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De la Cruz MA, Ruiz-Tagle A, Ares MA, Pacheco S, Yáñez JA, Cedillo L, Torres J, Girón JA. The expression of Longus type 4 pilus of enterotoxigenic Escherichia coli is regulated by LngR and LngS and by H-NS, CpxR and CRP global regulators. Environ Microbiol 2017; 19:1761-1775. [PMID: 27943535 DOI: 10.1111/1462-2920.13644] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Revised: 11/30/2016] [Accepted: 12/04/2016] [Indexed: 12/31/2022]
Abstract
Enterotoxigenic Escherichia coli produces a long type 4 pilus called Longus. The regulatory elements and the environmental signals controlling the expression of Longus-encoding genes are unknown. We identified two genes lngR and lngS in the Longus operon, whose predicted products share homology with transcriptional regulators. Isogenic lngR and lngS mutants were considerably affected in transcription of lngA pilin gene. The expression of lngA, lngR and lngS genes was optimally expressed at 37°C at pH 7.5. The presence of glucose and sodium chloride had a positive effect on Longus expression. The presence of divalent ions, particularly calcium, appears to be an important stimulus for Longus production. In addition, we studied H-NS, CpxR and CRP global regulators, on Longus expression. The response regulator CpxR appears to function as a positive regulator of lng genes as the cpxR mutant showed reduced levels of lngRSA expression. In contrast, H-NS and CRP function as negative regulators since expression of lngA was up-regulated in isogenic hns and crp mutants. H-NS and CRP were required for salt- and glucose-mediated regulation of Longus. Our data suggest the existence of a complex regulatory network controlling Longus expression, involving both local and global regulators in response to different environmental signals.
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Affiliation(s)
- Miguel A De la Cruz
- Unidad de Investigación Médica en Enfermedades Infecciosas y Parasitarias, Hospital de Pediatría, Centro Médico Nacional Siglo XXI IMSS, Mexico City, Mexico
| | | | - Miguel A Ares
- Unidad de Investigación Médica en Enfermedades Infecciosas y Parasitarias, Hospital de Pediatría, Centro Médico Nacional Siglo XXI IMSS, Mexico City, Mexico
| | - Sabino Pacheco
- Departamento de Microbiología Molecular, Instituto de Biotecnología UNAM, Cuernavaca, Mexico
| | - Jorge A Yáñez
- Facultad de Estomatología, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico
| | - Lilia Cedillo
- Centro de Detección Biomolecular, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico
| | - Javier Torres
- Unidad de Investigación Médica en Enfermedades Infecciosas y Parasitarias, Hospital de Pediatría, Centro Médico Nacional Siglo XXI IMSS, Mexico City, Mexico
| | - Jorge A Girón
- Centro de Detección Biomolecular, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico.,Department of Pediatrics, University of Virginia, Charlottesville, VA, 22908, USA
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Del Canto F, O'Ryan M, Pardo M, Torres A, Gutiérrez D, Cádiz L, Valdés R, Mansilla A, Martínez R, Hernández D, Caro B, Levine MM, Rasko DA, Hill CM, Pop M, Stine OC, Vidal R. Chaperone-Usher Pili Loci of Colonization Factor-Negative Human Enterotoxigenic Escherichia coli. Front Cell Infect Microbiol 2017; 6:200. [PMID: 28111618 PMCID: PMC5216030 DOI: 10.3389/fcimb.2016.00200] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Accepted: 12/14/2016] [Indexed: 01/05/2023] Open
Abstract
Enterotoxigenic Escherichia coli (ETEC) is one of the most common causes of diarrhea worldwide. Among the 25 different ETEC adhesins, 22 are known as "colonization factors" (CFs), of which 17 are assembled by the chaperone-usher (CU) mechanism. Currently, there is no preventive therapy against ETEC, and CFs have been proposed as components for vaccine development. However, studies of diarrhea-causing ETEC strains worldwide indicate that between 15 and 50% of these are negative for known CFs, hindering the selection of the most widespread structures and suggesting that unknown adhesins remain to be identified. Here, we report the result of a comprehensive analysis of 35 draft genomes of ETEC strains which do not carry known adhesin genes; our goal was to find new CU pili loci. The phylogenetic profiles and serogroups of these strains were highly diverse, a majority of which produced only the heat-labile toxin. We identified 10 pili loci belonging to CU families β (1 locus), γ2 (7 loci), κ (1 locus), and π (1 locus), all of which contained the required number of open reading frames (ORFs) to encode functional structures. Three loci were variants of previously-known clusters, three had been only-partially described, and four are novel loci. Intra-loci genetic variability identified would allow the synthesis of up to 14 different structures. Clusters of putative γ2-CU pili were most common (23 strains), followed by putative β-CU pili (12 strains), which have not yet been fully characterized. Overall, our findings significantly increase the number of ETEC adhesion genes associated with human infections.
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Affiliation(s)
- Felipe Del Canto
- Programa de Microbiología y Micología, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile Santiago, Chile
| | - Miguel O'Ryan
- Programa de Microbiología y Micología, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile Santiago, Chile
| | - Mirka Pardo
- Programa de Microbiología y Micología, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile Santiago, Chile
| | - Alexia Torres
- Programa de Microbiología y Micología, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile Santiago, Chile
| | - Daniela Gutiérrez
- Programa de Microbiología y Micología, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile Santiago, Chile
| | - Leandro Cádiz
- Programa de Microbiología y Micología, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile Santiago, Chile
| | - Raul Valdés
- Programa de Microbiología y Micología, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de ChileSantiago, Chile; Facultad de Química y Biología, Universidad de Santiago de ChileSantiago, Chile
| | - Aquiles Mansilla
- Programa de Microbiología y Micología, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile Santiago, Chile
| | - Rodrigo Martínez
- Programa de Microbiología y Micología, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile Santiago, Chile
| | - Daniela Hernández
- Programa de Microbiología y Micología, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile Santiago, Chile
| | - Benjamin Caro
- Programa de Microbiología y Micología, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile Santiago, Chile
| | - Myron M Levine
- Center for Vaccine Development, University of Maryland School of Medicine Baltimore, MD, USA
| | - David A Rasko
- Department of Microbiology and Immunology, Institute for Genome Sciences, University of Maryland School of Medicine Baltimore, MD, USA
| | - Christopher M Hill
- Center for Bioinformatics and Computational Biology, University of Maryland Institute for Advanced Computer Studies College Park, MD, USA
| | - Mihai Pop
- Center for Bioinformatics and Computational Biology, University of Maryland Institute for Advanced Computer Studies College Park, MD, USA
| | - O Colin Stine
- Department of Epidemiology and Public Health, University of Maryland School of Medicine Baltimore, MD, USA
| | - Roberto Vidal
- Programa de Microbiología y Micología, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile Santiago, Chile
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Walsh SI, Craney A, Romesberg FE. Not just an antibiotic target: Exploring the role of type I signal peptidase in bacterial virulence. Bioorg Med Chem 2016; 24:6370-6378. [PMID: 27769673 PMCID: PMC5279723 DOI: 10.1016/j.bmc.2016.09.048] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Revised: 09/17/2016] [Accepted: 09/19/2016] [Indexed: 01/23/2023]
Abstract
The looming antibiotic crisis has prompted the development of new strategies towards fighting infection. Traditional antibiotics target bacterial processes essential for viability, whereas proposed antivirulence approaches rely on the inhibition of factors that are required only for the initiation and propagation of infection within a host. Although antivirulence compounds have yet to prove their efficacy in the clinic, bacterial signal peptidase I (SPase) represents an attractive target in that SPase inhibitors exhibit broad-spectrum antibiotic activity, but even at sub-MIC doses also impair the secretion of essential virulence factors. The potential consequences of SPase inhibition on bacterial virulence have not been thoroughly examined, and are explored within this review. In addition, we review growing evidence that SPase has relevant biological functions outside of mediating secretion, and discuss how the inhibition of these functions may be clinically significant.
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Affiliation(s)
- Shawn I Walsh
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Arryn Craney
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Floyd E Romesberg
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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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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Robins-Browne RM, Holt KE, Ingle DJ, Hocking DM, Yang J, Tauschek M. Are Escherichia coli Pathotypes Still Relevant in the Era of Whole-Genome Sequencing? Front Cell Infect Microbiol 2016; 6:141. [PMID: 27917373 PMCID: PMC5114240 DOI: 10.3389/fcimb.2016.00141] [Citation(s) in RCA: 82] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Accepted: 10/13/2016] [Indexed: 12/15/2022] Open
Abstract
The empirical and pragmatic nature of diagnostic microbiology has given rise to several different schemes to subtype E.coli, including biotyping, serotyping, and pathotyping. These schemes have proved invaluable in identifying and tracking outbreaks, and for prognostication in individual cases of infection, but they are imprecise and potentially misleading due to the malleability and continuous evolution of E. coli. Whole genome sequencing can be used to accurately determine E. coli subtypes that are based on allelic variation or differences in gene content, such as serotyping and pathotyping. Whole genome sequencing also provides information about single nucleotide polymorphisms in the core genome of E. coli, which form the basis of sequence typing, and is more reliable than other systems for tracking the evolution and spread of individual strains. A typing scheme for E. coli based on genome sequences that includes elements of both the core and accessory genomes, should reduce typing anomalies and promote understanding of how different varieties of E. coli spread and cause disease. Such a scheme could also define pathotypes more precisely than current methods.
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Affiliation(s)
- Roy M Robins-Browne
- Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, The University of MelbourneParkville, VIC, Australia; Murdoch Childrens Research Institute, Royal Children's HospitalParkville, VIC, Australia
| | - Kathryn E Holt
- Centre for Systems Genomics, The University of MelbourneParkville, VIC, Australia; Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, The University of MelbourneParkville, VIC, Australia
| | - Danielle J Ingle
- Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, The University of MelbourneParkville, VIC, Australia; Centre for Systems Genomics, The University of MelbourneParkville, VIC, Australia; Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, The University of MelbourneParkville, VIC, Australia
| | - Dianna M Hocking
- Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, The University of Melbourne Parkville, VIC, Australia
| | - Ji Yang
- Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, The University of Melbourne Parkville, VIC, Australia
| | - Marija Tauschek
- Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, The University of Melbourne Parkville, VIC, Australia
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Rapid and Specific Polymerase Chain Reaction-Enzyme Linked Immunosorbent Assay for Detection of Escherichia coli LT Toxin From Clinical Isolates. ARCHIVES OF CLINICAL INFECTIOUS DISEASES 2016. [DOI: 10.5812/archcid.36261] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Secreted Compounds of the Probiotic Bacillus clausii Strain O/C Inhibit the Cytotoxic Effects Induced by Clostridium difficile and Bacillus cereus Toxins. Antimicrob Agents Chemother 2016; 60:3445-54. [PMID: 27001810 DOI: 10.1128/aac.02815-15] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Accepted: 03/15/2016] [Indexed: 12/18/2022] Open
Abstract
Although the use of probiotics based on Bacillus strains to fight off intestinal pathogens and antibiotic-associated diarrhea is widespread, the mechanisms involved in producing their beneficial effects remain unclear. Here, we studied the ability of compounds secreted by the probiotic Bacillus clausii strain O/C to counteract the cytotoxic effects induced by toxins of two pathogens, Clostridium difficile and Bacillus cereus, by evaluating eukaryotic cell viability and expression of selected genes. Coincubation of C. difficile and B. cereus toxic culture supernatants with the B. clausii supernatant completely prevented the damage induced by toxins in Vero and Caco-2 cells. The hemolytic effect of B. cereus was also avoided by the probiotic supernatant. Moreover, in these cells, the expression of rhoB, encoding a Rho GTPase target for C. difficile toxins, was normalized when C. difficile supernatant was pretreated using the B. clausii supernatant. All of the beneficial effects observed with the probiotic were abolished by the serine protease inhibitor phenylmethylsulfonyl fluoride (PMSF). Suspecting the involvement of a secreted protease in this protective effect, a protease was purified from the B. clausii supernatant and identified as a serine protease (M-protease; GenBank accession number Q99405). Experiments on Vero cells demonstrated the antitoxic activity of the purified protease against pathogen supernatants. This is the first report showing the capacity of a protease secreted by probiotic bacteria to inhibit the cytotoxic effects of toxinogenic C. difficile and B. cereus strains. This extracellular compound could be responsible, at least in part, for the protective effects observed for this human probiotic in antibiotic-associated diarrhea.
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Binding of CFA/I Pili of Enterotoxigenic Escherichia coli to Asialo-GM1 Is Mediated by the Minor Pilin CfaE. Infect Immun 2016; 84:1642-1649. [PMID: 26975993 DOI: 10.1128/iai.01562-15] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Accepted: 03/06/2016] [Indexed: 11/20/2022] Open
Abstract
CFA/I pili are representatives of a large family of related pili that mediate the adherence of enterotoxigenic Escherichia coli to intestinal epithelial cells. They are assembled via the alternate chaperone-usher pathway and consist of two subunits, CfaB, which makes up the pilus shaft and a single pilus tip-associated subunit, CfaE. The current model of pilus-mediated adherence proposes that CFA/I has two distinct binding activities; the CfaE subunit is responsible for binding to receptors of unknown structure on erythrocyte and intestinal epithelial cell surfaces, while CfaB binds to various glycosphingolipids, including asialo-GM1. In this report, we present two independent lines of evidence that, contrary to the existing model, CfaB does not bind to asialo-GM1 independently of CfaE. Neither purified CfaB subunits nor CfaB assembled into pili bind to asialo-GM1. Instead, we demonstrate that binding activity toward asialo-GM1 resides in CfaE and this is essential for pilus binding to Caco-2 intestinal epithelial cells. We conclude that the binding activities of CFA/I pili for asialo-GM1, erythrocytes, and intestinal cells are inseparable, require the same amino acid residues in CfaE, and therefore depend on the same or very similar binding mechanisms.
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Curtis B, Grassel C, Laufer RS, Sears KT, Pasetti MF, Barry EM, Simon R. Simple method for purification of enterotoxigenic Escherichia coli fimbriae. Protein Expr Purif 2015; 119:130-5. [PMID: 26581778 DOI: 10.1016/j.pep.2015.11.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Revised: 10/20/2015] [Accepted: 11/08/2015] [Indexed: 11/15/2022]
Abstract
Enterotoxigenic Escherichia coli (ETEC) are endemic pathogens in the developing world. They frequently cause illness in travelers, and are among the most prevalent causes of diarrheal disease in children. Pathogenic ETEC strains employ fimbriae as adhesion factors to bind the luminal surface of the intestinal epithelium and establish infection. Accordingly, there is marked interest in immunoprophylactic strategies targeting fimbriae to protect against ETEC infections. Multiple strategies have been reported for purification of ETEC fimbriae, however none is ideal. Purification has typically involved the use of highly virulent wild-type strains. We report here a simple and improved method to purify ETEC fimbriae, which was applied to obtain two different Class 5 fimbriae types of clinical relevance (CFA/I and CS4) expressed recombinantly in E. coli production strains. Following removal from cells by shearing, fimbriae proteins were purified by orthogonal purification steps employing ultracentrifugation, precipitation, and ion-exchange membrane chromatography. Purified fimbriae demonstrated the anticipated size and morphology by electron microscopy analysis, contained negligible levels of residual host cell proteins, nucleic acid, and endotoxin, and were recognized by convalescent human anti-sera.
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Affiliation(s)
- Brittany Curtis
- Center for Vaccine Development, University of Maryland Medical School, Baltimore, MD, USA; Department of Medicine, University of Maryland Medical School, Baltimore, MD, USA
| | - Christen Grassel
- Center for Vaccine Development, University of Maryland Medical School, Baltimore, MD, USA; Department of Medicine, University of Maryland Medical School, Baltimore, MD, USA
| | - Rachel S Laufer
- Center for Vaccine Development, University of Maryland Medical School, Baltimore, MD, USA; Department of Medicine, University of Maryland Medical School, Baltimore, MD, USA
| | - Khandra T Sears
- Center for Vaccine Development, University of Maryland Medical School, Baltimore, MD, USA; Department of Pediatrics, University of Maryland Medical School, Baltimore, MD, USA
| | - Marcela F Pasetti
- Center for Vaccine Development, University of Maryland Medical School, Baltimore, MD, USA; Department of Pediatrics, University of Maryland Medical School, Baltimore, MD, USA
| | - Eileen M Barry
- Center for Vaccine Development, University of Maryland Medical School, Baltimore, MD, USA; Department of Medicine, University of Maryland Medical School, Baltimore, MD, USA
| | - Raphael Simon
- Center for Vaccine Development, University of Maryland Medical School, Baltimore, MD, USA; Department of Medicine, University of Maryland Medical School, Baltimore, MD, USA.
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