Biofilm forming cells are distinctive from the well-investigated planktonic cells and exhibit a different type of gene expression. Several new Escherichia coli genes related to biofilm formation have recently been identified through genomic approaches such as DNA microarray analysis. However, many others involved in this process might have escaped detection due to poor expression, regulatory mechanism, or genetic backgrounds. Here, we screened a collection of single-gene deletion mutants of E. coli named ‘Keio collection’ to identify genes required for biofilm formation. Of the 3985 mutants of non-essential genes in the collection thus examined, 110 showed a reduction in biofilm formation nine of which have not been well characterized yet. Systematic and quantitative analysis revealed the involvement of genes of various functions and reinforced the importance in biofilm formation of the genes for cell surface structures and cell membrane. Characterization of the nine mutants of function-unknown genes indicated that some of them, such as yfgA that genetically interacts with a periplasmic chaperone gene surA together with yciB and yciM, might be required for the integrity of outer membrane.
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Affiliation(s)
- Emma Tabe Eko Niba
- Graduate School of Science and Technology, Kobe University, Kobe, Hyogo 657-8501, Japan
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39
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Ferrières L, Aslam SN, Cooper RM, Clarke DJ. The yjbEFGH locus in Escherichia coli K-12 is an operon encoding proteins involved in exopolysaccharide production. Microbiology (Reading) 2007; 153:1070-1080. [PMID: 17379715 DOI: 10.1099/mic.0.2006/002907-0] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The RcsCDB phosphorelay was originally identified as the main regulator of colanic acid biosynthesis in Escherichia coli K-12. However, recent transcriptomic analyses have identified more than 150 genes belonging to the Rcs regulon, including yjbE, yjbF, yjbG and yjbH. These genes are clustered on the genome and oriented in the same direction but their function remains unknown. In this work it is shown that yjbE, yjbF, yjbG and yjbH are transcribed as a single operon and it is confirmed that the expression of this operon is controlled by the Rcs phosphorelay, in a manner that is dependent on the auxiliary regulatory protein RcsA. Interestingly, Northern blot analysis revealed that the amount of yjbE transcripts in the cell is higher than the amount of yjbEFGH transcripts and it is proposed that this differential expression is mediated by the presence of a strong stem-loop structure in the yjbE-yjbF intergenic region. Finally, evidence is provided that the overexpression of yjbEFGH affects colony morphology and leads to the production of an extracellular polysaccharide that binds Congo red and toluidine blue-O.
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Affiliation(s)
- Lionel Ferrières
- Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, UK
| | - Shazia N Aslam
- Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, UK
| | - Richard M Cooper
- Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, UK
| | - David J Clarke
- Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, UK
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40
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Abstract
Autotransporter proteins constitute a family of outer membrane/secreted proteins that possess unique structural properties that facilitate their independent transport across the bacterial membrane system and final routing to the cell surface. Autotransporter proteins have been identified in a wide range of Gram-negative bacteria and are often associated with virulence functions such as adhesion, aggregation, invasion, biofilm formation and toxicity. The importance of autotransporter proteins is exemplified by the fact that they constitute an essential component of some human vaccines. Autotransporter proteins contain three structural motifs: a signal sequence, a passenger domain and a translocator domain. Here, the structural properties of the passenger and translocator domains of three type Va autotransporter proteins are compared and contrasted, namely pertactin from Bordetella pertussis, the adhesion and penetration protein (Hap) from Haemophilus influenzae and Antigen 43 (Ag43) from Escherichia coli. The Ag43 protein is described in detail to examine how its structure relates to functional properties such as cell adhesion, aggregation and biofilm formation. The widespread occurrence of autotransporter-encoding genes, their apparent uniform role in virulence and their ability to interact with host cells suggest that they may represent rational targets for the design of novel vaccines directed against Gram-negative pathogens.
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Affiliation(s)
- Timothy J Wells
- School of Molecular and Microbial Sciences, University of Queensland, Brisbane, Queensland, Australia
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Abstract
Many studies involving interacting microorganisms would benefit from simple devices able to deposit cells in precisely defined patterns. We describe an inexpensive bacterial piezoelectric inkjet printer (adapted from the design of the POSaM oligonucleotide microarrayer) that can be used to “print out” different strains of bacteria or chemicals in small droplets onto a flat surface at high resolution. The capabilities of this device are demonstrated by printing ordered arrays comprising two bacterial strains labeled with different fluorescent proteins. We also characterized several properties of this piezoelectric printer, such as the droplet volume (of the order of tens of pl), the distribution of number of cells in each droplet, and the dependence of droplet volume on printing frequency. We established the limits of the printing resolution, and determined that the printed viability of Escherichia coli exceeded 98.5%.
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Affiliation(s)
- Jack Merrin
- Laboratory of Living Matter and Center for Physics and Biology, The Rockefeller University, New York, New York, United States of America
| | - Stanislas Leibler
- Laboratory of Living Matter and Center for Physics and Biology, The Rockefeller University, New York, New York, United States of America
| | - John S. Chuang
- Laboratory of Living Matter and Center for Physics and Biology, The Rockefeller University, New York, New York, United States of America
- * To whom correspondence should be addressed. E-mail:
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Ulett GC, Valle J, Beloin C, Sherlock O, Ghigo JM, Schembri MA. Functional analysis of antigen 43 in uropathogenic Escherichia coli reveals a role in long-term persistence in the urinary tract. Infect Immun 2007; 75:3233-44. [PMID: 17420234 PMCID: PMC1932929 DOI: 10.1128/iai.01952-06] [Citation(s) in RCA: 135] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2006] [Revised: 01/28/2007] [Accepted: 04/01/2007] [Indexed: 11/20/2022] Open
Abstract
Escherichia coli is the primary cause of urinary tract infection (UTI) in the developed world. The major factors associated with the virulence of uropathogenic E. coli (UPEC) are fimbrial adhesins, which mediate specific attachment to host receptors and trigger innate host responses. Another group of adhesins is represented by the autotransporter subgroup of proteins. The best characterized of these proteins, antigen 43 (Ag43), is a self-recognizing adhesin that is associated with cell aggregation and biofilm formation in E. coli K-12. The sequenced genome of prototype UPEC strain CFT073 contains two variant Ag43-encoding genes located on pathogenicity islands. The biological significance of both of these genes and their role in UPEC pathogenesis have not been investigated previously. Here we performed a detailed molecular characterization analysis of Ag43a (c3655) and Ag43b (c1273) from UPEC CFT073. Expression of Ag43a and Ag43b in a K-12 background revealed that they possess different functional properties. Ag43a produced a strong aggregation phenotype and promoted significant biofilm growth. Deletion mutants and strains constitutively expressing Ag43a and Ag43b were also constructed using CFT073. When these mutants were analyzed in a mouse model of UTI, Ag43a (but not Ag43b) promoted long-term persistence in the urinary bladder. Our findings demonstrate that Ag43a contributes to UPEC disease pathogenesis and reveal that there are pathogenicity-adapted variants of Ag43 with distinct virulence-related functions.
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Affiliation(s)
- Glen C Ulett
- School of Molecular and Microbial Sciences, University of Queensland, Brisbane, QLD 4072, Australia
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43
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Lim HN, van Oudenaarden A. A multistep epigenetic switch enables the stable inheritance of DNA methylation states. Nat Genet 2007; 39:269-75. [PMID: 17220888 DOI: 10.1038/ng1956] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2006] [Accepted: 12/04/2006] [Indexed: 11/09/2022]
Abstract
In many prokaryotes and eukaryotes, DNA methylation at cis-regulatory sequences determines whether gene expression is on or off. Stable inheritance of these expression states is required in bacterial pathogenesis, cancer and developmental pathways. Here we delineate the factors that control the stability of these states by using the agn43 gene in Escherichia coli as a model system. Systematic disruption of this system shows that a functional switch requires the presence of several, rarely occupied, intermediate states that separate the 'on' and 'off' states. Cells that leave the on and off state enter different intermediate states, where there is a strong bias that drives cells back to their original state. The intermediate states therefore act as buffers that prevent back and forth switching. This mechanism of generating multiple states is an alternative to feedback regulation, and its general principle should be applicable to the analysis of other epigenetic switches and the design of synthetic circuits.
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Affiliation(s)
- Han N Lim
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
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Yang HH, Morrow JB, Grasso D, Vinopal RT, Smets BF. Intestinal versus external growth conditions change the surficial properties in a collection of environmental Escherichia coli isolates. Environ Sci Technol 2006; 40:6976-82. [PMID: 17154004 DOI: 10.1021/es061100t] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Predicting the fate of microorganisms in the environment is increasingly warranted, especially for pathogenic strains. A major habitat of Escherichia coli, which encompasses commensal as well as pathogenic strains, is the gastrointestinal tract with conditions very different from the environment it encounters after shedding from the host or during cultivation in the laboratory. We developed two relevant growth conditions representative of intestinal (host-associated) and external (postshedding) environments to investigate the surficial properties and behaviors of a diverse subset of E. coli feedlot isolates. Surficial properties may determine an isolate's physical fate. A pronounced increase in cell hydrophobicity and concomitant biofilm mass formation was observed for isolates grown under external conditions. Isolates that exhibited the highest surface hydrophobicity also formed visible suspended aggregates under external conditions. Other than hydrophobicity, flagella-mediated motility was determinant in affecting E. coli biofilm formation under external conditions, with all four nonmotile E. coli isolates characterized as thin-biofilm formers. The majority (88%) of Ag43+ (outer membrane protein, antigen 43) isolates formed thick biofilms, whereas the majority (75%) of Ag43- isolates formed thin biofilms. The tested E. coli O157:H7 strain behaved differently from the environmental E. coli isolates: it displayed a low electrostatic charge, a small decrease in hydrophobicity upon shifts to external conditions, and very little biofilm formation. On the other hand, the commonly used laboratory strain E. coli K-12 displayed low hydrophobicity both intestinally and externally, but it formed significant biofilm mass under external conditions. Clearly, various E. coli strains manifest significant variability in surficial behavior. This variability is further modulated by growth conditions. The interacting strain-inherent and cultivation-dependent effects on surficial behavior may have broad consequences for the fate and ecology of pathogenic and commensal E. coli strains.
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Affiliation(s)
- Hsiao-Hui Yang
- Microbiology Program and Environmental Engineering Program, University of Connecticut, Storrs, Connecticut 06269, USA
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45
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Klemm P, Vejborg RM, Sherlock O. Self-associating autotransporters, SAATs: functional and structural similarities. Int J Med Microbiol 2006; 296:187-95. [PMID: 16600681 DOI: 10.1016/j.ijmm.2005.10.002] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2005] [Accepted: 10/27/2005] [Indexed: 10/24/2022] Open
Abstract
The autotransporter family of translocated proteins in Gram-negative bacteria all contain three structural motifs, a signal sequence, a passenger domain and a translocator domain. The autotransporters constitute a highly versatile group of proteins with respect to function, which accords with the widespread presence of these proteins. The group encompasses many important virulence factors. In Escherichia coli, a subgroup of autotransporter proteins consists of the TibA adhesin/invasin associated with some enterotoxigenic E. coli, the AIDA adhesin from diarrhea-causing E. coli and finally, the Ag43 autoaggregation factor found in the majority of E. coli strains. The three proteins exhibit approximately 25% identity at the sequence level, and are quite different with respect to size, glycosylation and processing. Nevertheless, they share some important properties: all are self-associating proteins that cause bacterial aggregation. They can also interact with each other via heterologous interactions to cause formation of mixed bacterial aggregates. Furthermore, these proteins enhance biofilm formation. Based on these properties we propose to classify them together in a group termed SAATs: self-associating autotransporters.
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Affiliation(s)
- Per Klemm
- Microbial Adhesion Group, Center of Biomedical Microbiology, Building 301, BioCentrum-DTU, Technical University of Denmark, DK-2800 Lyngby, Denmark.
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46
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Abstract
Functional interaction between bacterial surface-displayed autoaggregation proteins such as antigen 43 (Ag43) of Escherichia coli and motility organelles such as flagella has not previously been described. Here, it has been demonstrated for the first time that Ag43-mediated aggregation can inhibit bacterial motility. Ag43 overexpression produces a dominant aggregation phenotype that overrides motility in the presence of low levels of flagella. In contrast, induction of an increased flagellation state prevents Ag43-mediated aggregation. This phenomenon was observed in naturally occurring subpopulations of E. coli as phase variants expressing and not expressing Ag43 revealed contrasting motility phenotypes. The effects were shown to be part of a general mechanism because other short adhesins capable of mediating autoaggregation (AIDA-I and TibA) also impaired motility. These novel insights into the function of bacterial autoaggregation proteins suggest that a balance between these two systems, i.e. autoaggregation and flagellation, influences motility.
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Affiliation(s)
- Glen C Ulett
- School of Molecular and Microbial Sciences, University of Queensland, Brisbane, Queensland 4072, Australia
| | - Richard I Webb
- Centre for Microscopy and Microanalysis, University of Queensland, Brisbane, Queensland 4072, Australia
| | - Mark A Schembri
- School of Molecular and Microbial Sciences, University of Queensland, Brisbane, Queensland 4072, Australia
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47
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Beloin C, Michaelis K, Lindner K, Landini P, Hacker J, Ghigo JM, Dobrindt U. The transcriptional antiterminator RfaH represses biofilm formation in Escherichia coli. J Bacteriol 2006; 188:1316-31. [PMID: 16452414 PMCID: PMC1367212 DOI: 10.1128/jb.188.4.1316-1331.2006] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We investigated the influence of regulatory and pathogenicity island-associated factors (Hha, RpoS, LuxS, EvgA, RfaH, and tRNA5Leu) on biofilm formation by uropathogenic Escherichia coli (UPEC) strain 536. Only inactivation of rfaH, which encodes a transcriptional antiterminator, resulted in increased initial adhesion and biofilm formation by E. coli 536. rfaH inactivation in nonpathogenic E. coli K-12 isolate MG1655 resulted in the same phenotype. Transcriptome analysis of wild-type strain 536 and an rfaH mutant of this strain revealed that deletion of rfaH correlated with increased expression of flu orthologs. flu encodes antigen 43 (Ag43), which mediates autoaggregation and biofilm formation. We confirmed that deletion of rfaH leads to increased levels of flu and flu-like transcripts in E. coli K-12 and UPEC. Supporting the hypothesis that RfaH represses biofilm formation through reduction of the Ag43 level, the increased-biofilm phenotype of E. coli MG1655rfaH was reversed upon inactivation of flu. Deletion of the two flu orthologs, however, did not modify the behavior of mutant 536rfaH. Our results demonstrate that the strong initial adhesion and biofilm formation capacities of strain MG1655rfaH are mediated by both increased steady-state production of Ag43 and likely increased Ag43 presentation due to null rfaH-dependent lipopolysaccharide depletion. Although the roles of rfaH in the biofilm phenotype are different in UPEC strain 536 and K-12 strain MG1655, this study shows that RfaH, in addition to affecting the expression of bacterial virulence factors, also negatively controls expression and surface presentation of Ag43 and possibly another Ag43-independent factor(s) that mediates cell-cell interactions and biofilm formation.
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Affiliation(s)
- Christophe Beloin
- Institut für Molekulare Infektionsbiologie, Bayerische Julius-Maximilians-Universität Würzburg, Röntgenring 11, D-97070 Würzburg, Germany
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Sherlock O, Dobrindt U, Jensen JB, Munk Vejborg R, Klemm P. Glycosylation of the self-recognizing Escherichia coli Ag43 autotransporter protein. J Bacteriol 2006; 188:1798-807. [PMID: 16484190 PMCID: PMC1426561 DOI: 10.1128/jb.188.5.1798-1807.2006] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2005] [Accepted: 12/10/2005] [Indexed: 12/20/2022] Open
Abstract
Glycosylation is a common modulation of protein function in eukaryotes and is biologically important. However, in bacteria protein glycosylation is rare, and relatively few bacterial glycoproteins are known. In Escherichia coli only two glycoproteins have been described to date. Here we introduce a novel member to this exclusive group, namely, antigen 43 (Ag43), a self-recognizing autotransporter protein. By mass spectrometry Ag43 was demonstrated to be glycosylated by addition of heptose residues at several positions in the passenger domain. Glycosylation of Ag43 by the action of the Aah and TibC glycosyltransferases was observed in laboratory strains. Importantly, Ag43 was also found to be glycosylated in a wild-type strain, suggesting that Ag43-glycosylation may be a widespread phenomenon. Glycosylation of Ag43 does not seem to interfere with its self-associating properties. However, the glycosylated form of Ag43 enhances bacterial binding to human cell lines, whereas the nonglycosylated version of Ag43 does not to confer this property.
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Affiliation(s)
- Orla Sherlock
- Centre for Biomedical Microbiology, BioCentrum-DTU, Bldg. 301, Technical University of Denmark, DK-2800 Lyngby, Denmark
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Snyder JA, Haugen BJ, Lockatell CV, Maroncle N, Hagan EC, Johnson DE, Welch RA, Mobley HLT. Coordinate expression of fimbriae in uropathogenic Escherichia coli. Infect Immun 2005; 73:7588-96. [PMID: 16239562 PMCID: PMC1273908 DOI: 10.1128/iai.73.11.7588-7596.2005] [Citation(s) in RCA: 108] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2005] [Revised: 07/22/2005] [Accepted: 07/28/2005] [Indexed: 01/12/2023] Open
Abstract
Uropathogenic Escherichia coli is the most common etiological agent of urinary tract infections. Bacteria can often express multiple adhesins during infection in order to favor attachment to specific niches within the urinary tract. We have recently demonstrated that type 1 fimbria, a phase-variable virulence factor involved in adherence, was the most highly expressed adhesin during urinary tract infection. Here, we examine whether the expression of type 1 fimbriae can affect the expression of other adhesins. Type 1 fimbrial phase-locked mutants of E. coli strain CFT073, which harbors genes for numerous adhesins, were employed in this study. CFT073-specific DNA microarray analysis of these strains demonstrates that the expression of type 1 fimbriae coordinately affects the expression of P fimbriae in an inverse manner. This represents evidence for direct communication between genes relating to pathogenesis, perhaps to aid the sequential occupation of different urinary tract tissues. While the role of type 1 fimbriae during infection has been clear, the role of P fimbriae must be further defined to assert the relevance of coordinated regulation in vivo. Therefore, we examined the ability of P fimbrial isogenic mutants, constructed in a type 1 fimbrial-negative background, to compete in the murine urinary tract over a period of 168 h. No differences in the colonization of these mutants were observed. However, comparison of these results with previous studies suggests that inversely coordinated expression of adhesin gene clusters does occur in vivo. Interestingly, the mutant that was incapable of expressing either type 1 or P fimbriae compensated by synthesizing F1C fimbriae.
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Affiliation(s)
- Jennifer A Snyder
- Department of Microbiology and Immunology, University of Michigan Medical School, 5641 Medical Science Building II, 1150 West Medical Center Drive, Ann Arbor, MI 48109, USA
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Sherlock O, Vejborg RM, Klemm P. The TibA adhesin/invasin from enterotoxigenic Escherichia coli is self recognizing and induces bacterial aggregation and biofilm formation. Infect Immun 2005; 73:1954-63. [PMID: 15784535 PMCID: PMC1087433 DOI: 10.1128/iai.73.4.1954-1963.2005] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2004] [Revised: 10/20/2004] [Accepted: 11/22/2004] [Indexed: 11/20/2022] Open
Abstract
Escherichia coli strains are responsible for many cases of gastrointestinal disease and represent a serious health problem worldwide. An essential step in the pathogenesis of such strains involves recognition and attachment to host intestinal surfaces. TibA is a potent bacterial adhesin associated with a number of enterotoxigenic E. coli strains and mediates bacterial attachment to a variety of human cells; additionally, it promotes invasion of such cells. This adhesin is a surface-displayed autotransporter protein and belongs to the exclusive group of bacterial glycoproteins; only the glycosylated form confers binding to and invasion of mammalian cells. Here we characterized TibA and showed that it possesses self-association characteristics and can mediate autoaggregation of E. coli cells. We demonstrated that intercellular TibA-TibA interaction is responsible for bacterial autoaggregation. Also, TibA expression significantly enhances biofilm formation by E. coli on abiotic surfaces.
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Affiliation(s)
- Orla Sherlock
- Centre for Biomedical Microbiology, BioCentrum-DTU, Bldg. 301, Technical University of Denmark, DK-2800 Lyngby, Denmark
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