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Midgett CR, Talbot KM, Day JL, Munson GP, Kull FJ. Structure of the master regulator Rns reveals an inhibitor of enterotoxigenic Escherichia coli virulence regulons. Sci Rep 2021; 11:15663. [PMID: 34341412 PMCID: PMC8329261 DOI: 10.1038/s41598-021-95123-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Accepted: 07/14/2021] [Indexed: 02/07/2023] Open
Abstract
Enteric infections caused by the gram-negative bacteria enterotoxigenic Escherichia coli (ETEC), Vibrio cholerae, Shigella flexneri, and Salmonella enterica are among the most common and affect billions of people each year. These bacteria control expression of virulence factors using a network of transcriptional regulators, some of which are modulated by small molecules as has been shown for ToxT, an AraC family member from V. cholerae. In ETEC the expression of many types of adhesive pili is dependent upon the AraC family member Rns. We present here the 3 Å crystal structure of Rns and show it closely resembles ToxT. Rns crystallized as a dimer via an interface similar to that observed in other dimeric AraC's. Furthermore, the structure of Rns revealed the presence of a ligand, decanoic acid, that inhibits its activity in a manner similar to the fatty acid mediated inhibition observed for ToxT and the S. enterica homologue HilD. Together, these results support our hypothesis that fatty acids regulate virulence controlling AraC family members in a common manner across a number of enteric pathogens. Furthermore, for the first time this work identifies a small molecule capable of inhibiting the ETEC Rns regulon, providing a basis for development of therapeutics against this deadly human pathogen.
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Affiliation(s)
| | - Kacey Marie Talbot
- Department of Microbiology and Immunology, Miller School of Medicine, University of Miami, Miami, FL, USA
| | - Jessica L Day
- Department of Chemistry, Dartmouth College, Hanover, NH, USA
- Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, NH, USA
| | - George P Munson
- Department of Microbiology and Immunology, Miller School of Medicine, University of Miami, Miami, FL, USA
| | - F Jon Kull
- Department of Chemistry, Dartmouth College, Hanover, NH, USA.
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Orench-Rivera N, Kuehn MJ. Differential Packaging Into Outer Membrane Vesicles Upon Oxidative Stress Reveals a General Mechanism for Cargo Selectivity. Front Microbiol 2021; 12:561863. [PMID: 34276573 PMCID: PMC8284480 DOI: 10.3389/fmicb.2021.561863] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Accepted: 06/09/2021] [Indexed: 12/12/2022] Open
Abstract
Selective cargo packaging into bacterial extracellular vesicles has been reported and implicated in many biological processes, however, the mechanism behind the selectivity has remained largely unexplored. In this study, proteomic analysis of outer membrane (OM) and OM vesicle (OMV) fractions from enterotoxigenic E. coli revealed significant differences in protein abundance in the OMV and OM fractions for cultures shifted to oxidative stress conditions. Analysis of sequences of proteins preferentially packaged into OMVs showed that proteins with oxidizable residues were more packaged into OMVs in comparison with those retained in the membrane. In addition, the results indicated two distinct classes of OM-associated proteins were differentially packaged into OMVs as a function of peroxide treatment. Implementing a Bayesian hierarchical model, OM lipoproteins were determined to be preferentially exported during stress whereas integral OM proteins were preferentially retained in the cell. Selectivity was determined to be independent of transcriptional regulation of the proteins upon oxidative stress and was validated using randomly selected protein candidates from the different cargo classes. Based on these data, a hypothetical functional and mechanistic basis for cargo selectivity was tested using OmpA constructs. Our study reveals a basic mechanism for cargo selectivity into OMVs that may be useful for the engineering of OMVs for future biotechnological applications.
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Affiliation(s)
| | - Meta J. Kuehn
- Department of Biochemistry, Duke University Medical Center, Durham, NC, United States
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3
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van der Westhuizen WA, Theron CW, Boucher CE, Bragg RR. Regulation of outer-membrane proteins (OMPs) A and F, during hlyF-induced outer-membrane vesicle (OMV) biosynthesis. Heliyon 2019; 5:e02014. [PMID: 31312732 PMCID: PMC6610587 DOI: 10.1016/j.heliyon.2019.e02014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Revised: 06/04/2019] [Accepted: 06/26/2019] [Indexed: 01/21/2023] Open
Abstract
Background Gram-negative bacteria actively secrete outer membrane vesicles into the surrounding environment and these vesicles have been shown to play various physiological and protective roles such as carrying antibiotic-degrading enzymes and acting as decoys against host defences, therefore promoting the pathogenesis of the bacterium. It has been shown that avian pathogenic Escherichia coli species can increase vesicle biosynthesis through the acquisition of the hlyF gene but the effect this has on the cell by scavenging outer-membrane associated proteins (OmpA, OmpF) into the vesicles during vesicle release have not yet been investigated. Results Relative quantitative real-time PCR data obtained from hlyF expressing and non-expressing cells showed that during hlyF induction, ompF showed a nearly 2-fold down regulation relative to the non-expressing cells during the entire 24 hours, while ompA was expressed at the same level as the non-expressing cells during the first 8 hours of expression. At 24 hours post-hlyF expression, ompA was up-regulated 4-fold. Conclusions The regulatory effects of the newly described outer-membrane vesicle biosynthesis-related gene, hlyF, on E. coli has not previously been investigated. As hlyF-induced vesicles contain OmpA and OmpF scavenged from the bacterial outer-membrane, potential regulatory effects on the host was investigated. An increase in ompA expression and an insignificant decrease in ompF expression was observed during hlyF induction demonstrating that hlyF-related biosynthesis is not related to decreased ompA expression, which is one of the potential mechanisms discussed in literature for biosynthesis. Outer-membrane vesicle biosynthesis during hlyF over-expression could potentially be accomplished through a different mechanism(s).
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Affiliation(s)
- Wouter André van der Westhuizen
- Department of Microbial, Biochemical and Food Biotechnology, Internal Box 61, University of the Free State, P.O. Box 339, Bloemfontein, 9301, South Africa
| | - Chrispian William Theron
- Department of Microbial, Biochemical and Food Biotechnology, Internal Box 61, University of the Free State, P.O. Box 339, Bloemfontein, 9301, South Africa
| | - Charlotte Enastacia Boucher
- Department of Microbial, Biochemical and Food Biotechnology, Internal Box 61, University of the Free State, P.O. Box 339, Bloemfontein, 9301, South Africa
| | - Robert Richard Bragg
- Department of Microbial, Biochemical and Food Biotechnology, Internal Box 61, University of the Free State, P.O. Box 339, Bloemfontein, 9301, South Africa
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Lalaouna D, Eyraud A, Devinck A, Prévost K, Massé E. GcvB small RNA uses two distinct seed regions to regulate an extensive targetome. Mol Microbiol 2018; 111:473-486. [PMID: 30447071 DOI: 10.1111/mmi.14168] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/12/2018] [Indexed: 01/01/2023]
Abstract
GcvB small RNA is described as post-transcriptional regulator of 1-2% of all mRNAs in Escherichia coli and Salmonella Typhimurium. At least 24 GcvB:mRNA interactions have been validated in vivo, establishing the largest characterized sRNA targetome. By performing MS2-affinity purification coupled with RNA sequencing (MAPS) technology, we identified seven additional mRNAs negatively regulated by GcvB in E. coli. Contrary to the vast majority of previously known targets, which pair to the well-conserved GcvB R1 region, we validated four mRNAs targeted by GcvB R3 region. This indicates that base-pairing through R3 seed sequence seems relatively common. We also noticed unusual GcvB pairing sites in the coding sequence of two target mRNAs. One of these target mRNAs has a pairing site displaying a unique ACA motif, suggesting that GcvB could hijack a translational enhancer element. The second target mRNA is likely regulated via an active RNase E-mediated mRNA degradation mechanism. Remarkably, we confirmed the importance of the sRNA sponge SroC in the fine-tuning control of GcvB activity in function of growth conditions such as growth phase and nutrient availability.
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Affiliation(s)
- David Lalaouna
- Department of Biochemistry, RNA Group, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - Alex Eyraud
- Department of Biochemistry, RNA Group, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - Aurélie Devinck
- Department of Biochemistry, RNA Group, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - Karine Prévost
- Department of Biochemistry, RNA Group, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - Eric Massé
- Department of Biochemistry, RNA Group, Université de Sherbrooke, Sherbrooke, Québec, Canada
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Peng J, Miao L, Chen X, Liu P. Comparative Transcriptome Analysis of Pseudomonas putida KT2440 Revealed Its Response Mechanisms to Elevated Levels of Zinc Stress. Front Microbiol 2018; 9:1669. [PMID: 30087671 PMCID: PMC6066579 DOI: 10.3389/fmicb.2018.01669] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2018] [Accepted: 07/04/2018] [Indexed: 01/03/2023] Open
Abstract
The whole-genome transcriptional response of Pseudomonas putida KT2440 to stress-inducing concentrations of zinc was analyzed in this study by RNA sequencing to thoroughly investigate the bacterial cell response to zinc toxicity. The data revealed that different levels of zinc stress strongly affected the transcription of genes from the following categories: metal transport genes, genes involved in membrane homeostasis, oxidative-stress-responding genes, and genes associated with basic cellular metabolism. At the lowest zinc dose, only several genes associated with metal transport and membrane homeostasis were strongly influenced. At the intermediate zinc dose, transcriptional changes of genes belonging to these two categories were highly pronounced. In addition, the intermediate zinc stress produced high levels of oxidative stress, and influenced amino acid metabolism and respiratory chains of P. putida. At the highest zinc dose, the induction of genes responsible for Fe–S cluster biogenesis was the most remarkable feature. Moreover, upregulation of glyoxylate cycle was observed. In summary, the adaptation of the cell envelope, the maintenance of metal homeostasis and intracellular redox status, and the transcriptional control of metabolism are the main elements of stress response, which facilitates the survival of P. putida KT2440 in zinc-polluted environments.
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Affiliation(s)
- Jun Peng
- College of Biological and Pharmaceutical Engineering, Wuhan Polytechnic University, Wuhan, China
| | - Lihong Miao
- College of Biological and Pharmaceutical Engineering, Wuhan Polytechnic University, Wuhan, China
| | - Xi Chen
- Wuhan Institute of Virology, Chinese Academy of Science, Wuhan, China
| | - Pulin Liu
- College of Biological and Pharmaceutical Engineering, Wuhan Polytechnic University, Wuhan, China
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Hashemzehi R, Doosti A, Kargar M, Jaafarinia M. Cloning and expression of nlpA gene as DNA vaccine candidate against Acinetobacter baumannii. Mol Biol Rep 2018; 45:395-401. [DOI: 10.1007/s11033-018-4167-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2017] [Accepted: 03/16/2018] [Indexed: 01/29/2023]
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Verma R, Rojas TCG, Maluta RP, Leite JL, Nakazato G, de Silveira WD. Role of hypothetical protein YicS in the pathogenicity of Avian Pathogenic Escherichia coli in vivo and in vitro. Microbiol Res 2018; 214:28-36. [PMID: 30031479 DOI: 10.1016/j.micres.2018.05.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 05/04/2018] [Accepted: 05/12/2018] [Indexed: 10/16/2022]
Abstract
Avian Pathogenic Escherichia coli (APEC) strains belong to the extra-intestinal pathogenic group of E. coli (ExPEC) that causes colibacillosis in poultry. A variety of putative virulence factors of APEC are recognized as potent causes of pathogenicity, the mechanisms underlying their pathogenicity are still not fully understood. The role of yicS in the virulence of pathogenic E. coli is still unclear. Thus, yicS may be related to biofilm formation, which in some bacteria plays a role in pathogenicity. Therefore, the fact that this gene appears to be under positive selection pressure suggests that yicS may be associated with the pathogenicity of APEC. To better understand the role of yicS protein in APEC biological characteristics and pathogenicity, we deleted yicS in an APEC Swollen Head Syndrome strain (APEC strain SCI-07) and studied its effects by comparing wild type and isogenic mutants through comprehensive in vitro and in vivo assays. We demonstrated that yicS plays a role in pathogenicity of APEC. We suggest that the yicS gene, which encodes an exporter protein, has a significant role in biofilm formation, motility, invasion of CEC-32 and Hep-2 cells and APEC pathogenicity in a day-old chick model.
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Affiliation(s)
- Renu Verma
- Department of Genetics, Evolution and Bioagents, Institute of Biology, PO Box 6109, State University of Campinas-UNICAMP, 13083-875, Campinas, SP, Brazil.
| | - Thaís Cabrera Galvão Rojas
- Department of Genetics, Evolution and Bioagents, Institute of Biology, PO Box 6109, State University of Campinas-UNICAMP, 13083-875, Campinas, SP, Brazil
| | - Renato Pariz Maluta
- Department of Genetics, Evolution and Bioagents, Institute of Biology, PO Box 6109, State University of Campinas-UNICAMP, 13083-875, Campinas, SP, Brazil
| | - Janaína Luisa Leite
- Department of Genetics, Evolution and Bioagents, Institute of Biology, PO Box 6109, State University of Campinas-UNICAMP, 13083-875, Campinas, SP, Brazil
| | - Gerson Nakazato
- Department of Microbiology, Biological Science Center, Institute of Biology, University of Londrina-UEL, 86055-990, Londrina, PR, Brazil
| | - Wanderley Dias de Silveira
- Department of Genetics, Evolution and Bioagents, Institute of Biology, PO Box 6109, State University of Campinas-UNICAMP, 13083-875, Campinas, SP, Brazil.
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8
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Yu YJ, Wang XH, Fan GC. Versatile effects of bacterium-released membrane vesicles on mammalian cells and infectious/inflammatory diseases. Acta Pharmacol Sin 2018; 39:514-533. [PMID: 28858295 PMCID: PMC5888691 DOI: 10.1038/aps.2017.82] [Citation(s) in RCA: 87] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Accepted: 05/10/2017] [Indexed: 01/18/2023] Open
Abstract
Gram-negative bacterium-released outer-membrane vesicles (OMVs) and Gram-positive bacterium-released membrane vesicles (MVs) share significant similarities with mammalian cell-derived MVs (eg, microvesicles and exosomes) in terms of structure and their biological activities. Recent studies have revealed that bacterial OMVs/MVs could (1) interact with immune cells to regulate inflammatory responses, (2) transport virulence factors (eg, enzymes, DNA and small RNAs) to host cells and result in cell injury, (3) enhance barrier function by stimulating the expression of tight junction proteins in intestinal epithelial cells, (4) upregulate the expression of endothelial cell adhesion molecules, and (5) serve as natural nanocarriers for immunogenic antigens, enzyme support and drug delivery. In addition, OMVs/MVs can enter the systemic circulation and induce a variety of immunological and metabolic responses. This review highlights the recent advances in the understanding of OMV/MV biogenesis and their compositional remodeling. In addition, interactions between OMVs/MVs and various types of mammalian cells (ie, immune cells, epithelial cells, and endothelial cells) and their pathological/preventive effects on infectious/inflammatory diseases are summarized. Finally, methods for engineering OMVs/MVs and their therapeutic potential are discussed.
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Affiliation(s)
- You-jiang Yu
- Medical College of Yangzhou Polytechnic College, Yangzhou 225009, China
| | - Xiao-hong Wang
- Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, OH 45267, USA
| | - Guo-Chang Fan
- Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, OH 45267, USA
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9
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Hodson C, Yang J, Hocking DM, Azzopardi K, Chen Q, Holien JK, Parker MW, Tauschek M, Robins-Browne RM. Control of Virulence Gene Expression by the Master Regulator, CfaD, in the Prototypical Enterotoxigenic Escherichia coli Strain, H10407. Front Microbiol 2017; 8:1525. [PMID: 28848532 PMCID: PMC5554520 DOI: 10.3389/fmicb.2017.01525] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Accepted: 07/28/2017] [Indexed: 12/24/2022] Open
Abstract
Enterotoxigenic Escherichia coli (ETEC) is the most common bacterial cause of diarrhea in children in developing countries, as well as in travelers to these countries. To cause disease, ETEC needs to produce a series of virulence proteins including enterotoxins, colonization factors and secretion pathways, which enable this pathogen to colonize the human small intestine and deliver enterotoxins to epithelial cells. Previously, a number of studies have demonstrated that CfaD, an AraC-like transcriptional regulator, plays a key role in virulence gene expression by ETEC. In this study, we carried out a transcriptomic analysis of ETEC strain, H10407, grown under different conditions, and determined the complete set of genes that are regulated by CfaD. In this way, we identified a number of new target genes, including rnr-1, rnr-2, etpBAC, agn43, flu, traM and ETEC_3214, whose expression is strongly activated by CfaD. Using promoter-lacZ reporters, primer extension and electrophoretic mobility shift assays, we characterized the CfaD-mediated activation of several selected target promoters. We also showed that the gut-associated environmental signal, sodium bicarbonate, stimulates CfaD-mediated upregulation of its virulence target operons. Finally, we screened a commercial small molecule library and identified a compound (CH-1) that specifically inhibited the regulatory function of CfaD, and by 2-D analoging, we identified a second inhibitor (CH-2) with greater potency.
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Affiliation(s)
- Carla Hodson
- Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, The University of Melbourne, ParkvilleVIC, Australia
| | - Ji Yang
- Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, The University of Melbourne, ParkvilleVIC, Australia
| | - Dianna M Hocking
- Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, The University of Melbourne, ParkvilleVIC, Australia
| | - Kristy Azzopardi
- Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, The University of Melbourne, ParkvilleVIC, Australia.,Murdoch Childrens Research Institute, The Royal Children's Hospital, ParkvilleVIC, Australia
| | - Qianyu Chen
- Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, The University of Melbourne, ParkvilleVIC, Australia
| | - Jessica K Holien
- Australian Cancer Research Foundation Rational Drug Discovery Centre, St. Vincent's Institute of Medical Research, FitzroyVIC, Australia
| | - Michael W Parker
- Australian Cancer Research Foundation Rational Drug Discovery Centre, St. Vincent's Institute of Medical Research, FitzroyVIC, Australia.,Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, ParkvilleVIC, Australia
| | - Marija Tauschek
- Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, The University of Melbourne, ParkvilleVIC, Australia
| | - Roy M Robins-Browne
- Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, The University of Melbourne, ParkvilleVIC, Australia.,Murdoch Childrens Research Institute, The Royal Children's Hospital, ParkvilleVIC, Australia
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10
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The Virulence Regulator Rns Activates the Expression of CS14 Pili. Genes (Basel) 2016; 7:genes7120120. [PMID: 27941642 PMCID: PMC5192496 DOI: 10.3390/genes7120120] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 11/28/2016] [Accepted: 11/30/2016] [Indexed: 11/16/2022] Open
Abstract
Although many viral and bacterial pathogens cause diarrhea, enterotoxigenic E. coli (ETEC) is one of the most frequently encountered in impoverished regions where it is estimated to kill between 300,000 and 700,000 children and infants annually. Critical ETEC virulence factors include pili which mediate the attachment of the pathogen to receptors in the intestinal lumen. In this study we show that the ETEC virulence regulator Rns positively regulates the expression of CS14 pili. Three Rns binding sites were identified upstream of the CS14 pilus promoter centered at -34.5, -80.5, and -155.5 relative to the Rns-dependent transcription start site. Mutagenesis of the promoter proximal site significantly decreased expression from the CS14 promoter. In contrast, the contribution of Rns bound at the promoter distal site was negligible and largely masked by occupancy of the promoter proximal site. Unexpectedly, Rns bound at the site centered at -80.5 had a slight but statistically significant inhibitory effect upon the pilin promoter. Nevertheless, this weak inhibitory effect was not sufficient to overcome the substantial promoter activation from Rns bound to the promoter proximal site. Thus, CS14 pili belong to a group of pili that depend upon Rns for their expression.
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11
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Evolutionary adaptation of an AraC-like regulatory protein in Citrobacter rodentium and Escherichia species. Infect Immun 2015; 83:1384-95. [PMID: 25624355 DOI: 10.1128/iai.02697-14] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The evolution of pathogenic bacteria is a multifaceted and complex process, which is strongly influenced by the horizontal acquisition of genetic elements and their subsequent expression in their new hosts. A well-studied example is the RegA regulon of the enteric pathogen Citrobacter rodentium. The RegA regulatory protein is a member of the AraC/XylS superfamily, which coordinates the expression of a gene repertoire that is necessary for full pathogenicity of this murine pathogen. Upon stimulation by an exogenous, gut-associated signal, namely, bicarbonate ions, RegA activates the expression of a series of genes, including virulence factors, such as autotransporters, fimbriae, a dispersin-like protein, and the grlRA operon on the locus of enterocyte effacement pathogenicity island. Interestingly, the genes encoding RegA homologues are distributed across the genus Escherichia, encompassing pathogenic and nonpathogenic subtypes. In this study, we carried out a series of bioinformatic, transcriptional, and functional analyses of the RegA regulons of these bacteria. Our results demonstrated that regA has been horizontally transferred to Escherichia spp. and C. rodentium. Comparative studies of two RegA homologues, namely, those from C. rodentium and E. coli SMS-3-5, a multiresistant environmental strain of E. coli, showed that the two regulators acted similarly in vitro but differed in terms of their abilities to activate the virulence of C. rodentium in vivo, which evidently was due to their differential activation of grlRA. Our data indicate that RegA from C. rodentium has strain-specific adaptations that facilitate infection of its murine host. These findings shed new light on the development of virulence by C. rodentium and on the evolution of virulence-regulatory genes of bacterial pathogens in general.
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Kulkarni HM, Jagannadham MV. Biogenesis and multifaceted roles of outer membrane vesicles from Gram-negative bacteria. Microbiology (Reading) 2014; 160:2109-2121. [DOI: 10.1099/mic.0.079400-0] [Citation(s) in RCA: 118] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Outer membrane vesicles (OMVs) released from Gram-negative bacteria consist of lipids, proteins, lipopolysaccharides and other molecules. OMVs are associated with several biological functions such as horizontal gene transfer, intracellular and intercellular communication, transfer of contents to host cells, and eliciting an immune response in host cells. Although hypotheses have been made concerning the mechanism of biogenesis of these vesicles, research on OMV formation is far from complete. The roles of outer membrane components, bacterial quorum sensing molecules and some specific proteins in OMV biogenesis have been studied. This review discusses the different models that have been proposed for OMV biogenesis, along with details of the biological functions of OMVs and the likely scope of future research.
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Affiliation(s)
- Heramb M. Kulkarni
- CSIR – Centre for Cellular and Molecular Biology, Tarnaka, Hyderabad-500007, India
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13
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Abstract
Enterotoxigenic Escherichia coli is frequently associated with travelers' diarrhea and is a leading cause of infant and childhood mortality in developing countries. Disease is dependent upon the orchestrated expression of enterotoxins, flexible adhesive pili, and other virulence factors. Both the heat-labile (LT) and heat-stable (ST-H) enterotoxins are regulated at the level of transcription by cAMP-receptor protein which represses the expression of LT while activating expression of ST-H. The expression of many different serotypes of adhesive pili is regulated by Rns, a member of the AraC family that represents a subgroup of conserved virulence regulators from several enteric pathogens. These Rns-like regulators recognize similar DNA binding sites, and a compiled sequence logo suggests they may bind DNA through both major and minor groove interactions. These regulators are also tempting targets for novel therapeutics because they play pivotal roles during infection. To that end, high-throughput screens have begun to identify compounds that inhibit the activity of these regulators, predominately by interfering with DNA binding.
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Affiliation(s)
- George P Munson
- Department of Microbiology and Immunology, University of Miami Miller School of Medicine, P.O. Box 016960 (R-138), Miami, FL, 33101, USA,
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14
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Hong S, Cha I, Kim NO, Seo JB, Kim SY, Kim JH, Chung GT, Jeon B, Kang YH. Comparative proteomic label-free analysis of Campylobacter jejuni NCTC 11168 cultured with porcine mucin. Foodborne Pathog Dis 2014; 11:240-7. [PMID: 24552179 DOI: 10.1089/fpd.2013.1596] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Campylobacter jejuni is a major gastrointestinal pathogen in humans. Poultry is a primary reservoir for C. jejuni, and C. jejuni appears to be highly adapted to the gastrointestinal tracts of avian species. We determined the protein expression profiles of C. jejuni NCTC 11168 cultured in medium containing porcine mucin. Differentially expressed proteins in the presence and absence of porcine mucin were identified using the label-free method. We identified 52 proteins with expression that was either upregulated (32 proteins) or downregulated (20 proteins) by porcine mucin. These proteins are involved in diverse cellular functions, such as motility, cell wall synthesis, iron transport, energy production, and amino acid metabolism. In particular, the upregulated proteins were involved in chemotaxis (CheV and CetA), motility (FlaA), colonization and adherence (CadF, FrdA, CfrA, MapA, and HydA), and stress tolerance (TrxB and ClpB). These results suggest that C. jejuni changes its protein expression in response to porcine mucin and that this change in expression may contribute to host adaptation of C. jejuni NCTC 11168.
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Affiliation(s)
- Sahyun Hong
- 1 Division of Enteric Diseases, Center for Infectious Diseases, Korea National Institute of Health , Osong-eup, Chungcheongbuk-do, Republic of Korea
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15
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Role of the biofilm master regulator CsgD in cross-regulation between biofilm formation and flagellar synthesis. J Bacteriol 2011; 193:2587-97. [PMID: 21421764 DOI: 10.1128/jb.01468-10] [Citation(s) in RCA: 124] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
CsgD, the master regulator of biofilm formation, activates the synthesis of curli fimbriae and extracellular polysaccharides in Escherichia coli. To obtain insights into its regulatory role, we have identified a total of 20 novel regulation target genes on the E. coli genome by using chromatin immunoprecipitation (ChIP)-on-chip analysis with a high-density DNA microarray. By DNase I footprinting, the consensus CsgD-binding sequence predicted from a total of 18 target sites was found to include AAAAGNG(N(2))AAAWW. After a promoter-lacZ fusion assay, the CsgD targets were classified into two groups: group I genes, such as fliE and yhbT, are repressed by CsgD, while group II genes, including yccT and adrA, are activated by CsgD. The fliE and fliEFGH operons for flagellum formation are directly repressed by CsgD, while CsgD activates the adrA gene, which encodes an enzyme for synthesis of cyclic di-GMP, a bacterial second messenger, which in turn inhibits flagellum production and rotation. Taking these findings together, we propose that the cell motility for planktonic growth is repressed by CsgD, thereby promoting the switch to biofilm formation.
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The tib adherence locus of enterotoxigenic Escherichia coli is regulated by cyclic AMP receptor protein. J Bacteriol 2011; 193:1369-76. [PMID: 21216994 DOI: 10.1128/jb.00288-10] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Enterotoxigenic Escherichia coli (ETEC) is a Gram-negative enteric pathogen that causes profuse watery diarrhea through the elaboration of heat-labile and/or heat-stable toxins. Virulence is also dependent upon the expression of adhesive pili and afimbrial adhesins that allow the pathogen to adhere to the intestinal epithelium or mucosa. Both types of enterotoxins are regulated at the level of transcription by cyclic AMP (cAMP) receptor protein (CRP). To further our understanding of virulence gene regulation, an in silico approach was used to identify putative CRP binding sites in the genome of H10407 (O78:H11), an ETEC strain that was originally isolated from the stool of a Bangledeshi patient with cholera-like symptoms circa 1971. One of the predicted binding sites was located within an intergenic region upstream of tibDBCA. TibA is an autotransporter and afimbrial adhesin that is glycosylated by TibC. Expression of the TibA glycoprotein was abolished in an H10407 crp mutant and restored when crp was provided in trans. TibA-dependent aggregation was also abolished in a cyaA::kan strain and restored by addition of exogenous cAMP to the growth medium. DNase I footprinting confirmed that the predicted site upstream of tibDBCA is bound by CRP. Point mutations within the CRP binding site were found to abolish or significantly impair CRP-dependent activation of the tibDB promoter. Thus, these studies demonstrate that CRP positively regulates the expression of the glycosylated afimbrial adhesin TibA through occupancy of a binding site within tibDBp.
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Mahon V, Smyth CJ, Smith SGJ. Mutagenesis of the Rns regulator of enterotoxigenic Escherichia coli reveals roles for a linker sequence and two helix-turn-helix motifs. MICROBIOLOGY-SGM 2010; 156:2796-2806. [PMID: 20507887 DOI: 10.1099/mic.0.038521-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The pathogenesis of diarrhoeal disease due to human enterotoxigenic Escherichia coli absolutely requires the expression of fimbriae. The expression of CS1 fimbriae is positively regulated by the AraC-like protein Rns. AraC-like proteins are DNA-binding proteins that typically contain two helix-turn-helix (HTH) motifs. A program of pentapeptide insertion mutagenesis of the Rns protein was performed, and this revealed that both HTH motifs are required by Rns to positively regulate CS1 fimbrial gene expression. Intriguingly, a pentapeptide insertion after amino acid C102 reduced the ability of Rns to transactivate CS1 fimbrial expression. The structure of Rns in this vicinity (NACRS) was predicted to be disordered and thus might act as a flexible linker. This hypothesis was confirmed by deletion of this amino acid sequence from the Rns protein; a truncated protein that lacked this sequence was no longer functional. Strikingly, this sequence could be functionally substituted in vivo and in vitro by a flexible seven amino acid sequence from another E. coli AraC-like protein RhaS. Our data indicate that HTH motifs and a flexible sequence are required by Rns for maximal activation of fimbrial gene expression.
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Affiliation(s)
- Vivienne Mahon
- Department of Clinical Microbiology, School of Medicine, Trinity College Dublin, St James's Hospital, Dublin 8, Ireland.,Institute of Molecular Medicine, Trinity Centre, Trinity College Dublin, St James's Hospital, Dublin 8, Ireland.,Department of Microbiology, School of Genetics and Microbiology, Moyne Institute of Preventive Medicine, Trinity College Dublin, University of Dublin, Dublin 2, Ireland
| | - Cyril J Smyth
- Department of Microbiology, School of Genetics and Microbiology, Moyne Institute of Preventive Medicine, Trinity College Dublin, University of Dublin, Dublin 2, Ireland
| | - Stephen G J Smith
- Institute of Molecular Medicine, Trinity Centre, Trinity College Dublin, St James's Hospital, Dublin 8, Ireland.,Department of Microbiology, School of Genetics and Microbiology, Moyne Institute of Preventive Medicine, Trinity College Dublin, University of Dublin, Dublin 2, Ireland.,Department of Clinical Microbiology, School of Medicine, Trinity College Dublin, St James's Hospital, Dublin 8, Ireland
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Abstract
Enterotoxigenic Escherichia coli is a major cause of acute diarrheal illness worldwide and is responsible for high infant and child mortality rates in developing nations. Two types of enterotoxins, one heat labile and the other heat stable, are known to cause diarrhea. The expression of soluble heat-labile toxin is subject to catabolite (glucose) activation, and three binding sites for cAMP receptor protein (CRP or CAP) were identified upstream and within the toxin promoter by DNase I footprinting. One CRP operator is centered at -31.5, thus encompassing the promoter's -35 hexamer. Potassium permanganate footprinting revealed that the occupancy of this operator prevents RNA polymerase from forming an open complex in vitro. However, the operator centered at -31.5 is not sufficient for full repression in vivo because the deletion of the other two CRP binding sites partially relieved the CRP-dependent repression of the heat-labile toxin promoter. In contrast to heat-labile toxin, CRP positively regulates the expression of heat-stable toxin. Thus, the conditions for the optimal expression of one enterotoxin limit the expression of the other. Since glucose inhibits the activity of CRP by suppressing the pathogen's synthesis of cyclic AMP (cAMP), the concentration of glucose in the lumen of the small intestine may determine which enterotoxin is maximally expressed. In addition, our results suggest that the host may also modulate enterotoxin expression because cells intoxicated with heat-labile toxin overproduce and release cAMP.
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Bodero MD, Harden EA, Munson GP. Transcriptional regulation of subclass 5b fimbriae. BMC Microbiol 2008; 8:180. [PMID: 18854044 PMCID: PMC2579436 DOI: 10.1186/1471-2180-8-180] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2008] [Accepted: 10/14/2008] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Enterotoxigenic Escherichia coli (ETEC) is a major cause of infant and child mortality in developing countries. This enteric pathogen causes profuse watery diarrhea by elaborating one or more enterotoxins that intoxicate eukaryotic cells and ultimately leads to a loss of water to the intestinal lumen. Virulence is also dependent upon fimbrial adhesins that facilitate colonization of the small intestine. RESULTS The expression of CS1 fimbriae is positively regulated by Rns, a member of the AraC/XylS superfamily of transcriptional regulators. Based on fimbrial protein homology, CS1 fimbriae have been categorized as subclass 5b along with CS17, CS19, and PCFO71 fimbriae. In this study we show that Rns positively regulates the expression of these other subclass 5b members. DNase I footprinting revealed a Rns binding site adjacent to the -35 hexamer of each fimbrial promoter. The CS17 and PCFO71 fimbrial promoters carry a second Rns binding site centered at -109.5, relative to the Rns-dependent transcription start site. This second binding site is centered at -108.5 for the CS19 promoter. Mutagenesis of either site reduced Rns-dependent transcription from each promoter indicating that the molecules bound to these sites apparently function independently of one another, with each having an additive effect upon fimbrial promoter activation. CONCLUSION This study demonstrates that the ETEC virulence regulator Rns is required for the expression of all known 5b fimbriae. Since Rns is also known to control the expression of additional ETEC fimbriae, including those within subclasses 5a and 5c, the inactivation or inhibition of Rns could be an effective strategy to prevent ETEC infections.
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Affiliation(s)
- Maria D Bodero
- Department of Microbiology and Immunology, University of Miami Miller School of Medicine, Miami, FL 33101, USA.
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Muela A, Seco C, Camafeita E, Arana I, Orruño M, López JA, Barcina I. Changes in Escherichia coli outer membrane subproteome under environmental conditions inducing the viable but nonculturable state. FEMS Microbiol Ecol 2008; 64:28-36. [DOI: 10.1111/j.1574-6941.2008.00453.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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21
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Residues near the amino terminus of Rns are essential for positive autoregulation and DNA binding. J Bacteriol 2008; 190:2279-85. [PMID: 18223083 DOI: 10.1128/jb.01705-07] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Most members of the AraC/XylS family contain a conserved carboxy-terminal DNA binding domain and a less conserved amino-terminal domain involved in binding small-molecule effectors and dimerization. However, there is no evidence that Rns, a regulator of enterotoxigenic Escherichia coli virulence genes, responds to an effector ligand, and in this study we found that the amino-terminal domain of Rns does not form homodimers in vivo. Exposure of Rns to the chemical cross-linker glutaraldehyde revealed that the full-length protein is also a monomer in vitro. Nevertheless, deletion analysis of Rns demonstrated that the first 60 amino acids of the protein are essential for the activation and repression of Rns-regulated promoters in vivo. Amino-terminal truncation of Rns abolished DNA binding in vitro, and two randomly generated mutations, I14T and N16D, that independently abolished Rns autoregulation were isolated. Further analysis of these mutations revealed that they have disparate effects at other Rns-regulated promoters and suggest that they may be involved in an interaction with the carboxy-terminal domain of Rns. Thus, evolution may have preserved the amino terminus of Rns because it is essential for the regulator's activity even though it apparently lacks the two functions, dimerization and ligand binding, usually associated with the amino-terminal domains of AraC/XylS family members.
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Joshi MV, Bignell DRD, Johnson EG, Sparks JP, Gibson DM, Loria R. The AraC/XylS regulator TxtR modulates thaxtomin biosynthesis and virulence in Streptomyces scabies. Mol Microbiol 2007; 66:633-42. [PMID: 17919290 DOI: 10.1111/j.1365-2958.2007.05942.x] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Streptomyces scabies is the best studied of those streptomycetes that cause an economically important disease known as potato scab. The phytotoxin thaxtomin is made exclusively by these pathogens and is required for virulence. Here we describe regulation of thaxtomin biosynthesis by TxtR, a member of the AraC/XylS family of transcriptional regulators. The txtR gene is imbedded in the thaxtomin biosynthetic pathway and is located on a conserved pathogenicity island in S. scabies, S. turgidiscabies and S. acidiscabies. Thaxtomin biosynthesis was abolished and virulence was almost eliminated in the txtR deletion mutant of S. scabies 87.22. Accumulation of thaxtomin biosynthetic gene (txtA, txtB, txtC, nos) transcripts was reduced compared with the wild-type S. scabies 87.22. NOS-dependent nitric oxide production by S. scabies was also reduced in the mutant. The TxtR protein bound cellobiose, an inducer of thaxtomin production, and transcription of txtR and thaxtomin biosynthetic genes was upregulated in response to cellobiose. TxtR is the first example of an AraC/XylS family protein regulated by cellobiose. Together, these data suggest that cellobiose, the smallest oligomer of cellulose, may signal the availability of expanding plant tissue, which is the site of action of thaxtomin.
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Affiliation(s)
- Madhumita V Joshi
- Department of Plant Pathology, Cornell University, Ithaca, NY 14853-5904, USA
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Pilonieta MC, Bodero MD, Munson GP. CfaD-dependent expression of a novel extracytoplasmic protein from enterotoxigenic Escherichia coli. J Bacteriol 2007; 189:5060-7. [PMID: 17496090 PMCID: PMC1951884 DOI: 10.1128/jb.00131-07] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
H10407 is a strain of enterotoxigenic Escherichia coli (ETEC) that utilizes CFA/I pili to adhere to surfaces of the small intestine, where it elaborates toxins that cause profuse watery diarrhea in humans. Expression of the CFA/I pilus is positively regulated at the level of transcription by CfaD, a member of the AraC/XylS family. DNase I footprinting revealed that the activator has two binding sites upstream of the pilus promoter cfaAp. One site extends from positions -23 to -56, and the other extends from positions -73 to -103 (numbering relative to the transcription start site of cfaAp). Additional CfaD binding sites were predicted within the genome of H10407 by computational analysis. Two of these sites lie upstream of a previously uncharacterized gene, cexE. In vitro DNase I footprinting confirmed that both sites are genuine binding sites, and cexEp::lacZ reporters demonstrated that CfaD is required for the expression of cexE in vivo. The amino terminus of CexE contains a secretory signal peptide that is removed during translocation across the cytoplasmic membrane through the general secretory pathway. These studies suggest that CexE may be a novel ETEC virulence factor because its expression is controlled by the virulence regulator CfaD, and its distribution is restricted to ETEC.
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MESH Headings
- Antigens, Bacterial/genetics
- Antigens, Bacterial/physiology
- Base Sequence
- Binding Sites
- Biological Transport
- Cytoplasm/metabolism
- DNA Footprinting
- DNA-Binding Proteins/genetics
- DNA-Binding Proteins/physiology
- Electrophoresis, Polyacrylamide Gel
- Enterotoxigenic Escherichia coli/genetics
- Enterotoxigenic Escherichia coli/metabolism
- Enterotoxigenic Escherichia coli/pathogenicity
- Escherichia coli Proteins/genetics
- Escherichia coli Proteins/metabolism
- Escherichia coli Proteins/physiology
- Fimbriae Proteins/genetics
- Fimbriae Proteins/metabolism
- Fimbriae, Bacterial/genetics
- Fimbriae, Bacterial/metabolism
- Fimbriae, Bacterial/physiology
- Gene Expression Regulation, Bacterial
- Molecular Sequence Data
- Promoter Regions, Genetic
- Sequence Homology, Nucleic Acid
- Transcription, Genetic
- Virulence/genetics
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Affiliation(s)
- M Carolina Pilonieta
- Department of Microbiology and Immunology, University of Miami Miller School of Medicine, P.O. Box 016960 (R-138), Miami, FL 33101, USA
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