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Manisha Y, Srinivasan M, Jobichen C, Rosenshine I, Sivaraman J. Sensing for survival: specialised regulatory mechanisms of Type III secretion systems in Gram-negative pathogens. Biol Rev Camb Philos Soc 2024; 99:837-863. [PMID: 38217090 DOI: 10.1111/brv.13047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Revised: 12/14/2023] [Accepted: 12/19/2023] [Indexed: 01/15/2024]
Abstract
For centuries, Gram-negative pathogens have infected the human population and been responsible for numerous diseases in animals and plants. Despite advancements in therapeutics, Gram-negative pathogens continue to evolve, with some having developed multi-drug resistant phenotypes. For the successful control of infections caused by these bacteria, we need to widen our understanding of the mechanisms of host-pathogen interactions. Gram-negative pathogens utilise an array of effector proteins to hijack the host system to survive within the host environment. These proteins are secreted into the host system via various secretion systems, including the integral Type III secretion system (T3SS). The T3SS spans two bacterial membranes and one host membrane to deliver effector proteins (virulence factors) into the host cell. This multifaceted process has multiple layers of regulation and various checkpoints. In this review, we highlight the multiple strategies adopted by these pathogens to regulate or maintain virulence via the T3SS, encompassing the regulation of small molecules to sense and communicate with the host system, as well as master regulators, gatekeepers, chaperones, and other effectors that recognise successful host contact. Further, we discuss the regulatory links between the T3SS and other systems, like flagella and metabolic pathways including the tricarboxylic acid (TCA) cycle, anaerobic metabolism, and stringent cell response.
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Affiliation(s)
- Yadav Manisha
- Department of Biological Sciences, National University of Singapore, Singapore, 117543, Singapore
| | - Mahalashmi Srinivasan
- Department of Biological Sciences, National University of Singapore, Singapore, 117543, Singapore
| | - Chacko Jobichen
- Department of Biological Sciences, National University of Singapore, Singapore, 117543, Singapore
| | - Ilan Rosenshine
- Department of Microbiology and Molecular Genetics, The Hebrew University of Jerusalem, Ein Kerem, Jerusalem, 91120, Israel
| | - J Sivaraman
- Department of Biological Sciences, National University of Singapore, Singapore, 117543, Singapore
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Muche S, El-Fenej J, Mihaita A, Mrozek Z, Cleary S, Critelli B, Marino M, Yu W, Amos B, Hunter T, Riga M, Buerkert T, Bhatt S. The two sRNAs OmrA and OmrB indirectly repress transcription from the LEE1 promoter of enteropathogenic Escherichia coli. Folia Microbiol (Praha) 2023; 68:415-430. [PMID: 36547806 DOI: 10.1007/s12223-022-01025-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Accepted: 11/26/2022] [Indexed: 12/24/2022]
Abstract
Enteropathogenic Escherichia coli (EPEC) is a diarrheagenic bacterium that predominantly infects infants in developing countries. EPEC forms attaching and effacing (A/E) lesions on the apical surface of the small intestine, leading to diarrhea. The locus of enterocyte effacement (LEE) is both necessary and sufficient for A/E lesion morphogenesis by EPEC. Gene expression from this virulence determinant is controlled by an elaborate regulatory web that extends beyond protein-based transcriptional regulators and includes small regulatory RNA (sRNA) that exert their effects posttranscriptionally. To date, only 4 Hfq-dependent sRNAs-MgrR, RyhB, McaS, and Spot42-have been identified that affect the LEE of EPEC by diverse mechanisms and elicit varying regulatory outcomes. In this study, we demonstrate that the paralogous Hfq-dependent sRNAs OmrA and OmrB globally silence the LEE to diminish the ability of EPEC to form A/E lesions. Interestingly, OmrA and OmrB do not appear to directly target a LEE-encoded gene; rather, they repress transcription from the LEE1 promoter indirectly, by means of an as-yet-unidentified transcriptional factor that binds within 200 base pairs upstream of the transcription start site to reduce the expression of the LEE master regulator Ler, which, in turn, leads to reduced morphogenesis of A/E lesions. Additionally, OmrA and OmrB also repress motility in EPEC by targeting the 5' UTR of the flagellar master regulator, flhD.
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Affiliation(s)
- Sarah Muche
- Department of Biology, Saint Joseph's University, 5600 City Avenue, SC124, Philadelphia, PA, 19131, USA
| | - Jihad El-Fenej
- Department of Biology, Saint Joseph's University, 5600 City Avenue, SC124, Philadelphia, PA, 19131, USA
- Center for Immunity and Inflammation and Department of Pathology, New Jersey Medical School, Rutgers-The State University of New Jersey, Newark, NJ, USA
| | - Alexa Mihaita
- Department of Biology, Saint Joseph's University, 5600 City Avenue, SC124, Philadelphia, PA, 19131, USA
| | - Zoe Mrozek
- Department of Biology, Saint Joseph's University, 5600 City Avenue, SC124, Philadelphia, PA, 19131, USA
| | - Sean Cleary
- Department of Biology, Saint Joseph's University, 5600 City Avenue, SC124, Philadelphia, PA, 19131, USA
- Philadelphia College of Osteopathic Medicine, 4170 City Avenue, Philadelphia, PA, 19131, USA
| | - Brian Critelli
- Department of Biology, Saint Joseph's University, 5600 City Avenue, SC124, Philadelphia, PA, 19131, USA
| | - Mary Marino
- Department of Biology, Saint Joseph's University, 5600 City Avenue, SC124, Philadelphia, PA, 19131, USA
| | - Wenlan Yu
- Department of Biology, Saint Joseph's University, 5600 City Avenue, SC124, Philadelphia, PA, 19131, USA
| | - Brianna Amos
- Department of Biology, Saint Joseph's University, 5600 City Avenue, SC124, Philadelphia, PA, 19131, USA
| | - Tressa Hunter
- Department of Biology, Saint Joseph's University, 5600 City Avenue, SC124, Philadelphia, PA, 19131, USA
| | - Michael Riga
- Department of Biology, Saint Joseph's University, 5600 City Avenue, SC124, Philadelphia, PA, 19131, USA
| | - Thomas Buerkert
- Department of Biology, Saint Joseph's University, 5600 City Avenue, SC124, Philadelphia, PA, 19131, USA
| | - Shantanu Bhatt
- Department of Biology, Saint Joseph's University, 5600 City Avenue, SC124, Philadelphia, PA, 19131, USA.
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Lara-Ochoa C, Huerta-Saquero A, Medrano-López A, Deng W, Finlay BB, Martínez-Laguna Y, Puente JL. GrlR, a negative regulator in enteropathogenic E. coli, also represses the expression of LEE virulence genes independently of its interaction with its cognate partner GrlA. Front Microbiol 2023; 14:1063368. [PMID: 36876072 PMCID: PMC9979310 DOI: 10.3389/fmicb.2023.1063368] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Accepted: 01/23/2023] [Indexed: 02/18/2023] Open
Abstract
Introduction Enteropathogenic Escherichia coli (EPEC), enterohemorrhagic E. coli (EHEC) and Citrobacter rodentium (CR) belong to a group of pathogens that share the ability to form "attaching and effacing" (A/E) lesions on the intestinal epithelia. A pathogenicity island known as the locus of enterocyte effacement (LEE) contains the genes required for A/E lesion formation. The specific regulation of LEE genes relies on three LEE-encoded regulators: Ler activates the expression of the LEE operons by antagonizing the silencing effect mediated by the global regulator H-NS, GrlA activates ler expression and GrlR represses the expression of the LEE by interacting with GrlA. However, despite the existing knowledge of LEE regulation, the interplay between GrlR and GrlA and their independent roles in gene regulation in A/E pathogens are still not fully understood. Methods To further explore the role that GrlR and GrlA in the regulation of the LEE, we used different EPEC regulatory mutants and cat transcriptional fusions, and performed protein secretion and expression assays, western blotting and native polyacrylamide gel electrophoresis. Results and discussion We showed that the transcriptional activity of LEE operons increased under LEE-repressing growth conditions in the absence of GrlR. Interestingly, GrlR overexpression exerted a strong repression effect over LEE genes in wild-type EPEC and, unexpectedly, even in the absence of H-NS, suggesting that GrlR plays an alternative repressor role. Moreover, GrlR repressed the expression of LEE promoters in a non-EPEC background. Experiments with single and double mutants showed that GrlR and H-NS negatively regulate the expression of LEE operons at two cooperative yet independent levels. In addition to the notion that GrlR acts as a repressor by inactivating GrlA through protein-protein interactions, here we showed that a DNA-binding defective GrlA mutant that still interacts with GrlR prevented GrlR-mediated repression, suggesting that GrlA has a dual role as a positive regulator by antagonizing GrlR's alternative repressor role. In line with the importance of the GrlR-GrlA complex in modulating LEE gene expression, we showed that GrlR and GrlA are expressed and interact under both inducing and repressing conditions. Further studies will be required to determine whether the GrlR alternative repressor function depends on its interaction with DNA, RNA, or another protein. These findings provide insight into an alternative regulatory pathway that GrlR employs to function as a negative regulator of LEE genes.
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Affiliation(s)
- Cristina Lara-Ochoa
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Mexico.,Centro de Detección Biomolecular, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico
| | - Alejandro Huerta-Saquero
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Mexico.,Departamento de Bionanotecnología, Centro de Nanociencias y Nanotecnología, Universidad Nacional Autónoma de México, Ensenada, Mexico
| | - Abraham Medrano-López
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Mexico
| | - Wanyin Deng
- Michael Smith Laboratories, Department of Microbiology and Immunology, and Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada
| | - B Brett Finlay
- Michael Smith Laboratories, Department of Microbiology and Immunology, and Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada
| | - Ygnacio Martínez-Laguna
- Vicerrectoría de Investigación y Estudios de Posgrado, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico
| | - José L Puente
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Mexico
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Gelalcha BD, Brown SM, Crocker HE, Agga GE, Kerro Dego O. Regulation Mechanisms of Virulence Genes in Enterohemorrhagic Escherichia coli. Foodborne Pathog Dis 2022; 19:598-612. [PMID: 35921067 DOI: 10.1089/fpd.2021.0103] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Enterohemorrhagic Escherichia coli (EHEC) is one of the most common E. coli pathotypes reported to cause several outbreaks of foodborne illnesses. EHEC is a zoonotic pathogen, and ruminants, especially cattle, are considered important reservoirs for the most common EHEC serotype, E. coli O157:H7. Humans are infected indirectly through the consumption of food (milk, meat, leafy vegetables, and fruits) and water contaminated by animal feces or direct contact with carrier animals or humans. E. coli O157:H7 is one of the most frequently reported causes of foodborne illnesses in developed countries. It employs two essential virulence mechanisms to trigger damage to the host. These are the development of attaching and effacing (AE) phenotypes on the intestinal mucosa of the host and the production of Shiga toxin (Stx) that causes hemorrhagic colitis and hemolytic uremic syndrome. The AE phenotype is controlled by the pathogenicity island, the locus of enterocyte effacement (LEE). The induction of both AE and Stx is under strict and highly complex regulatory mechanisms. Thus, a good understanding of these mechanisms, major proteins expressed, and environmental cues involved in the regulation of the expression of the virulence genes is vital to finding a method to control the colonization of reservoir hosts, especially cattle, and disease development in humans. This review is a concise account of the current state of knowledge of virulence gene regulation in the LEE-positive EHEC.
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Affiliation(s)
- Benti D Gelalcha
- Department of Animal Science, The University of Tennessee Institute of Agriculture, Knoxville, Tennessee, USA
| | - Selina M Brown
- Department of Animal Science, The University of Tennessee Institute of Agriculture, Knoxville, Tennessee, USA
| | - Hannah E Crocker
- Department of Animal Science, The University of Tennessee Institute of Agriculture, Knoxville, Tennessee, USA
| | - Getahun E Agga
- Food Animal Environmental Systems Research Unit, Agricultural Research Service, United States Department of Agriculture, Bowling Green, Kentucky, USA
| | - Oudessa Kerro Dego
- Department of Animal Science, The University of Tennessee Institute of Agriculture, Knoxville, Tennessee, USA
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Ledwaba SE, Costa DVS, Bolick DT, Giallourou N, Medeiros PHQS, Swann JR, Traore AN, Potgieter N, Nataro JP, Guerrant RL. Enteropathogenic Escherichia coli Infection Induces Diarrhea, Intestinal Damage, Metabolic Alterations, and Increased Intestinal Permeability in a Murine Model. Front Cell Infect Microbiol 2020; 10:595266. [PMID: 33392105 PMCID: PMC7773950 DOI: 10.3389/fcimb.2020.595266] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2020] [Accepted: 11/11/2020] [Indexed: 12/15/2022] Open
Abstract
Enteropathogenic E. coli (EPEC) are recognized as one of the leading bacterial causes of infantile diarrhea worldwide. Weaned C57BL/6 mice pretreated with antibiotics were challenged orally with wild-type EPEC or escN mutant (lacking type 3 secretion system) to determine colonization, inflammatory responses and clinical outcomes during infection. Antibiotic disruption of intestinal microbiota enabled efficient colonization by wild-type EPEC resulting in growth impairment and diarrhea. Increase in inflammatory biomarkers, chemokines, cellular recruitment and pro-inflammatory cytokines were observed in intestinal tissues. Metabolomic changes were also observed in EPEC infected mice with changes in tricarboxylic acid (TCA) cycle intermediates, increased creatine excretion and shifts in gut microbial metabolite levels. In addition, by 7 days after infection, although weights were recovering, EPEC-infected mice had increased intestinal permeability and decreased colonic claudin-1 levels. The escN mutant colonized the mice with no weight loss or increased inflammatory biomarkers, showing the importance of the T3SS in EPEC virulence in this model. In conclusion, a murine infection model treated with antibiotics has been developed to mimic clinical outcomes seen in children with EPEC infection and to examine potential roles of selected virulence traits. This model can help in further understanding mechanisms involved in the pathogenesis of EPEC infections and potential outcomes and thus assist in the development of potential preventive or therapeutic interventions.
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Affiliation(s)
- Solanka E. Ledwaba
- Department of Microbiology, University of Venda, Thohoyandou, South Africa
| | - Deiziane V. S. Costa
- Department of Physiology and Pharmacology, Federal University of Ceará, Fortaleza, Brazil
| | - David T. Bolick
- Center for Global Health, Division of Infectious Disease and International Health, University of Virginia School of Medicine, Charlottesville, VA, United States
| | - Natasa Giallourou
- Faculty of Medicine, Department of Metabolism, Digestion and Reproduction, Imperial College, London, England
| | | | - Jonathan R. Swann
- Faculty of Medicine, Department of Metabolism, Digestion and Reproduction, Imperial College, London, England
| | - Afsatou N. Traore
- Department of Microbiology, University of Venda, Thohoyandou, South Africa
| | - Natasha Potgieter
- Department of Microbiology, University of Venda, Thohoyandou, South Africa
| | - James P. Nataro
- Department of Pediatrics, University of Virginia School of Medicine, Charlottesville, VA, United States
| | - Richard L. Guerrant
- Center for Global Health, Division of Infectious Disease and International Health, University of Virginia School of Medicine, Charlottesville, VA, United States
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Saran R, Wang Y, Li ITS. Mechanical Flexibility of DNA: A Quintessential Tool for DNA Nanotechnology. SENSORS (BASEL, SWITZERLAND) 2020; 20:E7019. [PMID: 33302459 PMCID: PMC7764255 DOI: 10.3390/s20247019] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Revised: 12/04/2020] [Accepted: 12/04/2020] [Indexed: 02/06/2023]
Abstract
The mechanical properties of DNA have enabled it to be a structural and sensory element in many nanotechnology applications. While specific base-pairing interactions and secondary structure formation have been the most widely utilized mechanism in designing DNA nanodevices and biosensors, the intrinsic mechanical rigidity and flexibility are often overlooked. In this article, we will discuss the biochemical and biophysical origin of double-stranded DNA rigidity and how environmental and intrinsic factors such as salt, temperature, sequence, and small molecules influence it. We will then take a critical look at three areas of applications of DNA bending rigidity. First, we will discuss how DNA's bending rigidity has been utilized to create molecular springs that regulate the activities of biomolecules and cellular processes. Second, we will discuss how the nanomechanical response induced by DNA rigidity has been used to create conformational changes as sensors for molecular force, pH, metal ions, small molecules, and protein interactions. Lastly, we will discuss how DNA's rigidity enabled its application in creating DNA-based nanostructures from DNA origami to nanomachines.
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Affiliation(s)
- Runjhun Saran
- Department of Chemistry, Biochemistry and Molecular Biology, Irving K. Barber Faculty of Science, The University of British Columbia, Kelowna, BC V1V1V7, Canada;
| | - Yong Wang
- Department of Physics, Materials Science and Engineering Program, Cell and Molecular Biology Program, University of Arkansas, Fayetteville, AR 72701, USA;
| | - Isaac T. S. Li
- Department of Chemistry, Biochemistry and Molecular Biology, Irving K. Barber Faculty of Science, The University of British Columbia, Kelowna, BC V1V1V7, Canada;
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Serapio-Palacios A, Finlay BB. Dynamics of expression, secretion and translocation of type III effectors during enteropathogenic Escherichia coli infection. Curr Opin Microbiol 2020; 54:67-76. [PMID: 32058947 DOI: 10.1016/j.mib.2019.12.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Accepted: 12/30/2019] [Indexed: 12/14/2022]
Abstract
Enteropathogenic Escherichia coli (EPEC) is an important cause of infant diarrhea and mortality worldwide. The locus of enterocyte effacement (LEE) pathogenicity island in the EPEC genome encodes a type 3 secretion system (T3SS). This nanomachine directly injects a sophisticated arsenal of effectors into host cells, which is critical for EPEC pathogenesis. To colonize the gut mucosa, EPEC alters its gene expression in response to host environmental signals. Regulation of the LEE has been studied extensively, revealing key mechanisms of transcriptional regulation, and more recently at the posttranscriptional and posttranslational levels. Moreover, the T3SS assembly and secretion is a highly coordinated process that ensures hierarchical delivery of effectors upon cell contact. EPEC effectors and virulence factors not only manipulate host cellular processes, but also modulate effector translocation by controlling T3SS formation. In this review, we focus on the regulation of EPEC virulence genes and modulation of effector secretion and translocation.
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Affiliation(s)
| | - Barton Brett Finlay
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada; Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada; Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada.
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8
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Pokharel P, Habouria H, Bessaiah H, Dozois CM. Serine Protease Autotransporters of the Enterobacteriaceae (SPATEs): Out and About and Chopping It Up. Microorganisms 2019; 7:E594. [PMID: 31766493 PMCID: PMC6956023 DOI: 10.3390/microorganisms7120594] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Accepted: 11/13/2019] [Indexed: 02/06/2023] Open
Abstract
Autotransporters are secreted proteins with multiple functions produced by a variety of Gram-negative bacteria. In Enterobacteriaceae, a subgroup of these autotransporters are the SPATEs (serine protease autotransporters of Enterobacteriaceae). SPATEs play a crucial role in survival and virulence of pathogens such as Escherichia coli and Shigella spp. and contribute to intestinal and extra-intestinal infections. These high molecular weight proteases are transported to the external milieu by the type Va secretion system and function as proteases with diverse substrate specificities and biological functions including adherence and cytotoxicity. Herein, we provide an overview of SPATEs and discuss recent findings on the biological roles of these secreted proteins, including proteolysis of substrates, adherence to cells, modulation of the immune response, and virulence in host models. In closing, we highlight recent insights into the regulation of expression of SPATEs that could be exploited to understand fundamental SPATE biology.
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Affiliation(s)
- Pravil Pokharel
- Institut National de Recherche Scientifique (INRS)-Centre Armand-Frappier Santé Biotechnologie, Laval, QC H7V 1B7, Canada; (P.P.); (H.H.); (H.B.)
- Centre de Recherche en Infectiologie Porcine et Avicole (CRIPA), Saint-Hyacinthe, QC J2S 2M2, Canada
| | - Hajer Habouria
- Institut National de Recherche Scientifique (INRS)-Centre Armand-Frappier Santé Biotechnologie, Laval, QC H7V 1B7, Canada; (P.P.); (H.H.); (H.B.)
- Centre de Recherche en Infectiologie Porcine et Avicole (CRIPA), Saint-Hyacinthe, QC J2S 2M2, Canada
| | - Hicham Bessaiah
- Institut National de Recherche Scientifique (INRS)-Centre Armand-Frappier Santé Biotechnologie, Laval, QC H7V 1B7, Canada; (P.P.); (H.H.); (H.B.)
- Centre de Recherche en Infectiologie Porcine et Avicole (CRIPA), Saint-Hyacinthe, QC J2S 2M2, Canada
| | - Charles M. Dozois
- Institut National de Recherche Scientifique (INRS)-Centre Armand-Frappier Santé Biotechnologie, Laval, QC H7V 1B7, Canada; (P.P.); (H.H.); (H.B.)
- Centre de Recherche en Infectiologie Porcine et Avicole (CRIPA), Saint-Hyacinthe, QC J2S 2M2, Canada
- Institut Pasteur International Network, Laval, QC H7V 1B7, Canada
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9
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Platenkamp A, Mellies JL. Environment Controls LEE Regulation in Enteropathogenic Escherichia coli. Front Microbiol 2018; 9:1694. [PMID: 30140259 PMCID: PMC6094958 DOI: 10.3389/fmicb.2018.01694] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Accepted: 07/09/2018] [Indexed: 12/11/2022] Open
Abstract
Enteropathogenic Escherichia coli (EPEC) is a significant cause of infant morbidity and mortality in developing regions of the world. Horizontally acquired genetic elements encode virulence structures, effectors, and regulators that promote bacterial colonization and disease. One such genetic element, the locus of enterocyte effacement (LEE), encodes the type three secretion system (T3SS) which acts as a bridge between bacterial and host cells to pass effector molecules that exert changes on the host. Due to its importance in EPEC virulence, regulation of the LEE has been of high priority and its investigation has elucidated many virulence regulators, including master regulator of the LEE Ler, H-NS, other nucleoid-associated proteins, GrlA, and PerC. Media type, environmental signals, sRNA signaling, metabolic processes, and stress responses have profound, strain-specific effects on regulators and LEE expression, and thus T3SS formation. Here we review virulence gene regulation in EPEC, which includes approaches for lessening disease by exploiting the elucidated regulatory pathways.
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Affiliation(s)
- Amy Platenkamp
- Department of Biology, Reed College, Portland, OR, United States
| | - Jay L Mellies
- Department of Biology, Reed College, Portland, OR, United States
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10
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Regulation of the Locus of Enterocyte Effacement in Attaching and Effacing Pathogens. J Bacteriol 2017; 200:JB.00336-17. [PMID: 28760850 DOI: 10.1128/jb.00336-17] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Attaching and effacing (AE) pathogens colonize the gut mucosa using a type three secretion system (T3SS) and a suite of effector proteins. The locus of enterocyte effacement (LEE) is the defining genetic feature of the AE pathogens, encoding the T3SS and the core effector proteins necessary for pathogenesis. Extensive research has revealed a complex regulatory network that senses and responds to a myriad of host- and microbiota-derived signals in the infected gut to control transcription of the LEE. These signals include microbiota-liberated sugars and metabolites in the gut lumen, molecular oxygen at the gut epithelium, and host hormones. Recent research has revealed that AE pathogens also recognize physical signals, such as attachment to the epithelium, and that the act of effector translocation remodels gene expression in infecting bacteria. In this review, we summarize our knowledge to date and present an integrated view of how chemical, geographical, and physical cues regulate the virulence program of AE pathogens during infection.
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11
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Ogawa R, Yen H, Kawasaki K, Tobe T. Activation of lpxR gene through enterohaemorrhagic Escherichia coli virulence regulators mediates lipid A modification to attenuate innate immune response. Cell Microbiol 2017; 20. [PMID: 29112299 DOI: 10.1111/cmi.12806] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Revised: 11/01/2017] [Accepted: 11/01/2017] [Indexed: 01/02/2023]
Abstract
During the course of infection, pathogens must overcome a variety of host defence systems. Modulation of lipid A, which is a strong stimulant for host immune systems, is one of the strategies used by microorganisms to evade the host response. The lpxR gene, which encodes a lipid A 3'-O-deacylase, is commonly found in several pathogens and has been shown to reduce the inflammatory response. Here, we demonstrated that the lpxR gene of enterohaemorrhagic Escherichia coli (EHEC) was positively regulated by two virulence regulators, Pch and Ler, and that this regulation was coordinated with the locus of enterocyte effacement genes, which encode major virulence factors for colonisation. The lpxR promoter was repressed by the binding of H-NS, but the competitive binding of both regulators resulted in transcription activation. Next, we showed that lipid A from the lpxR mutant was more stimulatory of the inflammatory response in macrophage-like cells than lipid A from wild-type EHEC. Furthermore, phagocytic activity and phagosome maturation in host cells infected with the lpxR mutant were increased in a p38 mitogen-activated protein kinase-dependent manner in comparison with wild-type EHEC infection. Finally, we demonstrated that the pch mutant, which is deficient in activation of the locus of enterocyte effacement genes, was phagocytised more efficiently than the wild type. Thus, EHEC modulates lipid A to dampen the host immune response when activating virulence genes for colonisation.
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Affiliation(s)
- Rikako Ogawa
- Department of Biomedical Informatics, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Hilo Yen
- Department of Biomedical Informatics, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Kiyoshi Kawasaki
- Faculty of Pharmaceutical Science, Doshisha Women's College, Kyoto, Japan
| | - Toru Tobe
- Department of Biomedical Informatics, Osaka University Graduate School of Medicine, Osaka, Japan
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12
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Katsowich N, Elbaz N, Pal RR, Mills E, Kobi S, Kahan T, Rosenshine I. Host cell attachment elicits posttranscriptional regulation in infecting enteropathogenic bacteria. Science 2017; 355:735-739. [DOI: 10.1126/science.aah4886] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Accepted: 01/19/2017] [Indexed: 01/04/2023]
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13
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Ronin I, Katsowich N, Rosenshine I, Balaban NQ. A long-term epigenetic memory switch controls bacterial virulence bimodality. eLife 2017; 6. [PMID: 28178445 PMCID: PMC5295817 DOI: 10.7554/elife.19599] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Accepted: 01/17/2017] [Indexed: 12/22/2022] Open
Abstract
When pathogens enter the host, sensing of environmental cues activates the expression of virulence genes. Opposite transition of pathogens from activating to non-activating conditions is poorly understood. Interestingly, variability in the expression of virulence genes upon infection enhances colonization. In order to systematically detect the role of phenotypic variability in enteropathogenic E. coli (EPEC), an important human pathogen, both in virulence activating and non-activating conditions, we employed the ScanLag methodology. The analysis revealed a bimodal growth rate. Mathematical modeling combined with experimental analysis showed that this bimodality is mediated by a hysteretic memory-switch that results in the stable co-existence of non-virulent and hyper-virulent subpopulations, even after many generations of growth in non-activating conditions. We identified the per operon as the key component of the hysteretic switch. This unique hysteretic memory switch may result in persistent infection and enhanced host-to-host spreading. DOI:http://dx.doi.org/10.7554/eLife.19599.001 Bacteria typically cope with harsh and changing environments by activating specific genes or accumulating those mutations that change genes in a beneficial way. Recently, it was also shown that the levels of gene activity can vary between otherwise identical bacteria in a single population. This provides an alternative strategy to deal with stressful conditions because it generates sub-groups of bacteria that potentially already adapted to different environments. Bacteria that enter the human body face many challenges, and this kind of pre-adaptation could help them to invade humans and overcome the immune system. However, this hypothesis had not previously been tested in a bacterium called enteropathogenic E.coli, which infects the intestines and is responsible for the deaths of many infants worldwide. Ronin et al. show that cells in enteropathogenic E.coli colonies spontaneously form into two groups when exposed to conditions that mimic the environment inside the human body. Once triggered, one of these groups is particularly dangerous and this “hypervirulent” state is remembered for an extremely long time meaning that the bacteria remain hypervirulent for many generations. In addition, Ronin et al. identified the specific genes that control the switch to the hypervirulent state. These findings have uncovered the existence of groups of enteropathogenic E.coli that are pre-adapted to invading human hosts. Finding out more about how the switching mechanism works and its relevance in other bacteria may help researchers to develop new therapies that can help fight bacterial infections. DOI:http://dx.doi.org/10.7554/eLife.19599.002
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Affiliation(s)
- Irine Ronin
- Racah Institute of Physics, Edmond J. Safra Campus, Faculty of Science, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Naama Katsowich
- Department of Microbiology and Molecular Genetics, IMRIC, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Ilan Rosenshine
- Department of Microbiology and Molecular Genetics, IMRIC, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Nathalie Q Balaban
- Racah Institute of Physics, Edmond J. Safra Campus, Faculty of Science, The Hebrew University of Jerusalem, Jerusalem, Israel
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14
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Bhatt S, Egan M, Ramirez J, Xander C, Jenkins V, Muche S, El-Fenej J, Palmer J, Mason E, Storm E, Buerkert T. Hfq and three Hfq-dependent small regulatory RNAs-MgrR, RyhB and McaS-coregulate the locus of enterocyte effacement in enteropathogenic Escherichia coli. Pathog Dis 2016; 75:ftw113. [PMID: 27956465 DOI: 10.1093/femspd/ftw113] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 07/28/2016] [Accepted: 12/10/2016] [Indexed: 11/15/2022] Open
Abstract
Enteropathogenic Escherichia coli (EPEC) is a significant cause of infantile diarrhea and death in developing countries. The pathogenicity island locus of enterocyte effacement (LEE) is essential for EPEC to cause diarrhea. Besides EPEC, the LEE is also present in other gastrointestinal pathogens, most notably enterohemorrhagic E. coli (EHEC). Whereas transcriptional control of the LEE has been meticulously examined, posttranscriptional regulation, including the role of Hfq-dependent small RNAs, remains undercharacterized. However, the past few years have witnessed a surge in the identification of riboregulators of the LEE in EHEC. Contrastingly, the posttranscriptional regulatory landscape of EPEC remains cryptic. Here we demonstrate that the RNA-chaperone Hfq represses the LEE of EPEC by targeting the 5' untranslated leader region of grlR in the grlRA mRNA. Three conserved small regulatory RNAs (sRNAs)-MgrR, RyhB and McaS-are involved in the Hfq-dependent regulation of grlRA MgrR and RyhB exert their effects by directly base-pairing to the 5' region of grlR Whereas MgrR selectively represses grlR but activates grlA, RyhB represses gene expression from the entire grlRA transcript. Meanwhile, McaS appears to target the grlRA mRNA indirectly. Thus, our results provide the first definitive evidence that implicates multiple sRNAs in regulating the LEE and the resulting virulence of EPEC.
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Affiliation(s)
- Shantanu Bhatt
- Department of Biology, Saint Joseph's University, 5600 City Avenue, Science Center, Philadelphia, PA 19131, USA
| | - Marisa Egan
- Department of Biology, Saint Joseph's University, 5600 City Avenue, Science Center, Philadelphia, PA 19131, USA
| | - Jasmine Ramirez
- Department of Biology, Saint Joseph's University, 5600 City Avenue, Science Center, Philadelphia, PA 19131, USA
| | - Christian Xander
- Department of Biology, Saint Joseph's University, 5600 City Avenue, Science Center, Philadelphia, PA 19131, USA
| | - Valerie Jenkins
- Department of Biology, Saint Joseph's University, 5600 City Avenue, Science Center, Philadelphia, PA 19131, USA
| | - Sarah Muche
- Department of Biology, Saint Joseph's University, 5600 City Avenue, Science Center, Philadelphia, PA 19131, USA
| | - Jihad El-Fenej
- Department of Biology, Saint Joseph's University, 5600 City Avenue, Science Center, Philadelphia, PA 19131, USA
| | - Jamie Palmer
- Department of Biology, Saint Joseph's University, 5600 City Avenue, Science Center, Philadelphia, PA 19131, USA
| | - Elisabeth Mason
- Department of Biology, Saint Joseph's University, 5600 City Avenue, Science Center, Philadelphia, PA 19131, USA
| | - Elizabeth Storm
- Department of Biology, Saint Joseph's University, 5600 City Avenue, Science Center, Philadelphia, PA 19131, USA
| | - Thomas Buerkert
- Department of Biology, Saint Joseph's University, 5600 City Avenue, Science Center, Philadelphia, PA 19131, USA
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15
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Amino acid residues in the Ler protein critical for derepression of the LEE5 promoter in enteropathogenic E. coli. J Microbiol 2016; 54:559-64. [PMID: 27480636 DOI: 10.1007/s12275-016-6027-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Revised: 05/30/2016] [Accepted: 06/16/2016] [Indexed: 10/21/2022]
Abstract
Enteropathogenic E. coli causes attaching and effacing (A/E) intestinal lesions. The genes involved in the formation of A/E lesions are encoded within a chromosomal island comprising of five major operons, LEE1-5. The global regulator H-NS represses the expression of these operons. Ler, a H-NS homologue, counteracts the H-NS-mediated repression. Using a novel genetic approach, we identified the amino acid residues in Ler that are involved in the interaction with H-NS: I20 and L23 in the C-terminal portion of α-helix 3, and I42 in the following unstructured linker region.
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16
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A Highly Conserved Bacterial D-Serine Uptake System Links Host Metabolism and Virulence. PLoS Pathog 2016; 12:e1005359. [PMID: 26727373 PMCID: PMC4699771 DOI: 10.1371/journal.ppat.1005359] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Accepted: 12/03/2015] [Indexed: 01/22/2023] Open
Abstract
The ability of any organism to sense and respond to challenges presented in the environment is critically important for promoting or restricting colonization of specific sites. Recent work has demonstrated that the host metabolite D-serine has the ability to markedly influence the outcome of infection by repressing the type III secretion system of enterohaemorrhagic Escherichia coli (EHEC) in a concentration-dependent manner. However, exactly how EHEC monitors environmental D-serine is not understood. In this work, we have identified two highly conserved members of the E. coli core genome, encoding an inner membrane transporter and a transcriptional regulator, which collectively help to "sense" levels of D-serine by regulating its uptake from the environment and in turn influencing global gene expression. Both proteins are required for full expression of the type III secretion system and diversely regulated prophage-encoded effector proteins demonstrating an important infection-relevant adaptation of the core genome. We propose that this system acts as a key safety net, sampling the environment for this metabolite, thereby promoting colonization of EHEC to favorable sites within the host.
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17
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Moreira CG, Sperandio V. The Epinephrine/Norepinephrine/Autoinducer-3 Interkingdom Signaling System in Escherichia coli O157:H7. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 874:247-61. [PMID: 26589223 DOI: 10.1007/978-3-319-20215-0_12] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Epinephrine/norepinephrine/AI-3 signaling is used as an interkingdom chemical signaling system between microbes and their hosts. This system is also exploited by pathogens to regulate virulence traits. In enterohemorrhagic E. coli (EHEC) O157:H7, it is essential for pathogenesis and flagella motility. These three signals activate expression of a pathogenicity island named locus of enterocyte effacement (LEE), Shiga toxin, and the flagella regulon. These signals are sensed by the two-component system QseBC, whereas the bacterial membrane receptor QseC autophosphorylates and phosphorylates the QseB response regulator initiating a complex phosphorelay signaling cascade that activates the expression of a second two-component system, QseEF. The QseEF two-component system is also involved in the expression of the virulence genes, and it senses epinephrine, phosphate, and sulfate. This complex signaling cascade still needs to be completely elucidated.
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Affiliation(s)
- Cristiano G Moreira
- Molecular Microbiology Department, University of Texas Southwestern Medical Center, 6000 Harry Hines Bvld, Dallas, 75390, TX, USA.
| | - Vanessa Sperandio
- Molecular Microbiology Department, University of Texas Southwestern Medical Center, 6000 Harry Hines Bvld, Dallas, 75390, TX, USA
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18
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Interkingdom Chemical Signaling in Enterohemorrhagic Escherichia coli O157:H7. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 874:201-13. [DOI: 10.1007/978-3-319-20215-0_9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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19
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Abstract
Escherichia colicauses three types of illnesses in humans: diarrhea, urinary tract infections, and meningitis in newborns. The acquisition of virulence-associated genes and the ability to properly regulate these, often horizontally transferred, loci distinguishes pathogens from the normally harmless commensal E. coli found within the human intestine. This review addresses our current understanding of virulence gene regulation in several important diarrhea-causing pathotypes, including enteropathogenic, enterohemorrhagic,enterotoxigenic, and enteroaggregativeE. coli-EPEC, EHEC, ETEC and EAEC, respectively. The intensely studied regulatory circuitry controlling virulence of uropathogenicE. coli, or UPEC, is also reviewed, as is that of MNEC, a common cause of meningitis in neonates. Specific topics covered include the regulation of initial attachment events necessary for infection, environmental cues affecting virulence gene expression, control of attaching and effacing lesionformation, and control of effector molecule expression and secretion via the type III secretion systems by EPEC and EHEC. How phage control virulence and the expression of the Stx toxins of EHEC, phase variation, quorum sensing, and posttranscriptional regulation of virulence determinants are also addressed. A number of important virulence regulators are described, including the AraC-like molecules PerA of EPEC, CfaR and Rns of ETEC, and AggR of EAEC;the Ler protein of EPEC and EHEC;RfaH of UPEC;and the H-NS molecule that acts to silence gene expression. The regulatory circuitry controlling virulence of these greatly varied E. colipathotypes is complex, but common themes offerinsight into the signals and regulators necessary forE. coli disease progression.
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20
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Connolly JPR, Finlay BB, Roe AJ. From ingestion to colonization: the influence of the host environment on regulation of the LEE encoded type III secretion system in enterohaemorrhagic Escherichia coli. Front Microbiol 2015; 6:568. [PMID: 26097473 PMCID: PMC4456613 DOI: 10.3389/fmicb.2015.00568] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Accepted: 05/24/2015] [Indexed: 12/21/2022] Open
Abstract
Enterohaemorrhagic Escherichia coli (EHEC) binds to host tissue and intimately attaches to intestinal cells using a dedicated type III secretion system (T3SS). This complex multi-protein organelle is encoded within a large pathogenicity island called the locus of enterocyte effacement (LEE), which is subject to extensive regulatory control. Over the past 15 years we have gained a wealth of knowledge concerning how the LEE is regulated transcriptionally by specific, global and phage encoded regulators. More recently, significant advances have been made in our understanding of how specific signals, including host or microbiota derived metabolic products and various nutrient sources, can affect how the LEE-encoded T3SS is regulated. In this review we discuss regulation of the LEE, focusing on how these physiologically relevant signals are sensed and how they affect the expression of this major virulence factor. The implications for understanding the disease process by specific regulatory mechanisms are also discussed.
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Affiliation(s)
- James P R Connolly
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow , Glasgow, UK
| | - B Brett Finlay
- Michael Smith Laboratories, University of British Columbia , Vancouver, BC, Canada
| | - Andrew J Roe
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow , Glasgow, UK
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Connolly JPR, Goldstone RJ, Burgess K, Cogdell RJ, Beatson SA, Vollmer W, Smith DGE, Roe AJ. The host metabolite D-serine contributes to bacterial niche specificity through gene selection. ISME JOURNAL 2015; 9:1039-51. [PMID: 25526369 PMCID: PMC4366372 DOI: 10.1038/ismej.2014.242] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Revised: 10/07/2014] [Accepted: 11/13/2014] [Indexed: 01/29/2023]
Abstract
Escherichia coli comprise a diverse array of both commensals and niche-specific pathotypes. The ability to cause disease results from both carriage of specific virulence factors and regulatory control of these via environmental stimuli. Moreover, host metabolites further refine the response of bacteria to their environment and can dramatically affect the outcome of the host-pathogen interaction. Here, we demonstrate that the host metabolite, D-serine, selectively affects gene expression in E. coli O157:H7. Transcriptomic profiling showed exposure to D-serine results in activation of the SOS response and suppresses expression of the Type 3 Secretion System (T3SS) used to attach to host cells. We also show that concurrent carriage of both the D-serine tolerance locus (dsdCXA) and the locus of enterocyte effacement pathogenicity island encoding a T3SS is extremely rare, a genotype that we attribute to an 'evolutionary incompatibility' between the two loci. This study demonstrates the importance of co-operation between both core and pathogenic genetic elements in defining niche specificity.
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Affiliation(s)
- James P R Connolly
- 1] Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, UK [2] School of Life Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Robert J Goldstone
- 1] Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, UK [2] School of Life Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Karl Burgess
- 1] Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, UK [2] School of Life Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Richard J Cogdell
- Institute of Molecular Cell and Systems Biology, University of Glasgow, Glasgow, UK
| | - Scott A Beatson
- School of Chemistry and Molecular Biosciences and Australian Infectious Diseases Research Centre, University of Queensland, St Lucia, Queensland, Australia
| | - Waldemar Vollmer
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne, UK
| | - David G E Smith
- 1] Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, UK [2] School of Life Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK [3] Moredun Research Institute, Pentlands Science Park, Bush Loan, Edinburgh, Midlothian, UK
| | - Andrew J Roe
- 1] Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, UK [2] School of Life Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
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Locus of enterocyte effacement: a pathogenicity island involved in the virulence of enteropathogenic and enterohemorragic Escherichia coli subjected to a complex network of gene regulation. BIOMED RESEARCH INTERNATIONAL 2015; 2015:534738. [PMID: 25710006 PMCID: PMC4332760 DOI: 10.1155/2015/534738] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Accepted: 11/03/2014] [Indexed: 12/18/2022]
Abstract
The locus of enterocyte effacement (LEE) is a 35.6 kb pathogenicity island inserted in the genome of some bacteria such as enteropathogenic Escherichia coli, enterohemorrhagic E.coli, Citrobacter rodentium, and Escherichia albertii. LEE comprises the genes responsible for causing attaching and effacing lesions, a characteristic lesion that involves intimate adherence of bacteria to enterocytes, a signaling cascade leading to brush border and microvilli destruction, and loss of ions, causing severe diarrhea. It is composed of 41 open reading frames and five major operons encoding a type three system apparatus, secreted proteins, an adhesin, called intimin, and its receptor called translocated intimin receptor (Tir). LEE is subjected to various levels of regulation, including transcriptional and posttranscriptional regulators located both inside and outside of the pathogenicity island. Several molecules were described being related to feedback inhibition, transcriptional activation, and transcriptional repression. These molecules are involved in a complex network of regulation, including mechanisms such as quorum sensing and temporal control of LEE genes transcription and translation. In this mini review we have detailed the complex network that regulates transcription and expression of genes involved in this kind of lesion.
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Abstract
Adhesins are a group of proteins in enterohemorrhagic Escherichia coli (EHEC) that are involved in the attachment or colonization of this pathogen to abiotic (plastic or steel) and biological surfaces, such as those found in bovine and human intestines. This review provides the most up-to-date information on these essential adhesion factors, summarizing important historical discoveries and analyzing the current and future state of this research. In doing so, the proteins intimin and Tir are discussed in depth, especially regarding their role in the development of attaching and effacing lesions and in EHEC virulence. Further, a series of fimbrial proteins (Lpf1, Lpf2, curli, ECP, F9, ELF, Sfp, HCP, and type 1 fimbriae) are also described, emphasizing their various contributions to adherence and colonization of different surfaces and their potential use as genetic markers in detection and classification of different EHEC serotypes. This review also discusses the role of several autotransporter proteins (EhaA-D, EspP, Saa and Sab, and Cah), as well as other proteins associated with adherence, such as flagella, EibG, Iha, and OmpA. While these proteins have all been studied to varying degrees, all of the adhesins summarized in this chapter have been linked to different stages of the EHEC life cycle, making them good targets for the development of more effective diagnostics and therapeutics.
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Affiliation(s)
- Brian D. McWilliams
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, 77555. USA
| | - Alfredo G. Torres
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, 77555. USA
- Department of Pathology and Sealy Center for Vaccine Development, University of Texas Medical Branch, Galveston, Texas, 77555. USA
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Abstract
ABSTRACT
Coordinated expression of enterohemorrhagic
Escherichia coli
virulence genes enables the bacterium to cause hemorrhagic colitis and the complication known as hemolytic-uremic syndrome. Horizontally acquired genes and those common to
E. coli
contribute to the disease process, and increased virulence gene expression is correlated with more severe disease in humans. Researchers have gained considerable knowledge about how the type III secretion system, secreted effectors, adhesin molecules, and the Shiga toxins are regulated by environmental signals and multiple genetic pathways. Also emergent from the data is an understanding of how enterohemorrhagic
E. coli
regulates response to acid stress, the role of flagellar motility, and how passage through the human host and bovine intestinal tract causes disease and supports carriage in the cattle reservoir, respectively. Particularly exciting areas of discovery include data suggesting how expression of the myriad effectors is coordinately regulated with their cognate type III secretion system and how virulence is correlated with bacterial metabolism and gut physiology.
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PafR, a novel transcription regulator, is important for pathogenesis in uropathogenic Escherichia coli. Infect Immun 2014; 82:4241-52. [PMID: 25069986 DOI: 10.1128/iai.00086-14] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The metV genomic island in the chromosome of uropathogenic Escherichia coli (UPEC) encodes a putative transcription factor and a sugar permease of the phosphotransferase system (PTS), which are predicted to compose a Bgl-like sensory system. The presence of these two genes, hereby termed pafR and pafP, respectively, has been previously shown to correlate with isolates causing clinical syndromes. We show here that deletion of both genes impairs the ability of the resulting mutant to infect the CBA/J mouse model of ascending urinary tract infection compared to that of the parent strain, CFT073. Expressing the two genes in trans in the two-gene knockout mutant complemented full virulence. Deletion of either gene individually generated the same phenotype as the double knockout, indicating that both pafR and pafP are important to pathogenesis. We screened numerous environmental conditions but failed to detect expression from the promoter that precedes the paf genes in vitro, suggesting that they are in vivo induced (ivi). Although PafR is shown here to be capable of functioning as a transcriptional antiterminator, its targets in the UPEC genome are not known. Using microarray analysis, we have shown that expression of PafR from a heterologous promoter in CFT073 affects expression of genes related to bacterial virulence, biofilm formation, and metabolism. Expression of PafR also inhibits biofilm formation and motility. Taken together, our results suggest that the paf genes are implicated in pathogenesis and that PafR controls virulence genes, in particular biofilm formation genes.
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Dynamics of expression and maturation of the type III secretion system of enteropathogenic Escherichia coli. J Bacteriol 2014; 196:2798-806. [PMID: 24837293 DOI: 10.1128/jb.00069-14] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Enteropathogenic Escherichia coli (EPEC) is a major cause of food poisoning, leading to significant morbidity and mortality. EPEC virulence is dependent on a type III secretion system (T3SS), a molecular syringe employed by EPEC to inject effector proteins into host cells. The injected effector proteins subvert host cellular functions to the benefit of the infecting bacteria. The T3SS and related genes reside in several operons clustered in the locus of enterocyte effacement (LEE). We carried out simultaneous analysis of the expression dynamics of all the LEE promoters and the rate of maturation of the T3SS. The results showed that expression of the LEE1 operon is activated immediately upon shifting the culture to inducing conditions, while expression of other LEE promoters is activated only ∼70 min postinduction. Parallel analysis showed that the T3SS becomes functional around 100 min postinduction. The T3SS core proteins EscS, EscT, EscU, and EscR are predicted to be involved in the first step of T3SS assembly and are therefore included among the LEE1 genes. However, interfering with the temporal regulation of EscS, EscT, EscU, and EscR expression has only a marginal effect on the rate of the T3SS assembly. This study provides a comprehensive description of the transcription dynamics of all the LEE genes and correlates it to that of T3SS biogenesis.
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Sharma VK, Casey TA. Determining the relative contribution and hierarchy of hha and qseBC in the regulation of flagellar motility of Escherichia coli O157:H7. PLoS One 2014; 9:e85866. [PMID: 24465756 PMCID: PMC3897532 DOI: 10.1371/journal.pone.0085866] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2013] [Accepted: 12/06/2013] [Indexed: 11/18/2022] Open
Abstract
In recent studies, we demonstrated that a deletion of hha caused increased secretion of locus of enterocyte encoded adherence proteins and reduced motility of enterohemorrhagic Escherichia coli (EHEC) O157:H7. In addition to the importance of hha in positive regulation of motility, a two-component quorum sensing pathway encoded by the qseBC genes has been shown to activate bacterial motility in response to mammalian stress hormones epinephrine and norepinephrine as well as bacterially produced autoinducer-3. In this study, we compared regulatory contribution and hierarchy of hha, a member of the Hha/YmoA family of nucleoid-associated proteins, to that of qseBC in the expression of EHEC O157:H7 motility. Since norepinephrine affects motility of EHEC O157:H7 through a qseBC-encoded two-component quorum sensing signaling, we also determined whether the hha-mediated regulation of motility is affected by norepinephrine and whether this effect is qseBC dependent. We used single (Δhha or ΔqseC) and double (Δhha ΔqseC) deletion mutants to show that hha exerts a greater positive regulatory effect in comparison to qseBC on the expression of motility by EHEC O157:H7. We also show that Hha is hierarchically superior in transcriptional regulation of motility than QseBC because transcription of qseC was significantly reduced in the hha deletion mutant compared to that in the parental and the hha-complemented mutant strains. These results suggest that hha regulates motility of EHEC O157:H7 directly as well as indirectly by controlling the transcription of qseBC.
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Affiliation(s)
- Vijay K. Sharma
- Food Safety and Enteric Pathogens Research Unit, United States Department of Agriculture, Agricultural Research Service, National Animal Disease Center, Ames, Iowa, United States of America
- * E-mail:
| | - Thomas A. Casey
- Food Safety and Enteric Pathogens Research Unit, United States Department of Agriculture, Agricultural Research Service, National Animal Disease Center, Ames, Iowa, United States of America
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Hong S, Cha I, Kim NO, Kim SH, Jung KT, Lee JH, Kim DW, Park MS, Kang YH. Enhanced Type III Secretion System Expression of Atypical Shigella flexneri II:(3)4,7(8). Osong Public Health Res Perspect 2013; 3:222-8. [PMID: 24159518 PMCID: PMC3747661 DOI: 10.1016/j.phrp.2012.10.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2012] [Revised: 09/26/2012] [Accepted: 10/02/2012] [Indexed: 10/27/2022] Open
Abstract
OBJECTIVES We aimed at evaluating the virulence of atypical Shigella flexneri II:(3)4,7(8) by DNA microarray and invasion assay. METHODS We used a customized S. flexneri DNA microarray to analyze an atypical S. flexneri II:(3)4,7(8) gene expression profile and compared it with that of the S. flexneri 2b strain. RESULTS Approximately one-quarter of the atypical S. flexneri II:(3)4,7(8) strain genes showed significantly altered expression profiles; 344 genes were more than two-fold upregulated, and 442 genes were more than 0.5-fold downregulated. The upregulated genes were divided into the category of 21 clusters of orthologous groups (COGs), and the "not in COGs" category included 170 genes. This category had virulence plasmid genes, including the ipa-mxi-spa genes required for invasion of colorectal epithelium (type III secretion system). Quantitative reverse-transcription polymerase chain reaction results also showed the same pattern in two more atypical S. flexneri II:(3)4,7(8) strains. Atypical S. flexneri II:(3)4,7(8) showed four times increased invasion activity in Caco-2 cells than that of typical strains. CONCLUSION Our results provide the intracellularly regulated genes that may be important for adaptation and growth strategies of this atypical S. flexneri.
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Affiliation(s)
- Sahyun Hong
- Division of Enteric Bacterial Infections, Korea National Institute of Health, Osong, Korea
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Structure of GrlR–GrlA complex that prevents GrlA activation of virulence genes. Nat Commun 2013; 4:2546. [DOI: 10.1038/ncomms3546] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2013] [Accepted: 09/03/2013] [Indexed: 12/27/2022] Open
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Morgan JK, Vendura KW, Stevens SM, Riordan JT. RcsB determines the locus of enterocyte effacement (LEE) expression and adherence phenotype of Escherichia coli O157 : H7 spinach outbreak strain TW14359 and coordinates bicarbonate-dependent LEE activation with repression of motility. MICROBIOLOGY-SGM 2013; 159:2342-2353. [PMID: 23985143 DOI: 10.1099/mic.0.070201-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The 2006 US spinach outbreak of Escherichia coli O157 : H7, characterized by unusually severe disease, has been attributed to a strain (TW14359) with enhanced pathogenic potential, including elevated virulence gene expression, robust adherence and the presence of novel virulence factors. This study proposes a mechanism for the unique virulence expression and adherence phenotype of this strain, and further expands the role for regulator RcsB in control of the E. coli locus of enterocyte effacement (LEE) pathogenicity island. Proteomic analysis of TW14359 revealed a virulence proteome consistent with previous transcriptome studies that included elevated levels of the LEE regulatory protein Ler and type III secretion system (T3SS) proteins, secreted T3SS effectors and Shiga toxin 2. Basal levels of the LEE activator and Rcs phosphorelay response regulator, RcsB, were increased in strain TW14359 relative to O157 : H7 strain Sakai. Deletion of rcsB eliminated inherent differences between these strains in ler expression, and in T3SS-dependent adherence. A reciprocating regulatory pathway involving RcsB and LEE-encoded activator GrlA was identified and predicted to co-ordinate LEE activation with repression of the flhDC flagellar regulator and motility. Overexpression of grlA was shown to increase RcsB levels, but did not alter expression from promoters driving rcsB transcription. Expression of rcsDB and RcsB was determined to increase in response to physiological levels of bicarbonate, and bicarbonate-dependent stimulation of the LEE was shown to be dependent on an intact Rcs system and ler activator grvA. The results of this study significantly broaden the role for RcsB in enterohaemorrhagic E. coli virulence regulation.
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Affiliation(s)
- Jason K Morgan
- Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida, Tampa, FL 33620, USA
| | - Khoury W Vendura
- Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida, Tampa, FL 33620, USA
| | - Stanley M Stevens
- Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida, Tampa, FL 33620, USA
| | - James T Riordan
- Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida, Tampa, FL 33620, USA
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Steinmann R, Dersch P. Thermosensing to adjust bacterial virulence in a fluctuating environment. Future Microbiol 2013; 8:85-105. [PMID: 23252495 DOI: 10.2217/fmb.12.129] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The lifecycle of most microbial pathogens can be divided into two states: existence outside and inside their hosts. The sudden temperature upshift experienced upon entry from environmental or vector reservoirs into a warm-blooded host is one of the most crucial signals informing the pathogens to adjust virulence gene expression and their host-stress survival program. This article reviews the plethora of sophisticated strategies that bacteria have evolved to sense temperature, and outlines the molecular signal transduction mechanisms used to modulate synthesis of crucial virulence determinants. The molecular details of thermal control through conformational changes of DNA, RNA and proteins are summarized, complex and diverse thermosensing principles are introduced and their potential as drug targets or synthetic tools are discussed.
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Affiliation(s)
- Rebekka Steinmann
- Department of Molecular Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
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A distinct regulatory sequence is essential for the expression of a subset of nle genes in attaching and effacing Escherichia coli. J Bacteriol 2012; 194:5589-603. [PMID: 22904277 DOI: 10.1128/jb.00190-12] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Enteropathogenic Escherichia coli uses a type III secretion system (T3SS), encoded in the locus of enterocyte effacement (LEE) pathogenicity island, to translocate a wide repertoire of effector proteins into the host cell in order to subvert cell signaling cascades and promote bacterial colonization and survival. Genes encoding type III-secreted effectors are located in the LEE and scattered throughout the chromosome. While LEE gene regulation is better understood, the conditions and factors involved in the expression of effectors encoded outside the LEE are just starting to be elucidated. Here, we identified a highly conserved sequence containing a 13-bp inverted repeat (IR), located upstream of a subset of genes coding for different non-LEE-encoded effectors in A/E pathogens. Site-directed mutagenesis and deletion analysis of the nleH1 and nleB2 regulatory regions revealed that this IR is essential for the transcriptional activation of both genes. Growth conditions that favor the expression of LEE genes also facilitate the activation of nleH1 and nleB2; however, their expression is independent of the LEE-encoded positive regulators Ler and GrlA but is repressed by GrlR and the global regulator H-NS. In contrast, GrlA and Ler are required for nleA expression, while H-NS silences it. Consistent with their role in the regulation of nleA, purified Ler and H-NS bound to the regulatory region of nleA upstream of its promoter. This work shows that at least two modes of regulation control the expression of effector genes in attaching and effacing (A/E) pathogens, suggesting that a subset of effector functions may be coordinately expressed in a particular niche or time during infection.
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Mutations that impact the enteropathogenic Escherichia coli Cpx envelope stress response attenuate virulence in Galleria mellonella. Infect Immun 2012; 80:3077-85. [PMID: 22710873 DOI: 10.1128/iai.00081-12] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In this paper, we show that the larvae of the greater wax moth, Galleria mellonella, can be used as a model to study enteropathogenic Escherichia coli (EPEC) virulence. G. mellonella larvae are killed after infection with EPEC type strain E2348/69 but not by an attenuated derivative that expresses diminished levels of the major virulence determinants or by a mutant specifically defective in type III secretion (T3S). Infecting EPEC inhabit the larval hemocoel only briefly and then become localized to melanized capsules, where they remain extracellular. Previously, it was shown that mutations affecting the Cpx envelope stress response lead to diminished expression of the bundle-forming pilus (BFP) and the type III secretion system (T3SS). We demonstrate that mutations that activate the Cpx pathway have a dramatic effect on the ability of the bacterium to establish a lethal infection, and this is correlated with an inability to grow in vivo. Infection with all E. coli strains led to increased expression of the antimicrobial peptides (AMPs) gloverin and cecropin, although strain- and AMP-specific differences were observed, suggesting that the G. mellonella host perceives attenuated strains and Cpx mutants in unique manners. Overall, this study shows that G. mellonella is an economical, alternative infection model for the preliminary study of EPEC host-pathogen interactions, and that induction of the Cpx envelope stress response leads to defects in virulence.
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Jeong JH, Kim HJ, Kim KH, Shin M, Hong Y, Rhee JH, Schneider TD, Choy HE. An unusual feature associated with LEE1 P1 promoters in enteropathogenic Escherichia coli (EPEC). Mol Microbiol 2012; 83:612-22. [PMID: 22229878 DOI: 10.1111/j.1365-2958.2011.07956.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Transcription start points in bacteria are influenced by the nature of the RNA polymerase·promoter interaction. For Escherichia coli RNA polymerase holoenzyme containing σ70, it is presumed that specific sequence in one or more of the -10, extended -10 and -35 elements of the promoter guides the RNAP to select the cognate start point. Here, we investigated the promoter driving expression of the LEE1 operon in enteropathogenic E. coli and found two promoters separated by 10 bp, LEE1 P1A (+1) and LEE1 P1B (+10) using various in vitro biochemical tools. A unique feature of P1B was the presence of multiple transcription starts from five neighbouring As at the initial transcribed region. The multiple products did not arise from stuttering synthesis. Analytical software based on information theory was employed to determine promoter elements. The concentration of the NTP pool altered the preferred transcription start points, albeit the underlying mechanism is elusive. Under in vivo conditions, dominant P1B, but not P1A, was subject to regulation by IHF.
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Affiliation(s)
- Jae-Ho Jeong
- Center for Host Defense against Enteropathogenic Bacteria Infection, Department of Microbiology, Chonnam National University Medical School, Kwangju, South Korea
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Cordeiro TN, Schmidt H, Madrid C, Juárez A, Bernadó P, Griesinger C, García J, Pons M. Indirect DNA readout by an H-NS related protein: structure of the DNA complex of the C-terminal domain of Ler. PLoS Pathog 2011; 7:e1002380. [PMID: 22114557 PMCID: PMC3219716 DOI: 10.1371/journal.ppat.1002380] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2011] [Accepted: 09/30/2011] [Indexed: 11/22/2022] Open
Abstract
Ler, a member of the H-NS protein family, is the master regulator of the LEE pathogenicity island in virulent Escherichia coli strains. Here, we determined the structure of a complex between the DNA-binding domain of Ler (CT-Ler) and a 15-mer DNA duplex. CT-Ler recognizes a preexisting structural pattern in the DNA minor groove formed by two consecutive regions which are narrower and wider, respectively, compared with standard B-DNA. The compressed region, associated with an AT-tract, is sensed by the side chain of Arg90, whose mutation abolishes the capacity of Ler to bind DNA. The expanded groove allows the approach of the loop in which Arg90 is located. This is the first report of an experimental structure of a DNA complex that includes a protein belonging to the H-NS family. The indirect readout mechanism not only explains the capacity of H-NS and other H-NS family members to modulate the expression of a large number of genes but also the origin of the specificity displayed by Ler. Our results point to a general mechanism by which horizontally acquired genes may be specifically recognized by members of the H-NS family. Pathogenic Escherichia coli strains and other enterobacteria carry genes acquired from other bacteria by a process known as horizontal gene transfer. Proper regulation of the genes that are expressed in a given moment is crucial for the success of the bacteria. The protein H-NS is a global regulator that binds DNA and maintains a large number of genes silent until they are required, for example, to sustain the bacteria's colonization of a new host. Ler is a member of the H-NS family that competes with H-NS to activate the expression of a group of horizontally acquired genes that encode for a molecular machine used by E. coli to infect human cells. Ler and H-NS share a similar DNA-binding domain and can bind to different DNA sequences. Here, we present the structure of a complex between the DNA-binding domain of Ler and a natural DNA fragment. This structure reveals that Ler recognizes specific DNA shapes, explaining its capacity to regulate genes with different sequences. A single arginine residue is key for the recognition of a DNA narrow minor groove, which is one of, though not the only, hallmarks of the DNA shapes that are recognized by H-NS and Ler.
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Affiliation(s)
- Tiago N. Cordeiro
- Institute for Research in Biomedicine (IRB Barcelona), Parc Científic de Barcelona, Barcelona, Spain
| | - Holger Schmidt
- Max Planck Institute for Biophysical Chemistry, Department of NMR-based Structural Biology, Göttingen, Germany
| | - Cristina Madrid
- Department of Microbiology, University of Barcelona, Barcelona, Spain
| | - Antonio Juárez
- Department of Microbiology, University of Barcelona, Barcelona, Spain
- Institut de Bioenginyeria de Catalunya (IBEC), Parc Científic de Barcelona, Barcelona, Spain
| | - Pau Bernadó
- Institute for Research in Biomedicine (IRB Barcelona), Parc Científic de Barcelona, Barcelona, Spain
| | - Christian Griesinger
- Max Planck Institute for Biophysical Chemistry, Department of NMR-based Structural Biology, Göttingen, Germany
| | - Jesús García
- Institute for Research in Biomedicine (IRB Barcelona), Parc Científic de Barcelona, Barcelona, Spain
- * E-mail: (MP); (JG)
| | - Miquel Pons
- Institute for Research in Biomedicine (IRB Barcelona), Parc Científic de Barcelona, Barcelona, Spain
- Department of Organic Chemistry, University of Barcelona, Barcelona, Spain
- * E-mail: (MP); (JG)
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Hfq virulence regulation in enterohemorrhagic Escherichia coli O157:H7 strain 86-24. J Bacteriol 2011; 193:6843-51. [PMID: 21984790 DOI: 10.1128/jb.06141-11] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Enterohemorrhagic Escherichia coli O157:H7 (EHEC) causes bloody diarrhea and hemolytic-uremic syndrome. EHEC encodes the sRNA chaperone Hfq, which is important in posttranscriptional regulation. In EHEC strain EDL933, Hfq acts as a negative regulator of the locus of enterocyte effacement (LEE), which encodes most of the proteins involved in type III secretion and attaching and effacing (AE) lesions. Here, we deleted hfq in the EHEC strain 86-24 and compared global transcription profiles of the hfq mutant and wild-type (WT) strains in exponential growth phase. Deletion of hfq affected transcription of genes common to nonpathogenic and pathogenic strains of E. coli as well as pathogen-specific genes. Downregulated genes in the hfq mutant included ler, the transcriptional activator of all the LEE genes, as well as genes encoded in the LEE2 to -5 operons. Decreased expression of the LEE genes in the hfq mutant occurred at middle, late, and stationary growth phases. We also confirmed decreased regulation of the LEE genes by examining the proteins secreted and AE lesion formation by the hfq mutant and WT strains. Deletion of hfq also caused decreased expression of the two-component system qseBC, which is involved in interkingdom signaling and virulence gene regulation in EHEC, as well as an increase in expression of stx(2AB), which encodes the deadly Shiga toxin. Altogether, these data indicate that Hfq plays a regulatory role in EHEC 86-24 that is different from what has been reported for EHEC strain EDL933 and that the role of Hfq in EHEC virulence regulation extends beyond the LEE.
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Cordone A, Lucchini S, Felice M, Ricca E. Direct and indirect control of Lrp on LEE pathogenicity genes of Citrobacter rodentium. FEMS Microbiol Lett 2011; 325:64-70. [DOI: 10.1111/j.1574-6968.2011.02411.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2011] [Revised: 07/11/2011] [Accepted: 09/05/2011] [Indexed: 11/29/2022] Open
Affiliation(s)
- Angelina Cordone
- Dipartimento di Biologia Strutturale e Funzionale; Università Federico II; Napoli; Italy
| | | | - Maurilio Felice
- Dipartimento di Biologia Strutturale e Funzionale; Università Federico II; Napoli; Italy
| | - Ezio Ricca
- Dipartimento di Biologia Strutturale e Funzionale; Università Federico II; Napoli; Italy
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Bustamante VH, Villalba MI, García-Angulo VA, Vázquez A, Martínez LC, Jiménez R, Puente JL. PerC and GrlA independently regulate Ler expression in enteropathogenic Escherichia coli. Mol Microbiol 2011; 82:398-415. [DOI: 10.1111/j.1365-2958.2011.07819.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Kitagawa R, Takaya A, Yamamoto T. Dual regulatory pathways of flagellar gene expression by ClpXP protease in enterohaemorrhagic Escherichia coli. MICROBIOLOGY-SGM 2011; 157:3094-3103. [PMID: 21903756 DOI: 10.1099/mic.0.051151-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
In enterobacteria such as Escherichia coli and Salmonella species, flagellar biogenesis is strictly dependent upon the master regulator flhDC. Here, we demonstrate that in enterohaemorrhagic E. coli (EHEC), the flagellar regulon is controlled by ClpXP, a member of the ATP-dependent protease family, through two pathways: (i) post-translational control of the FlhD/FlhC master regulator and (ii) transcriptional control of the flhDC operon. Both FlhD and FlhC proteins accumulated markedly following ClpXP depletion, and their half-lives were significantly longer in the mutant cells, suggesting that ClpXP is responsible for degrading FlhD and FlhC proteins, leading to downregulation of flagellar expression. ClpXP was involved in regulating the transcription of the flhD promoter only when the cells had entered stationary phase in a culture medium that markedly induced expression of the locus of enterocyte effacement (LEE). Comparative analyses of transcription from the flhD promoter in EHEC cells with different genetic backgrounds suggested that the downregulation of flhDC expression by ClpXP is dependent on the LEE-encoded GrlR-GrlA system. We have also shown that the degradation of FlhD and FlhC by ClpXP is responsible for downregulating flagellar expression even when LEE expression is induced.
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Affiliation(s)
- Ryo Kitagawa
- Department of Microbiology and Molecular Genetics, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba 263-8522, Japan
| | - Akiko Takaya
- Department of Microbiology and Molecular Genetics, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba 263-8522, Japan
| | - Tomoko Yamamoto
- Department of Microbiology and Molecular Genetics, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba 263-8522, Japan
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Coordinate control of the locus of enterocyte effacement and enterohemolysin genes by multiple common virulence regulators in enterohemorrhagic Escherichia coli. Infect Immun 2011; 79:4628-37. [PMID: 21844237 DOI: 10.1128/iai.05023-11] [Citation(s) in RCA: 15] [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 locus of enterocyte effacement (LEE) pathogenicity island is required for the intimate adhesion of enterohemorrhagic Escherichia coli (EHEC) to the intestinal epithelial cells. GrlR and GrlA are LEE-encoded negative and positive regulators, respectively. The interaction of these two regulators is important for controlling the transcription of LEE genes through Ler, a LEE-encoded central activator for the LEE. The GrlR-GrlA regulatory system controls not only LEE but also the expression of the flagellar and enterohemolysin (Ehx) genes in EHEC. Since Ehx levels were markedly induced in a grlR mutant but not in a grlR grlA double mutant and significantly increased by overexpression of GrlA in a ler mutant, GrlA is responsible for this regulation (T. Saitoh et al., J. Bacteriol. 190:4822-4830, 2008). In this study, additional investigations of the regulation of ehx gene expression determined that Ler also acts as an activator for Ehx expression without requiring GrlA function. We recently reported that the LysR-type regulator LrhA positively controls LEE expression (N. Honda et al., Mol. Microbiol. 74:1393-1411, 2009). The hemolytic activity of the lrhA mutant strain of EHEC was lower than that of the wild-type strain, and LrhA markedly induced ehx transcription in an E. coli K-12 strain, suggesting that LrhA also activates the transcription of ehx without GrlA and Ler. Gel mobility shift assays demonstrated that Ler and LrhA directly bind to the regulatory region of ehxC. Together, these results indicate that transcription of ehx is positively regulated by Ler, GrlA, and LrhA, which all act as positive regulators for LEE expression.
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CsrA and TnaB coregulate tryptophanase activity to promote exotoxin-induced killing of Caenorhabditis elegans by enteropathogenic Escherichia coli. J Bacteriol 2011; 193:4516-22. [PMID: 21705596 DOI: 10.1128/jb.05197-11] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Enteropathogenic Escherichia coli(EPEC) requires the tnaA-encoded enzyme tryptophanase and its substrate tryptophan to synthesize diffusible exotoxins that kill the nematode Caenorhabditis elegans. Here, we demonstrate that the RNA-binding protein CsrA and the tryptophan permease TnaB coregulate tryptophanase activity, through mutually exclusive pathways, to stimulate toxin-mediated paralysis and killing of C. elegans.
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Arvizu-Gómez JL, Hernández-Morales A, Pastor-Palacios G, Brieba LG, Álvarez-Morales A. Integration Host Factor (IHF) binds to the promoter region of the phtD operon involved in phaseolotoxin synthesis in P. syringae pv. phaseolicola NPS3121. BMC Microbiol 2011; 11:90. [PMID: 21542933 PMCID: PMC3112066 DOI: 10.1186/1471-2180-11-90] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2011] [Accepted: 05/04/2011] [Indexed: 11/24/2022] Open
Abstract
Background Pseudomonas syringae pv. phaseolicola, the causal agent of halo blight disease in beans, produces a toxin known as phaseolotoxin, in whose synthesis participate a group of genes organized within the genome in a region known as the "Pht cluster". This region, which is thought to have been acquired by horizontal gene transfer, includes 5 transcriptional units, two monocistronic (argK, phtL) and three polycistronic (phtA, phtD, phtM), whose expression is temperature dependent. So far, the regulatory mechanisms involved in phaseolotoxin synthesis have not been elucidated and the only well-established fact is the requirement of low temperatures for its synthesis. In this work, we searched for regulatory proteins that could be involved in phaseolotoxin synthesis, focusing on the regulation of the phtD operon. Results In this study we identified the global regulator IHF (Integration Host Factor), which binds to the promoter region of the phtD operon, exerting a negative effect on the expression of this operon. This is the first regulatory protein identified as part of the phaseolotoxin synthesis system. Our findings suggest that the Pht cluster was similarly regulated in the ancestral cluster by IHF or similar protein, and integrated into the global regulatory mechanism of P. syringae pv. phaseolicola, after the horizontal gene transfer event by using the host IHF protein. Conclusion This study identifies the IHF protein as one element involved in the regulation of phaseolotoxin synthesis in P. syringae pv. phaseolicola NPS3121 and provides new insights into the regulatory mechanisms involved in phaseolotoxin production.
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Affiliation(s)
- Jackeline Lizzeta Arvizu-Gómez
- Departamento de Ingeniería Genética, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional Unidad Irapuato, Apdo Postal 629, CP 36821, Irapuato, Gto, México
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Regulation of nleA in Shiga toxin-producing Escherichia coli O84:H4 strain 4795/97. J Bacteriol 2010; 193:832-41. [PMID: 21131485 DOI: 10.1128/jb.00582-10] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Many Shiga toxin-producing Escherichia coli (STEC) strains express a type III secretion system (TTSS) encoded by the locus of enterocyte effacement (LEE). Using the TTSS, STEC is able to inject effector proteins directly into eukaryotic host cells, where they cause characteristic attaching and effacing (A/E) lesions. In addition to the LEE-encoded effectors, a number of non-LEE-encoded effectors, located on phage-associated elements, have been described. One of them, the non-LEE-encoded effector A (NleA), is widely distributed among pathogenic E. coli. In this study, we investigated the influence of environmental conditions on the expression of the phage-encoded effector nleA gene (designated nleA(4795)) present in STEC O84:H4 strain 4795/97. We demonstrated that a particular NaCl concentration and starvation stress increase the activity of the nleA(4795) promoter. Moreover, several regulators that control nleA(4795) expression were identified. The involvement of the LEE regulators Ler, GrlA, and GrlR show that nleA(4795) is integrated in the LEE regulation circuit. Furthermore, the binding of Ler to sequences upstream of nleA(4795) underlined these findings.
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Boettcher JP, Kirchner M, Churin Y, Kaushansky A, Pompaiah M, Thorn H, Brinkmann V, MacBeath G, Meyer TF. Tyrosine-phosphorylated caveolin-1 blocks bacterial uptake by inducing Vav2-RhoA-mediated cytoskeletal rearrangements. PLoS Biol 2010; 8. [PMID: 20808760 PMCID: PMC2927421 DOI: 10.1371/journal.pbio.1000457] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2009] [Accepted: 07/07/2010] [Indexed: 12/11/2022] Open
Abstract
During the early stages of infection, Neisseria gonorrhoeae triggers a phosphotyrosine-dependent Cav1-Vav2-RhoA signaling cascade that promotes the pathogen's extracellular state. Certain bacterial adhesins appear to promote a pathogen's extracellular lifestyle rather than its entry into host cells. However, little is known about the stimuli elicited upon such pathogen host-cell interactions. Here, we report that type IV pili (Tfp)-producing Neisseria gonorrhoeae (P+GC) induces an immediate recruitment of caveolin-1 (Cav1) in the host cell, which subsequently prevents bacterial internalization by triggering cytoskeletal rearrangements via downstream phosphotyrosine signaling. A broad and unbiased analysis of potential interaction partners for tyrosine-phosphorylated Cav1 revealed a direct interaction with the Rho-family guanine nucleotide exchange factor Vav2. Both Vav2 and its substrate, the small GTPase RhoA, were found to play a direct role in the Cav1-mediated prevention of bacterial uptake. Our findings, which have been extended to enteropathogenic Escherichia coli, highlight how Tfp-producing bacteria avoid host cell uptake. Further, our data establish a mechanistic link between Cav1 phosphorylation and pathogen-induced cytoskeleton reorganization and advance our understanding of caveolin function. Like many bacterial pathogens, successful attachment of Neisseria gonorrhoeae—the causative agent of the sexually transmitted disease gonorrhoea—to its host cells depends on specialized structures on the bacterial surface called type IV pili (Tfp). Pathogen attachment induces changes within host cells that may facilitate and promote infection. In this study, we identify some of the earliest cellular signals elicited by N. gonorrhoeae during infection, which, in this case, prevent the organism from entering the cell precociously. After attachment to host cells the bacteria form microcolonies on the cell surface. Underneath these microcolonies, so-called cortical plaques form within the host cell—these contain the cytoskeleton protein actin and a range of signaling proteins. We show that N. gonorrhoeae recruits a host cell protein called caveolin-1 to the cell membrane where the bacteria are attached; here, caveloin-1 effectively impedes uptake of the bacteria by activating a signaling cascade that involves its phosphorylation on a tyrosine residue and subsequent interactions with proteins that regulate the cytoskeleton. Thus, these proteins play a pivotal role in maintaining N. gonorrhoeae in the extracellular milieu. By extrapolating our findings to another Tfp-producing bacterium, the enteropathogenic Escherichia coli, we argue that the establishment and maintenance of this extracellular state benefits certain pathogens by giving them time to express proteins required for subsequent steps of infection.
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Affiliation(s)
- Jan Peter Boettcher
- Department of Molecular Biology, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Marieluise Kirchner
- Department of Molecular Biology, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Yuri Churin
- Department of Molecular Biology, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Alexis Kaushansky
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts, United States of America
| | - Malvika Pompaiah
- Department of Molecular Biology, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Hans Thorn
- Department of Molecular Biology, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Volker Brinkmann
- Department of Molecular Biology, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Gavin MacBeath
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts, United States of America
| | - Thomas F. Meyer
- Department of Molecular Biology, Max Planck Institute for Infection Biology, Berlin, Germany
- * E-mail:
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Molecular characterization of GrlA, a specific positive regulator of ler expression in enteropathogenic Escherichia coli. J Bacteriol 2010; 192:4627-42. [PMID: 20622062 DOI: 10.1128/jb.00307-10] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Enteropathogenic Escherichia coli (EPEC) infections are characterized by the formation of attaching and effacing (A/E) lesions on the surfaces of infected epithelial cells. The genes required for the formation of A/E lesions are located within the locus of enterocyte effacement (LEE). Ler is the key regulatory factor controlling the expression of LEE genes. Expression of the ler gene is positively regulated by GrlA, which is encoded by the LEE. Here, we analyze the mechanism by which GrlA positively regulates ler expression and show that in the absence of H-NS, GrlA is no longer essential for ler activation, further confirming that GrlA acts in part as an H-NS antagonist on the ler promoter. Single-amino-acid mutants were constructed to test the functional significance of the putative helix-turn-helix (HTH) DNA binding motif found in the N-terminal half of GrlA, as well as at the C-terminal domain of the protein. Several mutations within the HTH motif, but not all, completely abolished GrlA activity, as well as specific binding to its target sequence downstream from position -54 in the ler regulatory region. Some of these mutants, albeit inactive, were still able to interact with the negative regulator GrlR, indicating that loss of activity was not a consequence of protein misfolding. Additional residues in the vicinity of the HTH domain, as well as at the end of the protein, were also shown to be important for GrlA activity as a transcriptional regulator, but not for its interaction with GrlR. In summary, GrlA consists of at least two functional domains, one involved in transcriptional activation and DNA binding and the other in heterodimerization with GrlR.
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The LysR-type transcriptional regulator QseD alters type three secretion in enterohemorrhagic Escherichia coli and motility in K-12 Escherichia coli. J Bacteriol 2010; 192:3699-712. [PMID: 20494990 DOI: 10.1128/jb.00382-10] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Enterohemorrhagic Escherichia coli (EHEC) O157:H7 responds to the host-produced epinephrine and norepinephrine, and bacterially produced autoinducer 3 (AI-3), through two-component systems. Further integration of multiple regulatory signaling networks, involving regulators such as the LysR-type transcriptional regulator (LTTR) QseA, promotes effective regulation of virulence factors. These include the production of flagella, a phage-encoded Shiga toxin, and genes within the locus of enterocyte effacement (LEE) responsible for attaching and effacing (AE) lesion formation. Here, we describe a new member of this signaling cascade, an LTTR heretofore renamed QseD (quorum-sensing E. coli regulator D). QseD is present in all enterobacteria but exists almost exclusively in O157:H7 isolates as a helix-turn-helix (HTH) truncated isoform. This "short" isoform (sQseD) is still able to regulate gene expression through a different mechanism than the full-length K-12 E. coli "long" QseD isoform (lQseD). The EHEC Delta qseD mutant exhibits increased expression of all LEE operons and deregulation of AE lesion formation. The loss of qseD in EHEC does not affect motility, but the K-12 Delta qseD mutant is hypermotile. While the lQseD directly binds to the ler promoter, encoding the LEE master regulator, to repress LEE transcription, the sQseD isoform does not. LTTRs bind to DNA as tetramers, and these data suggest that sQseD regulates ler by forming heterotetramers with another LTTR. The LTTRs known to regulate LEE transcription, QseA and LrhA, do not interact with sQseD, suggesting that sQseD acts as a dominant-negative partner with a yet-unidentified LTTR.
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Transcriptional analysis of the grlRA virulence operon from Citrobacter rodentium. J Bacteriol 2010; 192:3722-34. [PMID: 20472788 DOI: 10.1128/jb.01540-09] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The locus for enterocyte effacement (LEE) is the virulence hallmark of the attaching-and-effacing (A/E) intestinal pathogens, namely, enteropathogenic Escherichia coli, enterohemorrhagic E. coli, and Citrobacter rodentium. The LEE carries more than 40 genes that are arranged in several operons, e.g., LEE1 to LEE5. Expression of the various transcriptional units is subject to xenogeneic silencing by the histone-like protein H-NS. The LEE1-encoded regulator, Ler, plays a key role in relieving this repression at several major LEE promoters, including LEE2 to LEE5. To achieve appropriate intracellular concentrations of Ler in different environments, A/E pathogens have evolved a sophisticated regulatory network to control ler expression. For example, the LEE-encoded GrlA and GrlR proteins work as activator and antiactivator, respectively, of ler transcription. Thus, control of the transcriptional activities of the LEE1 (ler) promoter and the grlRA operon determines the rate of transcription of all of the LEE-encoded virulence factors. To date, only a single promoter has been identified for the grlRA operon. In this study, we showed that the non-LEE-encoded AraC-like regulatory protein RegA of C. rodentium directly stimulates transcription of the grlRA promoter by binding to an upstream region in the presence of bicarbonate ions. In addition, in vivo and in vitro transcription assays revealed a sigma(70) promoter that is specifically responsible for transcription of grlA. Expression from this promoter was strongly repressed by H-NS and its paralog StpA but was activated by Ler. DNase I footprinting demonstrated that Ler binds to a region upstream of the grlA promoter, whereas H-NS interacts specifically with a region extending from the grlA core promoter into its coding sequence. Together, these findings provide new insights into the environmental regulation and differential expressions of the grlR and grlA genes of C. rodentium.
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Kendall MM, Rasko DA, Sperandio V. The LysR-type regulator QseA regulates both characterized and putative virulence genes in enterohaemorrhagic Escherichia coli O157:H7. Mol Microbiol 2010; 76:1306-21. [PMID: 20444105 DOI: 10.1111/j.1365-2958.2010.07174.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Enterohaemorrhagic Escherichia coli (EHEC) colonizes the large intestine, causing attaching and effacing (AE) lesions. Most of the genes involved in AE lesion formation are encoded within a chromosomal pathogenicity island termed the locus of enterocyte effacement (LEE). The LysR-type transcriptional factor QseA regulates the LEE by binding to the regulatory region of ler. We performed transcriptome analyses comparing wild-type (WT) EHEC and the qseA mutant to elucidate QseA's role in gene regulation. During both growth phases, several genes carried in O-islands were activated by QseA, whereas genes involved in cell metabolism were repressed. During late-logarithmic growth, QseA activated expression of the LEE genes as well as non-LEE-encoded effector proteins. We also performed electrophoretic mobility shift assays, competition experiments and DNase I footprints. The results demonstrated that QseA directly binds both the ler proximal and distal promoters, its own promoter, as well as promoters of genes encoded in EHEC-specific O-islands. Additionally, we mapped the transcriptional start site of qseA, leading to the identification of two promoter sequences. Taken together, these results indicate that QseA acts as a global regulator in EHEC, co-ordinating expression of virulence genes.
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Affiliation(s)
- Melissa M Kendall
- University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Blvd., Dallas, TX 75390-9048, USA
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Abu-Ali GS, Ouellette LM, Henderson ST, Lacher DW, Riordan JT, Whittam TS, Manning SD. Increased adherence and expression of virulence genes in a lineage of Escherichia coli O157:H7 commonly associated with human infections. PLoS One 2010; 5:e10167. [PMID: 20422047 PMCID: PMC2858043 DOI: 10.1371/journal.pone.0010167] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2010] [Accepted: 03/22/2010] [Indexed: 11/23/2022] Open
Abstract
BACKGROUND Enterohemorrhagic Escherichia coli (EHEC) O157:H7, a food and waterborne pathogen, can be classified into nine phylogenetically distinct lineages, as determined by single nucleotide polymorphism genotyping. One lineage (clade 8) was found to be associated with hemolytic uremic syndrome (HUS), which can lead to kidney failure and death in some cases, particularly young children. Another lineage (clade 2) differs considerably in gene content and is phylogenetically distinct from clade 8, but caused significantly fewer cases of HUS in a prior study. Little is known, however, about how these two lineages vary with regard to phenotypic traits important for disease pathogenesis and in the expression of shared virulence genes. METHODOLOGY/PRINCIPAL FINDINGS Here, we quantified the level of adherence to and invasion of MAC-T bovine epithelial cells, and examined the transcriptomes of 24 EHEC O157:H7 strains with varying Shiga toxin profiles from two common lineages. Adherence to epithelial cells was >2-fold higher for EHEC O157:H7 strains belonging to clade 8 versus clade 2, while no difference in invasiveness was observed between the two lineages. Whole-genome 70-mer oligo microarrays, which probe for 6088 genes from O157:H7 Sakai, O157:H7 EDL 933, pO157, and K12 MG1655, detected significant differential expression between clades in 604 genes following co-incubation with epithelial cells for 30 min; 186 of the 604 genes had a >1.5 fold change difference. Relative to clade 2, clade 8 strains showed upregulation of major virulence genes, including 29 of the 41 locus of enterocyte effacement (LEE) pathogenicity island genes, which are critical for adherence, as well as Shiga toxin genes and pO157 plasmid-encoded virulence genes. Differences in expression of 16 genes that encode colonization factors, toxins, and regulators were confirmed by qRT-PCR, which revealed a greater magnitude of change than microarrays. CONCLUSIONS/SIGNIFICANCE These findings demonstrate that the EHEC O157:H7 lineage associated with HUS expresses higher levels of virulence genes and has an enhanced ability to attach to epithelial cells relative to another common lineage.
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Affiliation(s)
- Galeb S. Abu-Ali
- Microbial Evolution Laboratory, National Food Safety & Toxicology Center, Michigan State University, East Lansing, Michigan, United States of America
| | - Lindsey M. Ouellette
- Microbial Evolution Laboratory, National Food Safety & Toxicology Center, Michigan State University, East Lansing, Michigan, United States of America
| | - Scott T. Henderson
- Microbial Evolution Laboratory, National Food Safety & Toxicology Center, Michigan State University, East Lansing, Michigan, United States of America
| | - David W. Lacher
- Division of Molecular Biology, Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, Laurel, Maryland, United States of America
| | - James T. Riordan
- Microbial Evolution Laboratory, National Food Safety & Toxicology Center, Michigan State University, East Lansing, Michigan, United States of America
| | - Thomas S. Whittam
- Microbial Evolution Laboratory, National Food Safety & Toxicology Center, Michigan State University, East Lansing, Michigan, United States of America
| | - Shannon D. Manning
- Microbial Evolution Laboratory, National Food Safety & Toxicology Center, Michigan State University, East Lansing, Michigan, United States of America
- Department of Pediatrics and Human Development, Michigan State University, East Lansing, Michigan, United States of America
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Arnold R, Jehl A, Rattei T. Targeting effectors: the molecular recognition of Type III secreted proteins. Microbes Infect 2010; 12:346-58. [PMID: 20178857 DOI: 10.1016/j.micinf.2010.02.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2010] [Accepted: 02/10/2010] [Indexed: 01/01/2023]
Abstract
The Type III secretion system (TTSS) facilitates the export of effector proteins from pathogenic and symbiotic Gram-negative bacteria into the cytosol of eukaryotic host cells. The current functional and evolutionary knowledge on the molecular recognition of TTSS substrates and computational models of the secretion signal are discussed in this review.
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Affiliation(s)
- Roland Arnold
- Department of Genome Oriented Bioinformatics, Technische Universität München, Wissenschaftszentrum Weihenstephan, 85350 Freising, Germany
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