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Hernandez-Doria JD, Sperandio V. Bacteriophage Transcription Factor Cro Regulates Virulence Gene Expression in Enterohemorrhagic Escherichia coli. Cell Host Microbe 2018; 23:607-617.e6. [PMID: 29746832 DOI: 10.1016/j.chom.2018.04.007] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Revised: 02/15/2018] [Accepted: 04/16/2018] [Indexed: 10/16/2022]
Abstract
Bacteriophage-encoded genetic elements control bacterial biological functions. Enterohemorrhagic Escherichia coli (EHEC) strains harbor lambda-phages encoding the Shiga-toxin (Stx), which is expressed during the phage lytic cycle and associated with exacerbated disease. Phages also reside dormant within bacterial chromosomes through their lysogenic cycle, but how this impacts EHEC virulence remains unknown. We find that during lysogeny the phage transcription factor Cro activates the EHEC type III secretion system (T3SS). EHEC lambdoid phages are lysogenic under anaerobic conditions when Cro binds to and activates the promoters of T3SS genes. Interestingly, the Cro sequence varies among phages carried by different EHEC outbreak strains, and these changes affect Cro-dependent T3SS regulation. Additionally, infecting mice with the related pathogen C. rodentium harboring the bacteriophage cro from EHEC results in greater T3SS gene expression and enhanced virulence. Collectively, these findings reveal the role of phages in impacting EHEC virulence and their potential to affect outbreak strains.
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Affiliation(s)
- Juan D Hernandez-Doria
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9048, USA; Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390-9048, USA
| | - Vanessa Sperandio
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9048, USA; Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390-9048, USA.
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García-Pastor L, Sánchez-Romero MA, Gutiérrez G, Puerta-Fernández E, Casadesús J. Formation of phenotypic lineages in Salmonella enterica by a pleiotropic fimbrial switch. PLoS Genet 2018; 14:e1007677. [PMID: 30252837 PMCID: PMC6173445 DOI: 10.1371/journal.pgen.1007677] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Revised: 10/05/2018] [Accepted: 09/05/2018] [Indexed: 11/29/2022] Open
Abstract
The std locus of Salmonella enterica, an operon acquired by horizontal transfer, encodes fimbriae that permit adhesion to epithelial cells in the large intestine. Expression of the std operon is bistable, yielding a major subpopulation of StdOFF cells (99.7%) and a minor subpopulation of StdON cells (0.3%). In addition to fimbrial proteins, the std operon encodes two proteins, StdE and StdF, that have DNA binding capacity and control transcription of loci involved in flagellar synthesis, chemotaxis, virulence, conjugal transfer, biofilm formation, and other cellular functions. As a consequence of StdEF pleiotropic transcriptional control, StdON and StdOFF subpopulations may differ not only in the presence or absence of Std fimbriae but also in additional phenotypic traits. Separation of StdOFF and StdON lineages by cell sorting confirms the occurrence of lineage-specific features. Formation of StdOFF and StdON lineages may thus be viewed as a rudimentary bacterial differentiation program. We show that the std fimbrial operon of Salmonella enterica undergoes bistable expression, a trait far from exceptional among loci that encode components of the bacterial envelope. However, an unsuspected trait of the std operon is the presence of two genes that encode pleiotropic regulators of gene expression. Indeed, StdE and StdF are DNA-binding proteins that control transcription of hundreds of genes. As a consequence, StdEF govern multiple phenotypic traits, and the fimbriated and non-fimbriated Salmonella lineages may differ in motility, virulence, conjugal transfer, biofilm formation, and potentially in other phenotypic features. We hypothesize that pleiotropic control of gene expression by StdEF may contribute to adapt the non-fimbriated lineage to acute infection and the fimbriated lineage to chronic infection.
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Affiliation(s)
- Lucía García-Pastor
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain
| | | | - Gabriel Gutiérrez
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain
| | - Elena Puerta-Fernández
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain
- Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS, CSIC), Sevilla, Spain
- * E-mail: (EPF); (JC)
| | - Josep Casadesús
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain
- * E-mail: (EPF); (JC)
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Xiaoli L, Figler HM, Goswami Banerjee K, Hayes CS, Dudley EG. Non-pathogenic Escherichia coli Enhance Stx2a Production of E. coli O157:H7 Through Both bamA-Dependent and Independent Mechanisms. Front Microbiol 2018; 9:1325. [PMID: 29973923 PMCID: PMC6020778 DOI: 10.3389/fmicb.2018.01325] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Accepted: 05/30/2018] [Indexed: 01/14/2023] Open
Abstract
Intestinal colonization by the foodborne pathogen Escherichia coli O157:H7 leads to serious disease symptoms, including hemolytic uremic syndrome (HUS) and hemorrhagic colitis (HC). Synthesis of one or more Shiga toxins (Stx) is essential for HUS and HC development. The genes encoding Stx, including Stx2a, are found within a lambdoid prophage integrated in the E. coli O157:H7 chromosome. Enhanced Stx2a expression was reported when specific non-pathogenic E. coli strains were co-cultured with E. coli O157:H7, and it was hypothesized that this phenotype required the non-pathogenic E. coli to be sensitive to stx-converting phage infection. We tested this hypothesis by generating phage resistant non-pathogenic E. coli strains where bamA (an essential gene and Stx phage receptor) was replaced with an ortholog from other species. Such heterologous gene replacement abolished the ability of the laboratory strain E. coli C600 to enhance toxin production when co-cultured with E. coli O157:H7 strain PA2, which belongs to the hypervirulent clade 8. The extracellular loops of BamA (loop 4, 6, 7) were further shown to be important for infection by stx2a-converting phages. However, similar gene replacement in another commensal E. coli, designated 1.1954, revealed a bamA-independent mechanism for toxin amplification. Toxin enhancement by 1.1954 was not the result of phage infection through an alternative receptor (LamB or FadL), lysogen formation by stx2a-converting phages, or the production of a secreted molecule. Collectively, these data suggest that non-pathogenic E. coli can enhance toxin production through at least two mechanisms.
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Affiliation(s)
- Lingzi Xiaoli
- Department of Food Science, The Pennsylvania State University, University Park, PA, United States
| | - Hillary M Figler
- Huck Institutes of Life Sciences, The Pennsylvania State University, University Park, PA, United States
| | - Kakolie Goswami Banerjee
- Department of Food Science, The Pennsylvania State University, University Park, PA, United States
| | - Christopher S Hayes
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Edward G Dudley
- Department of Food Science, The Pennsylvania State University, University Park, PA, United States.,Center for Immunology and Infectious Disease, The Pennsylvania State University, University Park, PA, United States
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Ding F, Allen V, Luo W, Zhang S, Duan Y. Molecular mechanisms underlying heat or tetracycline treatments for citrus HLB control. HORTICULTURE RESEARCH 2018; 5:30. [PMID: 29872535 PMCID: PMC5981314 DOI: 10.1038/s41438-018-0038-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Revised: 03/06/2018] [Accepted: 03/27/2018] [Indexed: 05/05/2023]
Abstract
Huanglongbing (HLB), a destructive plant bacterial disease, severely impedes worldwide citrus production. In our previous reports, we revealed the molecular mechanisms of host plant responses that underlie thermotherapy against HLB. In this study, we investigated the molecular mechanism underlying heat or tetracycline treatments on the HLB bacterium, 'Candidatus Liberibacter asiaticus' (Las) by focusing on Las prophage/phage conversion under stress conditions. By comparing the prophage FP1 and FP2 copy number to the copy number of 16S rDNA in HLB-affected plants, we found that the relative copy number of both FP1 and FP2 increased significantly, ranging from 3.4- to 6.7-fold change when Las-infected samples underwent a temperature shift from 23 to 37, 42 or 45 °C. When treated with tetracycline at 50-150 and 200-250 µg/ml, respectively, the relative copy number of both FP1 and FP2 increased by 3.4- to 6.0-fold. In addition, analyses of Las prophage structural gene and antirepressor gene copy numbers showed similar trends for all treatments. Furthermore, transmission electron microscopy provided direct evidence of lysogenic to lytic conversion upon temperature increase. These results not only provide new insight into the molecular mechanisms underlying heat or tetracycline treatment but also suggest a novel HLB control strategy by enhancing the endogenous conversion from Las prophages to phages.
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Affiliation(s)
- Fang Ding
- Hubei Key Laboratory of PLant Pathology, Huazhong Agricultural University, 430070 Wuhan, Hubei P.R. China
- USDA-ARS-USHRL, Fort Pierce, FL 34945 USA
| | | | - Weiqi Luo
- USDA-ARS-USHRL, Fort Pierce, FL 34945 USA
- Center for Integrated Pest Management, North Carolina State University, Raleigh, NC 27606 USA
| | - Shouan Zhang
- IFAS-TREC, University of Florida, Homestead, FL 33031 USA
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Górski A, Międzybrodzki R, Łobocka M, Głowacka-Rutkowska A, Bednarek A, Borysowski J, Jończyk-Matysiak E, Łusiak-Szelachowska M, Weber-Dąbrowska B, Bagińska N, Letkiewicz S, Dąbrowska K, Scheres J. Phage Therapy: What Have We Learned? Viruses 2018; 10:E288. [PMID: 29843391 PMCID: PMC6024844 DOI: 10.3390/v10060288] [Citation(s) in RCA: 82] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Revised: 05/11/2018] [Accepted: 05/22/2018] [Indexed: 02/07/2023] Open
Abstract
In this article we explain how current events in the field of phage therapy may positively influence its future development. We discuss the shift in position of the authorities, academia, media, non-governmental organizations, regulatory agencies, patients, and doctors which could enable further advances in the research and application of the therapy. In addition, we discuss methods to obtain optimal phage preparations and suggest the potential of novel applications of phage therapy extending beyond its anti-bacterial action.
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Affiliation(s)
- Andrzej Górski
- Bacteriophage Laboratory, Ludwik Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Rudolfa Weigla Street 12, 53-114 Wroclaw, Poland.
- Phage Therapy Unit, Ludwik Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Rudolfa Weigla Street 12, 53-114 Wroclaw, Poland.
- Department of Clinical Immunology, Transplantation Institute, Medical University of Warsaw, Nowogrodzka Street 59, 02-006 Warsaw, Poland.
| | - Ryszard Międzybrodzki
- Bacteriophage Laboratory, Ludwik Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Rudolfa Weigla Street 12, 53-114 Wroclaw, Poland.
- Phage Therapy Unit, Ludwik Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Rudolfa Weigla Street 12, 53-114 Wroclaw, Poland.
- Department of Clinical Immunology, Transplantation Institute, Medical University of Warsaw, Nowogrodzka Street 59, 02-006 Warsaw, Poland.
| | - Małgorzata Łobocka
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego Street 5 A, 02-106 Warsaw, Poland.
- Autonomous Department of Microbial Biology, Faculty of Agriculture and Biology, Warsaw University of Life Sciences, Nowoursynowska Street 159, 02-776 Warsaw, Poland.
| | - Aleksandra Głowacka-Rutkowska
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego Street 5 A, 02-106 Warsaw, Poland.
| | - Agnieszka Bednarek
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego Street 5 A, 02-106 Warsaw, Poland.
| | - Jan Borysowski
- Department of Clinical Immunology, Transplantation Institute, Medical University of Warsaw, Nowogrodzka Street 59, 02-006 Warsaw, Poland.
| | - Ewa Jończyk-Matysiak
- Bacteriophage Laboratory, Ludwik Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Rudolfa Weigla Street 12, 53-114 Wroclaw, Poland.
| | - Marzanna Łusiak-Szelachowska
- Bacteriophage Laboratory, Ludwik Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Rudolfa Weigla Street 12, 53-114 Wroclaw, Poland.
| | - Beata Weber-Dąbrowska
- Bacteriophage Laboratory, Ludwik Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Rudolfa Weigla Street 12, 53-114 Wroclaw, Poland.
- Phage Therapy Unit, Ludwik Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Rudolfa Weigla Street 12, 53-114 Wroclaw, Poland.
| | - Natalia Bagińska
- Bacteriophage Laboratory, Ludwik Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Rudolfa Weigla Street 12, 53-114 Wroclaw, Poland.
| | - Sławomir Letkiewicz
- Phage Therapy Unit, Ludwik Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Rudolfa Weigla Street 12, 53-114 Wroclaw, Poland.
- Medical Sciences Institute, Katowice School of Economics, Harcerzy Września Street 3, 40-659 Katowice, Poland.
| | - Krystyna Dąbrowska
- Bacteriophage Laboratory, Ludwik Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Rudolfa Weigla Street 12, 53-114 Wroclaw, Poland.
- Research and Development Center, Regional Specialized Hospital, Kamieńskiego 73a, 51-124 Wrocław, Poland.
| | - Jacques Scheres
- National Institute of Public Health NIZP, Chocimska Street 24, 00-971 Warsaw, Poland.
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Molecular Mechanisms Governing "Hair-Trigger" Induction of Shiga Toxin-Encoding Prophages. Viruses 2018; 10:v10050228. [PMID: 29710828 PMCID: PMC5977221 DOI: 10.3390/v10050228] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Revised: 04/25/2018] [Accepted: 04/25/2018] [Indexed: 01/12/2023] Open
Abstract
Shiga toxin (Stx)-encoding E. coli (STEC) strains are responsible for sporadic outbreaks of food poisoning dating to 1982, when the first STEC strain, E. coli O157:H7, was isolated. Regardless of STEC serotype, the primary symptoms of STEC infections are caused by Stx that is synthesized from genes resident on lambdoid prophage present in STEC. Despite similar etiology, the severity of STEC-mediated disease varies by outbreak. However, it is unclear what modulates the severity of STEC-mediated disease. Stx production and release is controlled by lytic growth of the Stx-encoding bacteriophage, which in turn, is controlled by the phage repressor. Here, we confirm our earlier suggestion that the higher spontaneous induction frequency of Stx-encoding prophage is a consequence, in part, of lower intracellular repressor levels in STEC strains versus non-STEC strains. We also show that this lowered intracellular repressor concentration is a consequence of the utilization of alternative binding/regulatory strategies by the phage repressor. We suggest that a higher spontaneous induction frequency would lead to increased virulence.
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Krüger A, Burgán J, Friedrich AW, Rossen JWA, Lucchesi PMA. ArgO145, a Stx2a prophage of a bovine O145:H- STEC strain, is closely related to phages of virulent human strains. INFECTION GENETICS AND EVOLUTION 2018; 60:126-132. [PMID: 29476813 DOI: 10.1016/j.meegid.2018.02.024] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Revised: 01/18/2018] [Accepted: 02/17/2018] [Indexed: 01/08/2023]
Abstract
Shiga toxins (Stx) are the main virulence factor of a pathogroup of Escherichia coli strains that cause severe human diseases. These toxins are encoded in prophages (Stx prophages), and generally their expression depends on prophage induction. Several studies have reported high diversity among both Stx prophages and Stx. In particular, the toxin subtype Stx2a is associated with high virulence and HUS. Here, we report the genome of ArgO145, an inducible Stx2a prophage identified in a bovine O145:H- strain which produced high levels of Shiga toxin and Stx phage particles. The ArgO145 genome shared lambda phage organization, with recombination, regulation, replication, lysis, and head and tail structural gene regions, although some lambda genes encoding regulatory proteins could not be identified. Remarkably, some Stx2a phages of strains isolated from patients in other countries showed high similarity to ArgO145.
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Affiliation(s)
- A Krüger
- Centro de Investigación Veterinaria de Tandil (CIVETAN), UNCPBA-CONICET-CIC, Laboratorio de Inmunoquímica y Biotecnología, Argentina.
| | - J Burgán
- Centro de Investigación Veterinaria de Tandil (CIVETAN), UNCPBA-CONICET-CIC, Laboratorio de Inmunoquímica y Biotecnología, Argentina
| | - A W Friedrich
- University of Groningen, University Medical Center Groningen, Department of Medical Microbiology, The Netherlands
| | - J W A Rossen
- University of Groningen, University Medical Center Groningen, Department of Medical Microbiology, The Netherlands
| | - P M A Lucchesi
- Centro de Investigación Veterinaria de Tandil (CIVETAN), UNCPBA-CONICET-CIC, Laboratorio de Inmunoquímica y Biotecnología, Argentina
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Kampmeier S, Berger M, Mellmann A, Karch H, Berger P. The 2011 German Enterohemorrhagic Escherichia Coli O104:H4 Outbreak-The Danger Is Still Out There. Curr Top Microbiol Immunol 2018; 416:117-148. [PMID: 30062592 DOI: 10.1007/82_2018_107] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Enterohemorrhagic Escherichia coli (EHEC) are Shiga toxin (Stx) producing bacteria causing a disease characterized by bloody (or non-bloody) diarrhea, which might progress to hemolytic uremic syndrome (HUS). EHEC O104:H4 caused the largest ever recorded EHEC outbreak in Germany in 2011, which in addition showed the so far highest incidence rate of EHEC-related HUS worldwide. The aggressive outbreak strain carries an unusual combination of virulence traits characteristic to both EHEC-a chromosomally integrated Stx-encoding bacteriophage, and enteroaggregative Escherichia coli-pAA plasmid-encoded aggregative adherence fimbriae mediating its tight adhesion to epithelia cells. There are currently still open questions regarding the 2011 EHEC outbreak, e.g., with respect to the exact molecular mechanisms resulting in the hypervirulence of the strain, the natural reservoir of EHEC O104:H4, and suitable therapeutic strategies. Nevertheless, our knowledge on these issues has substantially expanded since 2011. Here, we present an overview of the epidemiological, clinical, microbiological, and molecular biological data available on the 2011 German EHEC O104:H4 outbreak.
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Affiliation(s)
| | - Michael Berger
- Institute of Hygiene, University of Münster, Münster, Germany
| | | | - Helge Karch
- Institute of Hygiene, University of Münster, Münster, Germany
| | - Petya Berger
- Institute of Hygiene, University of Münster, Münster, Germany.
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Microvesicle Involvement in Shiga Toxin-Associated Infection. Toxins (Basel) 2017; 9:toxins9110376. [PMID: 29156596 PMCID: PMC5705991 DOI: 10.3390/toxins9110376] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Revised: 11/15/2017] [Accepted: 11/16/2017] [Indexed: 12/16/2022] Open
Abstract
Shiga toxin is the main virulence factor of enterohemorrhagic Escherichia coli, a non-invasive pathogen that releases virulence factors in the intestine, causing hemorrhagic colitis and, in severe cases, hemolytic uremic syndrome (HUS). HUS manifests with acute renal failure, hemolytic anemia and thrombocytopenia. Shiga toxin induces endothelial cell damage leading to platelet deposition in thrombi within the microvasculature and the development of thrombotic microangiopathy, mostly affecting the kidney. Red blood cells are destroyed in the occlusive capillary lesions. This review focuses on the importance of microvesicles shed from blood cells and their participation in the prothrombotic lesion, in hemolysis and in the transfer of toxin from the circulation into the kidney. Shiga toxin binds to blood cells and may undergo endocytosis and be released within microvesicles. Microvesicles normally contribute to intracellular communication and remove unwanted components from cells. Many microvesicles are prothrombotic as they are tissue factor- and phosphatidylserine-positive. Shiga toxin induces complement-mediated hemolysis and the release of complement-coated red blood cell-derived microvesicles. Toxin was demonstrated within blood cell-derived microvesicles that transported it to renal cells, where microvesicles were taken up and released their contents. Microvesicles are thereby involved in all cardinal aspects of Shiga toxin-associated HUS, thrombosis, hemolysis and renal failure.
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Induction of Shiga Toxin-Encoding Prophage by Abiotic Environmental Stress in Food. Appl Environ Microbiol 2017; 83:AEM.01378-17. [PMID: 28778890 DOI: 10.1128/aem.01378-17] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Accepted: 07/24/2017] [Indexed: 11/20/2022] Open
Abstract
The prophage-encoded Shiga toxin is a major virulence factor in Stx-producing Escherichia coli (STEC). Toxin production and phage production are linked and occur after induction of the RecA-dependent SOS response. However, food-related stress and Stx-prophage induction have not been studied at the single-cell level. This study investigated the effects of abiotic environmental stress on stx expression by single-cell quantification of gene expression in STEC O104:H4 Δstx2::gfp::ampr In addition, the effect of stress on production of phage particles was determined. The lethality of stressors, including heat, HCl, lactic acid, hydrogen peroxide, and high hydrostatic pressure, was selected to reduce cell counts by 1 to 2 log CFU/ml. The integrity of the bacterial membrane after exposure to stress was measured by propidium iodide (PI). The fluorescent signals of green fluorescent protein (GFP) and PI were quantified by flow cytometry. The mechanism of prophage induction by stress was evaluated by relative gene expression of recA and cell morphology. Acid (pH < 3.5) and H2O2 (2.5 mM) induced the expression of stx2 in about 18% and 3% of the population, respectively. The mechanism of prophage induction by acid differs from that of induction by H2O2 H2O2 induction but not acid induction corresponded to production of infectious phage particles, upregulation of recA, and cell filamentation. Pressure (200 MPa) or heat did not induce the Stx2-encoding prophage (Stx2-prophage). Overall, the quantification method developed in this study allowed investigation of prophage induction and physiological properties at the single-cell level. H2O2 and acids mediate different pathways to induce Stx2-prophage.IMPORTANCE Induction of the Stx-prophage in STEC results in production of phage particles and Stx and thus relates to virulence as well as the transduction of virulence genes. This study developed a method for a detection of the induction of Stx-prophages at the single-cell level; membrane permeability and an indication of SOS response to environmental stress were additionally assessed. H2O2 and mitomycin C induced expression of the prophage and activated a SOS response. In contrast, HCl and lactic acid induced the Stx-prophage but not the SOS response. The lifestyle of STEC exposes the organism to intestinal and extraintestinal environments that impose oxidative and acid stress. A more thorough understanding of the influence of food processing-related stressors on Stx-prophage expression thus facilitates control of STEC in food systems by minimizing prophage induction during food production and storage.
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ppGpp and cytotoxicity diversity in Shiga toxin-producing Escherichia coli (STEC) isolates. Epidemiol Infect 2017; 145:2204-2211. [PMID: 28587697 DOI: 10.1017/s0950268817001091] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Shiga toxin-producing Escherichia coli (STEC) is a known food pathogen, which main reservoir is the intestine of ruminants. The abundance of different STEC lineages in nature reflect a heterogeneity that is characterised by the differential expression of certain genotypic characteristics, which in turn are influenced by the environmental conditions to which the microorganism is exposed. Bacterial homeostasis and stress response are under the control of the alarmone guanosine tetraphosphate (ppGpp), which intrinsic levels varies across the E. coli species. In the present study, 50 STEC isolates from healthy sheep were evaluated regarding their ppGpp content, cytotoxicity and other relevant genetic and phenotypic characteristics. We found that the level of ppGpp and cytotoxicity varied considerably among the examined strains. Isolates that harboured the stx2 gene were the least cytotoxic and presented the highest levels of ppGpp. All stx2 isolates belonged to phylogroup A, while strains that carried stx1 or both stx1 and stx2 genes pertained to phylogroup B1. All but two stx2 isolates belonged to the stx2b subtype. Strains that belonged to phylogroup B1 displayed on average low levels of ppGpp and high cytotoxicity. Overall, there was a negative correlation between cytotoxicity and ppGpp.
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Shiga Toxin (Verotoxin)-producing
Escherichia coli and Foodborne Disease:
A Review. Food Saf (Tokyo) 2017; 5:35-53. [PMID: 32231928 DOI: 10.14252/foodsafetyfscj.2016029] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Accepted: 03/31/2017] [Indexed: 12/22/2022] Open
Abstract
Shiga toxin (verotoxin)-producing Escherichia coli (STEC) is an important cause of foodborne disease. Since outcomes of the infections with STEC have a broad range of manifestation from asymptomatic infection or mild intestinal discomfort, to bloody diarrhea, hemolytic uremic syndrome (HUS), end-stage renal disease (ESRD), and death, the disease is a serious burden in public health and classified as a notifiable infectious disease in many countries. Cattle and other ruminants are considered to be the major reservoirs of STEC though isolation of STEC from other animals have been reported. Hence, the source of contamination extends to a wide range of foods, not only beef products but also fresh produce, water, and environment contaminated by excretes from the animals, mainly cattle. A low- infectious dose of STEC makes the disease relatively contagious, and causes outbreaks with unknown contamination sources and, therefore, as a preventive measure against STEC infection, it is important to obtain characteristics of prevailing STEC isolates in the region through robust surveillance. Analysis of the isolates by pulsed-field gel electrophoresis (PFGE) and multiple-locus variable-number tandem repeat analysis (MLVA) could help finding unrecognized foodborne outbreaks due to consumption of respective contaminated sources. However, though the results of molecular analysis of the isolates could indicate linkage of sporadic cases of STEC infection, it is hardly concluded that the cases are related via contaminated food source if it were not for epidemiological information. Therefore, it is essential to combine the results of strain analysis and epidemiological investigation rapidly to detect rapidly foodborne outbreaks caused by bacteria. This article reviews STEC infection as foodborne disease and further discusses key characteristics of STEC including pathogenesis, clinical manifestation, prevention and control of STEC infection. We also present the recent situation of the disease in Japan based on the surveillance of STEC infection.
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Hayes S, Mahony J, Nauta A, van Sinderen D. Metagenomic Approaches to Assess Bacteriophages in Various Environmental Niches. Viruses 2017; 9:v9060127. [PMID: 28538703 PMCID: PMC5490804 DOI: 10.3390/v9060127] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Revised: 05/18/2017] [Accepted: 05/19/2017] [Indexed: 12/15/2022] Open
Abstract
Bacteriophages are ubiquitous and numerous parasites of bacteria and play a critical evolutionary role in virtually every ecosystem, yet our understanding of the extent of the diversity and role of phages remains inadequate for many ecological niches, particularly in cases in which the host is unculturable. During the past 15 years, the emergence of the field of viral metagenomics has drastically enhanced our ability to analyse the so-called viral ‘dark matter’ of the biosphere. Here, we review the evolution of viral metagenomic methodologies, as well as providing an overview of some of the most significant applications and findings in this field of research.
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Affiliation(s)
- Stephen Hayes
- School of Microbiology, University College Cork, Cork T12 YT20, Ireland.
| | - Jennifer Mahony
- School of Microbiology, University College Cork, Cork T12 YT20, Ireland.
- APC Microbiome Institute, University College Cork, Cork T12 YT20, Ireland.
| | - Arjen Nauta
- Friesland Campina, Amersfoort 3800 BN, The Netherlands.
| | - Douwe van Sinderen
- School of Microbiology, University College Cork, Cork T12 YT20, Ireland.
- APC Microbiome Institute, University College Cork, Cork T12 YT20, Ireland.
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64
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OxyR2 Modulates OxyR1 Activity and Vibrio cholerae Oxidative Stress Response. Infect Immun 2017; 85:IAI.00929-16. [PMID: 28138024 DOI: 10.1128/iai.00929-16] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Accepted: 01/25/2017] [Indexed: 12/29/2022] Open
Abstract
Bacteria have developed capacities to deal with different stresses and adapt to different environmental niches. The human pathogen Vibrio cholerae, the causative agent of the severe diarrheal disease cholera, utilizes the transcriptional regulator OxyR to activate genes related to oxidative stress resistance, including peroxiredoxin PrxA, in response to hydrogen peroxide. In this study, we identified another OxyR homolog in V. cholerae, which we named OxyR2, and we renamed the previous OxyR OxyR1. We found that OxyR2 is required to activate its divergently transcribed gene ahpC, encoding an alkylhydroperoxide reductase, independently of H2O2 A conserved cysteine residue in OxyR2 is critical for this function. Mutation of either oxyR2 or ahpC rendered V. cholerae more resistant to H2O2 RNA sequencing analyses indicated that OxyR1-activated oxidative stress-resistant genes were highly expressed in oxyR2 mutants even in the absence of H2O2 Further genetic analyses suggest that OxyR2-activated AhpC modulates OxyR1 activity by maintaining low intracellular concentrations of H2O2 Furthermore, we showed that ΔoxyR2 and ΔahpC mutants were less fit when anaerobically grown bacteria were exposed to low levels of H2O2 or incubated in seawater. These results suggest that OxyR2 and AhpC play important roles in the V. cholerae oxidative stress response.
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65
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Ichimura K, Shimizu T, Matsumoto A, Hirai S, Yokoyama E, Takeuchi H, Yahiro K, Noda M. Nitric oxide-enhanced Shiga toxin production was regulated by Fur and RecA in enterohemorrhagic Escherichia coli O157. Microbiologyopen 2017; 6. [PMID: 28294553 PMCID: PMC5552940 DOI: 10.1002/mbo3.461] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Revised: 01/20/2017] [Accepted: 02/01/2017] [Indexed: 12/27/2022] Open
Abstract
Enterohemorrhagic Escherichia coli (EHEC) produces Shiga toxin 1 (Stx1) and Shiga toxin 2 (Stx2). Nitric oxide (NO), which acts as an antimicrobial defense molecule, was found to enhance the production of Stx1 and Stx2 in EHEC under anaerobic conditions. Although EHEC O157 has two types of anaerobic NO reductase genes, an intact norV and a deleted norV, in the deleted norV‐type EHEC, a high concentration of NO (12–29 μmol/L, maximum steady‐state concentration) is required for enhanced Stx1 production and a low concentration of NO (~12 μmol/L, maximum steady‐state concentration) is sufficient for enhanced Stx2 production under anaerobic conditions. These results suggested that different concentration thresholds of NO elicit a discrete set of Stx1 and Stx2 production pathways. Moreover, the enhancement of Shiga toxin production in the intact norV‐type EHEC required treatment with a higher concentration of NO than was required for enhancement of Shiga toxin production in the deleted norV‐type EHEC, suggesting that the specific NorV type plays an important role in the level of enhancement of Shiga toxin production in response to NO. Finally, Fur derepression and RecA activation in EHEC were shown to participate in the NO‐enhanced Stx1 and Stx2 production, respectively.
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Affiliation(s)
- Kimitoshi Ichimura
- Departments of Molecular Infectiology, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - Takeshi Shimizu
- Departments of Molecular Infectiology, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - Akio Matsumoto
- Pharmacology, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - Shinichiro Hirai
- Division of Bacteriology, Chiba Prefectural Institute of Public Health, Chiba, Japan
| | - Eiji Yokoyama
- Division of Bacteriology, Chiba Prefectural Institute of Public Health, Chiba, Japan
| | - Hiroki Takeuchi
- Departments of Molecular Infectiology, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - Kinnosuke Yahiro
- Departments of Molecular Infectiology, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - Masatoshi Noda
- Departments of Molecular Infectiology, Graduate School of Medicine, Chiba University, Chiba, Japan
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66
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Bondy-Denomy J, Qian J, Westra ER, Buckling A, Guttman DS, Davidson AR, Maxwell KL. Prophages mediate defense against phage infection through diverse mechanisms. THE ISME JOURNAL 2016; 10:2854-2866. [PMID: 27258950 PMCID: PMC5148200 DOI: 10.1038/ismej.2016.79] [Citation(s) in RCA: 256] [Impact Index Per Article: 32.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Revised: 03/31/2016] [Accepted: 04/04/2016] [Indexed: 12/18/2022]
Abstract
The activity of bacteriophages poses a major threat to bacterial survival. Upon infection, a temperate phage can either kill the host cell or be maintained as a prophage. In this state, the bacteria carrying the prophage is at risk of superinfection, where another phage injects its genetic material and competes for host cell resources. To avoid this, many phages have evolved mechanisms that alter the bacteria and make it resistant to phage superinfection. The mechanisms underlying these phentoypic conversions and the fitness consequences for the host are poorly understood, and systematic studies of superinfection exclusion mechanisms are lacking. In this study, we examined a wide range of Pseudomonas aeruginosa phages and found that they mediate superinfection exclusion through a variety of mechanisms, some of which affected the type IV pilus and O-antigen, and others that functioned inside the cell. The strongest resistance mechanism was a surface modification that we showed is cost-free for the bacterial host in a natural soil environment and in a Caenorhabditis. elegans infection model. This study represents the first systematic approach to address how a population of prophages influences phage resistance and bacterial behavior in P. aeruginosa.
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Affiliation(s)
- Joseph Bondy-Denomy
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Jason Qian
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Edze R Westra
- Environment and Sustainability Institute, Biosciences, University of Exeter, Penryn, UK
| | - Angus Buckling
- Environment and Sustainability Institute, Biosciences, University of Exeter, Penryn, UK
| | - David S Guttman
- Centre for the Analysis of Genome Evolution and Function, University of Toronto, Toronto, ON, Canada
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON, Canada
| | - Alan R Davidson
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada
| | - Karen L Maxwell
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, ON, Canada
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67
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Touchon M, Bernheim A, Rocha EP. Genetic and life-history traits associated with the distribution of prophages in bacteria. THE ISME JOURNAL 2016; 10:2744-2754. [PMID: 27015004 PMCID: PMC5113838 DOI: 10.1038/ismej.2016.47] [Citation(s) in RCA: 221] [Impact Index Per Article: 27.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/27/2015] [Revised: 02/17/2016] [Accepted: 02/24/2016] [Indexed: 01/07/2023]
Abstract
Nearly half of the sequenced bacteria are lysogens and many of their prophages encode adaptive traits. Yet, the variables driving prophage distribution remain undetermined. We identified 2246 prophages in complete bacterial genomes to study the genetic and life-history traits associated with lysogeny. While optimal growth temperatures and average cell volumes were not associated with lysogeny, prophages were more frequent in pathogens and in bacteria with small minimal doubling times. Their frequency also increased with genome size, but only for genomes smaller than 6 Mb. The number of spacers in CRISPR-Cas systems and the frequency of type III systems were anticorrelated with prophage frequency, but lysogens were more likely to encode type I and type II systems. The minimal doubling time was the trait most correlated with lysogeny, followed by genome size and pathogenicity. We propose that bacteria with highly variable growth rates often encounter lower opportunity costs for lysogeny relative to lysis. These results contribute to explain the paucity of temperate phages in certain bacterial clades and of bacterial lysogens in certain environments. They suggest that genetic and life-history traits affect the contributions of temperate phages to bacterial genomes.
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Affiliation(s)
- Marie Touchon
- Institut Pasteur, Microbial Evolutionary Genomics, Paris, France
- CNRS, UMR3525, Paris, France
| | - Aude Bernheim
- Institut Pasteur, Microbial Evolutionary Genomics, Paris, France
- CNRS, UMR3525, Paris, France
| | - Eduardo Pc Rocha
- Institut Pasteur, Microbial Evolutionary Genomics, Paris, France
- CNRS, UMR3525, Paris, France
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68
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Wu SY, Park GY, Kim SH, Hulme J, An SSA. Diminazene aceturate: an antibacterial agent for Shiga-toxin-producing Escherichia coli O157:H7. DRUG DESIGN DEVELOPMENT AND THERAPY 2016; 10:3363-3378. [PMID: 27789937 PMCID: PMC5072558 DOI: 10.2147/dddt.s114832] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The aim of this study was to investigate the bacteriostatic and bactericidal effects of diminazene aceturate (DA) against five strains of pathogenic bacteria and two strains of nonpathogenic bacteria. The results showed that 5 μg/mL of DA suppressed the growth of pathogenic Escherichia coli by as much as 77% compared with the controls. Enterohemorrhagic E. coli EDL933 (an E. coli O157:H7 strain) was the most sensitive to DA with a minimum inhibitory concentration of 20 μg/mL. Additional investigations showed that DA induced the highest level of intracellular reactive oxygen species in EDL933. A positive correlation between the reactive oxygen species levels and DA concentration was demonstrated. DA (5 μg/mL) was also a potent uncoupler, inducing a stationary phase collapse (70%–75%) in both strains of E. coli O157:H7. Further investigation showed that the collapse was due to the NaCl:DA ratio in the broth and was potassium ion dependent. A protease screening assay was conducted to elucidate the underlying mechanism. It was found that at neutral pH, the hydrolysis of H-Asp-pNA increased by a factor of 2–3 in the presence of DA, implying that DA causes dysregulation of the proton motive force and a decrease in cellular pH. Finally, a commercial verotoxin test showed that DA did not significantly increase toxin production in EDL933 and was a suitable antibacterial agent for Shiga-toxin-producing E. coli.
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Affiliation(s)
- Si-Ying Wu
- Department of BioNano Technology, Gachon BioNano Research Institute, Gachon University, Seongnam-si
| | - Gil-Yong Park
- Department of BioNano Technology, Gachon BioNano Research Institute, Gachon University, Seongnam-si
| | - So-Hee Kim
- Seoul National University Bundang Hospital, Gyeonggi-do, Republic of Korea
| | - John Hulme
- Department of BioNano Technology, Gachon BioNano Research Institute, Gachon University, Seongnam-si
| | - Seong Soo A An
- Department of BioNano Technology, Gachon BioNano Research Institute, Gachon University, Seongnam-si
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69
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Abstract
Pathogenic bacteria must withstand diverse host environments during infection. Environmental signals, such as pH, temperature, nutrient limitation, etc., not only trigger adaptive responses within bacteria to these specific stress conditions but also direct the expression of virulence genes at an appropriate time and place. An appreciation of stress responses and their regulation is therefore essential for an understanding of bacterial pathogenesis. This review considers specific stresses in the host environment and their relevance to pathogenesis, with a particular focus on the enteric pathogen Salmonella.
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Affiliation(s)
- Ferric C Fang
- Department of Microbiology, University of Washington School of Medicine, Seattle, WA 98195-7735, USA; Department of Laboratory Medicine, University of Washington School of Medicine, Seattle, WA 98195-7735, USA.
| | - Elaine R Frawley
- Department of Laboratory Medicine, University of Washington School of Medicine, Seattle, WA 98195-7735, USA
| | - Timothy Tapscott
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Andrés Vázquez-Torres
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, CO 80045, USA
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70
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Mitarai N, Brown S, Sneppen K. Population Dynamics of Phage and Bacteria in Spatially Structured Habitats Using Phage λ and Escherichia coli. J Bacteriol 2016; 198:1783-93. [PMID: 27068593 PMCID: PMC4886755 DOI: 10.1128/jb.00965-15] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2015] [Accepted: 04/05/2016] [Indexed: 01/21/2023] Open
Abstract
UNLABELLED Bacteria living in physically structured habitats are exposed heterogeneously to both resources and different types of phages. While there have been numerous experimental approaches to examine spatially distributed bacteria exposed to phages, there is little theory to guide the design of these experiments, interpret their results, or expand the inferences drawn to a broader ecological and evolutionary context. Plaque formation provides a window into understanding phage-bacterium interactions in physically structured populations, including surfaces, semisolids, and biofilms. We develop models to address the plaque dynamics for a temperate phage and its virulent mutants. The models are compared with phage λ-Escherichia coli system to quantify their applicability. We found that temperate phages gave an increasing number of gradually smaller colonies as the distance increased from the plaque center. For low-lysogen frequency this resulted in plaques with most of the visible colonies at an intermediate distance between the center and periphery. Using spot inoculation, where phages in excess of bacteria were inoculated in a circular area, we measured the frequency and spatial distribution of lysogens. The spot morphology of cII-negative (cII(-)) and cIII(-) mutants of phage λ displays concentric rings of high-density lysogenic colonies. The simplest of these ring morphologies was reproduced by including multiplicity of infection (MOI) sensitivity in lysis-lysogeny decisions, but its failure to explain the occasional observation of multiple rings in cIII(-) mutant phages highlights unknown features of this phage. Our findings demonstrated advantages of temperate phages over virulent phages in exploiting limited resources in spatially distributed microbial populations. IMPORTANCE Phages are the most abundant organisms on earth, and yet little is known about how phages and bacterial hosts are influencing each other in density and evolution. Phages can be either virulent or temperate, a difference that is highlighted when a spatially structured bacterial population is infected. Phage λ is a temperate phage, with a capacity for dormancy that can be modified by single gene knockouts. The stochastic bias in the lysis-lysogeny decision's probability is reflected in plaque morphologies on bacterial lawns. We present a model for plaque morphology of both virulent and temperate phages, taking into account the underlying survival of bacterial microcolonies. It reproduces known plaque morphologies and speaks to advantages of temperate phages in a spatially structured environment.
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Affiliation(s)
- Namiko Mitarai
- Center for Models of Life, Niels Bohr Institute, University of Copenhagen, Copenhagen, DenmarkPrinceton University
| | - Stanley Brown
- Center for Models of Life, Niels Bohr Institute, University of Copenhagen, Copenhagen, DenmarkPrinceton University
| | - Kim Sneppen
- Center for Models of Life, Niels Bohr Institute, University of Copenhagen, Copenhagen, DenmarkPrinceton University
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71
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Colon MP, Chakraborty D, Pevzner Y, Koudelka GB. Mechanisms that Determine the Differential Stability of Stx⁺ and Stx(-) Lysogens. Toxins (Basel) 2016; 8:96. [PMID: 27043626 PMCID: PMC4848623 DOI: 10.3390/toxins8040096] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Revised: 03/23/2016] [Accepted: 03/25/2016] [Indexed: 01/29/2023] Open
Abstract
Phages 933W, BAA2326, 434, and λ are evolutionarily-related temperate lambdoid phages that infect Escherichia coli. Although these are highly-similar phages, BAA2326 and 933W naturally encode Shiga toxin 2 (Stx+), but phage 434 and λ do not (Stx−). Previous reports suggest that the 933W Stx+ prophage forms less stable lysogens in E. coli than does the Stx− prophages λ, P22, and 434. The higher spontaneous induction frequency of the Stx+ prophage may be correlated with both virulence and dispersion of the Stx2-encoding phage. Here, we examined the hypothesis that lysogen instability is a common feature of Stx+ prophages. We found in both the absence and presence of prophage inducers (DNA damaging agents, salts), the Stx+ prophages induce at higher frequencies than do Stx− prophages. The observed instability of Stx+ prophages does not appear to be the result of any differences in phage development properties between Stx+ and Stx− phages. Our results indicate that differential stability of Stx+ and Stx− prophages results from both RecA-dependent and RecA-independent effects on the intracellular concentration of the respective cI repressors.
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Affiliation(s)
- Michael P Colon
- Department of Biological Sciences, University at Buffalo, Buffalo, NY 14260, USA.
| | | | - Yonatan Pevzner
- Department of Biological Sciences, University at Buffalo, Buffalo, NY 14260, USA.
| | - Gerald B Koudelka
- Department of Biological Sciences, University at Buffalo, Buffalo, NY 14260, USA.
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72
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Imamovic L, Ballesté E, Martínez-Castillo A, García-Aljaro C, Muniesa M. Heterogeneity in phage induction enables the survival of the lysogenic population. Environ Microbiol 2016; 18:957-69. [PMID: 26626855 DOI: 10.1111/1462-2920.13151] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Accepted: 11/24/2015] [Indexed: 11/29/2022]
Abstract
Lysogeny by temperate phages provides novel functions for bacteria and shelter for phages. However, under conditions that activate the phage lytic cycle, the benefit of lysogeny becomes a paradox that poses a threat for bacterial population survival. Using Escherichia coli lysogens for Shiga toxin (Stx) phages as model, we demonstrate how lysogenic bacterial populations circumvent extinction after phage induction. A fraction of cells maintains lysogeny, allowing population survival, whereas the other fraction of cells lyse, increasing Stx production and spreading Stx phages. The uninduced cells were still lysogenic for the Stx phage and equally able to induce phages as the original cells, suggesting heterogeneity of the E. coli lysogenic population. The bacterial population can modulate phage induction under stress conditions by the stress regulator RpoS. Cells overexpressing RpoS reduce Stx phage induction and compete with and survive better than cells with baseline RpoS levels. Our observations suggest that population heterogeneity in phage induction could be widespread among other bacterial genera and we propose this is a mechanism positively selected to prevent the extinction of the lysogenic population that can be modulated by environmental conditions.
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Affiliation(s)
- Lejla Imamovic
- Department of Microbiology, University of Barcelona, Diagonal 643, Annex, Floor 0, E-08028, Barcelona, Spain
| | - Elisenda Ballesté
- Department of Microbiology, University of Barcelona, Diagonal 643, Annex, Floor 0, E-08028, Barcelona, Spain
| | - Alexandre Martínez-Castillo
- Department of Microbiology, University of Barcelona, Diagonal 643, Annex, Floor 0, E-08028, Barcelona, Spain
| | - Cristina García-Aljaro
- Department of Microbiology, University of Barcelona, Diagonal 643, Annex, Floor 0, E-08028, Barcelona, Spain
| | - Maite Muniesa
- Department of Microbiology, University of Barcelona, Diagonal 643, Annex, Floor 0, E-08028, Barcelona, Spain
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73
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Feiner R, Argov T, Rabinovich L, Sigal N, Borovok I, Herskovits AA. A new perspective on lysogeny: prophages as active regulatory switches of bacteria. Nat Rev Microbiol 2016; 13:641-50. [PMID: 26373372 DOI: 10.1038/nrmicro3527] [Citation(s) in RCA: 269] [Impact Index Per Article: 33.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Unlike lytic phages, temperate phages that enter lysogeny maintain a long-term association with their bacterial host. In this context, mutually beneficial interactions can evolve that support efficient reproduction of both phages and bacteria. Temperate phages are integrated into the bacterial chromosome as large DNA insertions that can disrupt gene expression, and they may pose a fitness burden on the cell. However, they have also been shown to benefit their bacterial hosts by providing new functions in a bacterium-phage symbiotic interaction termed lysogenic conversion. In this Opinion article, we discuss another type of bacterium-phage interaction, active lysogeny, in which phages or phage-like elements are integrated into the bacterial chromosome within critical genes or operons and serve as switches that regulate bacterial genes via genome excision.
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Affiliation(s)
- Ron Feiner
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Tel Aviv 69978, Israel
| | - Tal Argov
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Tel Aviv 69978, Israel
| | - Lev Rabinovich
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Tel Aviv 69978, Israel
| | - Nadejda Sigal
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Tel Aviv 69978, Israel
| | - Ilya Borovok
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Tel Aviv 69978, Israel
| | - Anat A Herskovits
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Tel Aviv 69978, Israel
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74
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The Shiga toxin 2 production level in enterohemorrhagic Escherichia coli O157:H7 is correlated with the subtypes of toxin-encoding phage. Sci Rep 2015; 5:16663. [PMID: 26567959 PMCID: PMC4645166 DOI: 10.1038/srep16663] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Accepted: 10/19/2015] [Indexed: 01/21/2023] Open
Abstract
Enterohemorrhagic E. coli (EHEC) causes diarrhea and hemorrhagic colitis with life-threatening complications, such as hemolytic uremic syndrome. Their major virulence factor is Shiga toxin (Stx), which is encoded by bacteriophages. Of the two types of Stx, the production of Stx2, particularly that of Stx2a (a subtype of Stx2), is a major risk factor for severe EHEC infections, but the Stx2 production level is highly variable between strains. Here, we define four major and two minor subtypes of Stx2a-encoding phages according to their replication proteins. The subtypes are correlated with Stx2a titers produced by the host O157 strains, suggesting a critical role of the phage subtype in determining the Stx2a production level. We further show that one of the two subclades in the clade 8, a proposed hyper-virulent lineage of O157, carries the Stx2 phage subtype that confers the highest Stx2 production to the host strain. The presence of this subclade may explain the proposed high virulence potential of clade 8. These results provide novel insights into the variation in virulence among O157 strains and highlight the role of phage variation in determining the production level of the virulence factors that phages encode.
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75
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Type III Secretion-Dependent Sensitivity of Escherichia coli O157 to Specific Ketolides. Antimicrob Agents Chemother 2015; 60:459-70. [PMID: 26525795 PMCID: PMC4704242 DOI: 10.1128/aac.02085-15] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Accepted: 10/27/2015] [Indexed: 01/06/2023] Open
Abstract
A subset of Gram-negative bacterial pathogens uses a type III secretion system (T3SS) to open up a conduit into eukaryotic cells in order to inject effector proteins. These modulate pathways to enhance bacterial colonization. In this study, we screened established bioactive compounds for any that could repress T3SS expression in enterohemorrhagic Escherichia coli (EHEC) O157. The ketolides telithromycin and, subsequently, solithromycin both demonstrated repressive effects on expression of the bacterial T3SS at sub-MICs, leading to significant reductions in bacterial binding and actin-rich pedestal formation on epithelial cells. Preincubation of epithelial cells with solithromycin resulted in significantly less attachment of E. coli O157. Moreover, bacteria expressing the T3SS were more susceptible to solithromycin, and there was significant preferential killing of E. coli O157 bacteria when they were added to epithelial cells that had been preexposed to the ketolide. This killing was dependent on expression of the T3SS. Taken together, this research indicates that the ketolide that has accumulated in epithelial cells may traffic back into the bacteria via the T3SS. Considering that neither ketolide induces the SOS response, nontoxic members of this class of antibiotics, such as solithromycin, should be considered for future testing and trials evaluating their use for treatment of EHEC infections. These antibiotics may also have broader significance for treating infections caused by other pathogenic bacteria, including intracellular bacteria, that express a T3SS.
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76
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Transcriptomic analysis of Shiga-toxigenic bacteriophage carriage reveals a profound regulatory effect on acid resistance in Escherichia coli. Appl Environ Microbiol 2015; 81:8118-25. [PMID: 26386055 PMCID: PMC4651098 DOI: 10.1128/aem.02034-15] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Accepted: 09/12/2015] [Indexed: 12/16/2022] Open
Abstract
Shiga-toxigenic bacteriophages are converting lambdoid phages that impart the ability to produce Shiga toxin to their hosts. Little is known about the function of most of the genes carried by these phages or the impact that lysogeny has on the Escherichia coli host. Here we use next-generation sequencing to compare the transcriptomes of E. coli strains infected with an Stx phage, before and after triggering of the bacterial SOS response that initiates the lytic cycle of the phage. We were able to discriminate between bacteriophage genes expressed in the lysogenic and lytic cycles, and we describe transcriptional changes that occur in the bacterial host as a consequence of Stx phage carriage. Having identified upregulation of the glutamic acid decarboxylase (GAD) operon, confirmed by reverse transcription-quantitative PCR (RT-qPCR), we used phenotypic assays to establish the ability of the Stx prophage to confer a greater acid resistance phenotype on the E. coli host. Known phage regulators were overexpressed in E. coli, and the acid resistance of the recombinant strains was tested. The phage-encoded transcriptional regulator CII was identified as the controller of the acid response in the lysogen. Infection of an E. coli O157 strain, from which integrated Stx prophages were previously removed, showed increased acid resistance following infection with a nontoxigenic phage, ϕ24B. In addition to demonstrating this link between Stx phage carriage and E. coli acid resistance, with its implications for survival postingestion, the data set provides a number of other potential insights into the impact of lambdoid phage carriage on the biology of E. coli.
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77
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Busschaert P, Frans I, Crauwels S, Zhu B, Willems K, Bossier P, Michiels C, Verstrepen K, Lievens B, Rediers H. Comparative genome sequencing to assess the genetic diversity and virulence attributes of 15 Vibrio anguillarum isolates. JOURNAL OF FISH DISEASES 2015; 38:795-807. [PMID: 25073650 DOI: 10.1111/jfd.12290] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2014] [Revised: 06/14/2014] [Accepted: 06/19/2014] [Indexed: 06/03/2023]
Abstract
Vibrio anguillarum is the causative agent of vibriosis, a deadly haemorrhagic septicaemic disease affecting various marine and fresh/brackish water fish, bivalves and crustaceans. However, the diversity and virulence mechanisms of this pathogen are still insufficiently known. In this study, we aimed to increase our understanding of V. anguillarum diversity and virulence through comparative genome analysis of 15 V. anguillarum strains, obtained from different hosts or non-host niches and geographical regions, among which 10 and 5 strains were found to be virulent and avirulent, respectively, against sea bass larvae. First, the 15 draft genomes were annotated and screened for putative virulence factors, including genes encoding iron uptake systems, transport systems and non-ribosomal peptide synthetases. Second, comparative genome analysis was performed, focusing on single nucleotide polymorphisms (SNPs) and small insertions and deletions (InDels). Five V. anguillarum strains showed a remarkably high nucleotide identity. However, these strains comprise both virulent and avirulent strains towards sea bass larvae, suggesting that differences in virulence may be caused by subtle nucleotide variations. Clearly, the draft genome sequence of these 15 strains represents a starting point for further genetic research of this economically important fish pathogen.
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Affiliation(s)
- P Busschaert
- Laboratory for Process Microbial Ecology and Bioinspirational Management, Cluster for Bioengineering Technology (CBeT), Department of Microbial and Molecular Systems (M2S), KU Leuven - Campus De Nayer, Sint-Katelijne-Waver, Belgium
| | - I Frans
- Laboratory for Process Microbial Ecology and Bioinspirational Management, Cluster for Bioengineering Technology (CBeT), Department of Microbial and Molecular Systems (M2S), KU Leuven - Campus De Nayer, Sint-Katelijne-Waver, Belgium
| | - S Crauwels
- Laboratory for Process Microbial Ecology and Bioinspirational Management, Cluster for Bioengineering Technology (CBeT), Department of Microbial and Molecular Systems (M2S), KU Leuven - Campus De Nayer, Sint-Katelijne-Waver, Belgium
| | - B Zhu
- VIB Lab for Systems Biology & Centre of Microbial and Plant Genetics (CMPG), Lab for Genetics and Genomics, M2S, KU Leuven, Leuven, Belgium
| | - K Willems
- Laboratory for Process Microbial Ecology and Bioinspirational Management, Cluster for Bioengineering Technology (CBeT), Department of Microbial and Molecular Systems (M2S), KU Leuven - Campus De Nayer, Sint-Katelijne-Waver, Belgium
| | - P Bossier
- Laboratory of Aquaculture & Artemia Reference Centre, Department of Animal Production, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - C Michiels
- Centre for Food and Microbial Technology, M2S, KU Leuven, Leuven, Belgium
| | - K Verstrepen
- VIB Lab for Systems Biology & Centre of Microbial and Plant Genetics (CMPG), Lab for Genetics and Genomics, M2S, KU Leuven, Leuven, Belgium
| | - B Lievens
- Laboratory for Process Microbial Ecology and Bioinspirational Management, Cluster for Bioengineering Technology (CBeT), Department of Microbial and Molecular Systems (M2S), KU Leuven - Campus De Nayer, Sint-Katelijne-Waver, Belgium
| | - H Rediers
- Laboratory for Process Microbial Ecology and Bioinspirational Management, Cluster for Bioengineering Technology (CBeT), Department of Microbial and Molecular Systems (M2S), KU Leuven - Campus De Nayer, Sint-Katelijne-Waver, Belgium
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78
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Kunsmann L, Rüter C, Bauwens A, Greune L, Glüder M, Kemper B, Fruth A, Wai SN, He X, Lloubes R, Schmidt MA, Dobrindt U, Mellmann A, Karch H, Bielaszewska M. Virulence from vesicles: Novel mechanisms of host cell injury by Escherichia coli O104:H4 outbreak strain. Sci Rep 2015; 5:13252. [PMID: 26283502 PMCID: PMC4539607 DOI: 10.1038/srep13252] [Citation(s) in RCA: 102] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Accepted: 07/22/2015] [Indexed: 12/27/2022] Open
Abstract
The highly virulent Escherichia coli O104:H4 that caused the large 2011 outbreak of diarrhoea and haemolytic uraemic syndrome secretes blended virulence factors of enterohaemorrhagic and enteroaggregative E. coli, but their secretion pathways are unknown. We demonstrate that the outbreak strain releases a cocktail of virulence factors via outer membrane vesicles (OMVs) shed during growth. The OMVs contain Shiga toxin (Stx) 2a, the major virulence factor of the strain, Shigella enterotoxin 1, H4 flagellin, and O104 lipopolysaccharide. The OMVs bind to and are internalised by human intestinal epithelial cells via dynamin-dependent and Stx2a-independent endocytosis, deliver the OMV-associated virulence factors intracellularly and induce caspase-9-mediated apoptosis and interleukin-8 secretion. Stx2a is the key OMV component responsible for the cytotoxicity, whereas flagellin and lipopolysaccharide are the major interleukin-8 inducers. The OMVs represent novel ways for the E. coli O104:H4 outbreak strain to deliver pathogenic cargoes and injure host cells.
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Affiliation(s)
- Lisa Kunsmann
- Institute of Hygiene and the National Consulting Laboratory for Hemolytic Uremic Syndrome, University of Münster, 48149 Münster, Germany
| | - Christian Rüter
- Institute of Infectiology, Center for Molecular Biology of Inflammation (ZMBE), University of Münster, 48149 Münster, Germany
| | - Andreas Bauwens
- Institute of Hygiene and the National Consulting Laboratory for Hemolytic Uremic Syndrome, University of Münster, 48149 Münster, Germany
| | - Lilo Greune
- Institute of Infectiology, Center for Molecular Biology of Inflammation (ZMBE), University of Münster, 48149 Münster, Germany
| | - Malte Glüder
- Institute of Hygiene and the National Consulting Laboratory for Hemolytic Uremic Syndrome, University of Münster, 48149 Münster, Germany
| | - Björn Kemper
- Biomedical Technology Center, University of Muenster, 48149 Münster, Germany
| | - Angelika Fruth
- National Reference Center for Salmonella and Other Enteric Pathogens, Robert Koch Institute, Branch Wernigerode, 38855 Wernigerode, Germany
| | - Sun Nyunt Wai
- Department of Molecular Biology, Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, S-90187 Umeå, Sweden
| | - Xiaohua He
- Western Regional Research Center, Agricultural Research Service, United States Department of Agriculture (USDA), Albany, CA 94710, USA
| | - Roland Lloubes
- Laboratoire d'Ingenierie des Systemes Macromoleculaires UMR7255, CNRS-Aix-Marseille Université, 13402 Marseille cedex 20, France
| | - M Alexander Schmidt
- Institute of Infectiology, Center for Molecular Biology of Inflammation (ZMBE), University of Münster, 48149 Münster, Germany
| | - Ulrich Dobrindt
- Institute of Hygiene and the National Consulting Laboratory for Hemolytic Uremic Syndrome, University of Münster, 48149 Münster, Germany
| | - Alexander Mellmann
- Institute of Hygiene and the National Consulting Laboratory for Hemolytic Uremic Syndrome, University of Münster, 48149 Münster, Germany
| | - Helge Karch
- Institute of Hygiene and the National Consulting Laboratory for Hemolytic Uremic Syndrome, University of Münster, 48149 Münster, Germany
| | - Martina Bielaszewska
- Institute of Hygiene and the National Consulting Laboratory for Hemolytic Uremic Syndrome, University of Münster, 48149 Münster, Germany
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79
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Downing T. Tackling Drug Resistant Infection Outbreaks of Global Pandemic Escherichia coli ST131 Using Evolutionary and Epidemiological Genomics. Microorganisms 2015; 3:236-67. [PMID: 27682088 PMCID: PMC5023239 DOI: 10.3390/microorganisms3020236] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Revised: 04/28/2015] [Accepted: 04/30/2015] [Indexed: 11/16/2022] Open
Abstract
High-throughput molecular screening is required to investigate the origin and diffusion of antimicrobial resistance in pathogen outbreaks. The most frequent cause of human infection is Escherichia coli, which is dominated by sequence type 131 (ST131)-a set of rapidly radiating pandemic clones. The highly infectious clades of ST131 originated firstly by a mutation enhancing conjugation and adhesion. Secondly, single-nucleotide polymorphisms occurred enabling fluoroquinolone-resistance, which is near-fixed in all ST131. Thirdly, broader resistance through beta-lactamases has been gained and lost frequently, symptomatic of conflicting environmental selective effects. This flexible approach to gene exchange is worrying and supports the proposition that ST131 will develop an even wider range of plasmid and chromosomal elements promoting antimicrobial resistance. To stop ST131, deep genome sequencing is required to understand the origin, evolution and spread of antimicrobial resistance genes. Phylogenetic methods that decipher past events can predict future patterns of virulence and transmission based on genetic signatures of adaptation and gene exchange. Both the effect of partial antimicrobial exposure and cell dormancy caused by variation in gene expression may accelerate the development of resistance. High-throughput sequencing can decode measurable evolution of cell populations within patients associated with systems-wide changes in gene expression during treatments. A multi-faceted approach can enhance assessment of antimicrobial resistance in E. coli ST131 by examining transmission dynamics between hosts to achieve a goal of pre-empting resistance before it emerges by optimising antimicrobial treatment protocols.
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Affiliation(s)
- Tim Downing
- School of Biotechnology, Faculty of Science and Health, Dublin City University, Dublin 9, Ireland.
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80
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Hemmatinezhad B, Khamesipour F, Mohammadi M, Safarpoor Dehkordi F, Mashak Z. Microbiological Investigation of O-Serogroups, Virulence Factors and Antimicrobial Resistance Properties of Shiga Toxin-Producing E
scherichia Coli
Isolated from Ostrich, Turkey and Quail Meats. J Food Saf 2015. [DOI: 10.1111/jfs.12199] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- Behsan Hemmatinezhad
- Young Researchers and Elites Club; Shahrekord Branch; Islamic Azad University; Shahrekord Iran
| | - Faham Khamesipour
- Young Researchers and Elites Club; Shahrekord Branch; Islamic Azad University; Shahrekord Iran
| | - Milad Mohammadi
- Faculty of Veterinary Medicine; Shahrekord Branch; Islamic Azad University; Shahrekord Iran
| | | | - Zohreh Mashak
- Department of Food Hygiene; Karaj Branch; Islamic Azad University; Karaj Iran
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81
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Ilyina TS. Filamentous bacteriophages and their role in the virulence and evolution of pathogenic bacteria. MOLECULAR GENETICS MICROBIOLOGY AND VIROLOGY 2015. [DOI: 10.3103/s0891416815010036] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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82
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Iversen H, Lindbäck T, L’Abée-Lund TM, Roos N, Aspholm M, Stenfors Arnesen L. The gut bacterium Bacteroides thetaiotaomicron influences the virulence potential of the enterohemorrhagic Escherichia coli O103:H25. PLoS One 2015; 10:e0118140. [PMID: 25719195 PMCID: PMC4342160 DOI: 10.1371/journal.pone.0118140] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Accepted: 12/17/2014] [Indexed: 11/18/2022] Open
Abstract
Enterohemorrhagic E. coli (EHEC) is associated with severe gastrointestinal disease. Upon entering the gastrointestinal tract, EHEC is exposed to a fluctuating environment and a myriad of other bacterial species. To establish an infection, EHEC strains have to modulate their gene expression according to the GI tract environment. In order to explore the interspecies interactions between EHEC and an human intestinal commensal, the global gene expression profile was determined of EHEC O103:H25 (EHEC NIPH-11060424) co-cultured with B. thetaiotaomicron (CCUG 10774) or grown in the presence of spent medium from B. thetaiotaomicron. Microarray analysis revealed that approximately 1% of the EHEC NIPH-11060424 genes were significantly up-regulated both in co-culture (30 genes) and in the presence of spent medium (44 genes), and that the affected genes differed between the two conditions. In co-culture, genes encoding structural components of the type three secretion system were among the most affected genes with an almost 4-fold up-regulation, while the most affected genes in spent medium were involved in chemotaxis and were more than 3-fold up-regulated. The operons for type three secretion system (TTSS) are located on the Locus of enterocyte effacement (LEE) pathogenicity island, and qPCR showed that genes of all five operons (LEE1-LEE5) were up-regulated. Moreover, an increased adherence to HeLa cells was observed in EHEC NIPH-11060424 exposed to B. thetaiotaomicron. Expression of stx2 genes, encoding the main virulence factor of EHEC, was down-regulated in both conditions (co-culture/spent medium). These results show that expression of EHEC genes involved in colonization and virulence is modulated in response to direct interspecies contact between cells, or to diffusible factors released from B. thetaiotaomicron. Such interspecies interactions could allow the pathogen to recognize its predilection site and modulate its behaviour accordingly, thus increasing the efficiency of colonization of the colon mucosa, facilitating its persistence and increasing its virulence potential.
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Affiliation(s)
- Hildegunn Iversen
- Department of Food Safety and Infection Biology, Norwegian University of Life Sciences, Oslo, Norway
| | - Toril Lindbäck
- Department of Food Safety and Infection Biology, Norwegian University of Life Sciences, Oslo, Norway
| | - Trine M. L’Abée-Lund
- Department of Food Safety and Infection Biology, Norwegian University of Life Sciences, Oslo, Norway
| | - Norbert Roos
- Department of Biosciences, University of Oslo, Oslo, Norway
| | - Marina Aspholm
- Department of Food Safety and Infection Biology, Norwegian University of Life Sciences, Oslo, Norway
| | - Lotte Stenfors Arnesen
- Department of Food Safety and Infection Biology, Norwegian University of Life Sciences, Oslo, Norway
- * E-mail:
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83
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Iversen H, L' Abée-Lund TM, Aspholm M, Arnesen LPS, Lindbäck T. Commensal E. coli Stx2 lysogens produce high levels of phages after spontaneous prophage induction. Front Cell Infect Microbiol 2015; 5:5. [PMID: 25692100 PMCID: PMC4315091 DOI: 10.3389/fcimb.2015.00005] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Accepted: 01/12/2015] [Indexed: 12/22/2022] Open
Abstract
Enterohemorrhagic E. coli (EHEC) is a food-borne pathogen that causes disease ranging from uncomplicated diarrhea to life-threatening hemolytic uremic syndrome (HUS) and nervous system complications. Shiga toxin 2 (Stx2) is the major virulence factor of EHEC and is critical for development of HUS. The genes encoding Stx2 are carried by lambdoid bacteriophages and the toxin production is tightly linked to the production of phages during lytic cycle. It has previously been suggested that commensal E. coli could amplify the production of Stx2-phages and contribute to the severity of disease. In this study we examined the susceptibility of commensal E. coli strains to the Stx2-converting phage ϕ734, isolated from a highly virulent EHEC O103:H25 (NIPH-11060424). Among 38 commensal E. coli strains from healthy children below 5 years, 15 were lysogenized by the ϕ734 phage, whereas lytic infection was not observed. Three of the commensal E. coli ϕ734 lysogens were tested for stability, and appeared stable and retained the phage for at least 10 cultural passages. When induced to enter lytic cycle by H2O2 treatment, 8 out of 13 commensal lysogens produced more ϕ734 phages than NIPH-11060424. Strikingly, five of them even spontaneously (non-induced) produced higher levels of phage than the H2O2 induced NIPH-11060424. An especially high frequency of HUS (60%) was seen among children infected by NIPH-11060424 during the outbreak in 2006. Based on our findings, a high Stx2 production by commensal E. coli lysogens cannot be ruled out as a contributor to the high frequency of HUS during this outbreak.
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Affiliation(s)
- Hildegunn Iversen
- Department of Food Safety and Infection Biology, Norwegian University of Life Sciences Oslo, Norway
| | - Trine M L' Abée-Lund
- Department of Food Safety and Infection Biology, Norwegian University of Life Sciences Oslo, Norway
| | - Marina Aspholm
- Department of Food Safety and Infection Biology, Norwegian University of Life Sciences Oslo, Norway
| | - Lotte P S Arnesen
- Department of Food Safety and Infection Biology, Norwegian University of Life Sciences Oslo, Norway
| | - Toril Lindbäck
- Department of Food Safety and Infection Biology, Norwegian University of Life Sciences Oslo, Norway
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84
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Touchon M, Bobay LM, Rocha EPC. The chromosomal accommodation and domestication of mobile genetic elements. Curr Opin Microbiol 2014; 22:22-9. [DOI: 10.1016/j.mib.2014.09.010] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Accepted: 09/17/2014] [Indexed: 11/17/2022]
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85
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Impact of spontaneous prophage induction on the fitness of bacterial populations and host-microbe interactions. J Bacteriol 2014; 197:410-9. [PMID: 25404701 DOI: 10.1128/jb.02230-14] [Citation(s) in RCA: 170] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Bacteriophages and genetic elements, such as prophage-like elements, pathogenicity islands, and phage morons, make up a considerable amount of bacterial genomes. Their transfer and subsequent activity within the host's genetic circuitry have had a significant impact on bacterial evolution. In this review, we consider what underlying mechanisms might cause the spontaneous activity of lysogenic phages in single bacterial cells and how the spontaneous induction of prophages can lead to competitive advantages for and influence the lifestyle of bacterial populations or the virulence of pathogenic strains.
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86
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Abstract
Bacteriophage genomes found in a range of bacterial pathogens encode a diverse array of virulence factors ranging from superantigens or pore forming lysins to numerous exotoxins. Recent studies have uncovered an entirely new class of bacterial virulence factors, called effector proteins or effector toxins, which are encoded within phage genomes that reside among several pathovars of Escherichia coli and Salmonella enterica. These effector proteins have multiple domains resulting in proteins that can be multifunctional. The effector proteins encoded within phage genomes are translocated directly from the bacterial cytosol into their eukaryotic target cells by specialized bacterial type three secretion systems (T3SSs). In this review, we will give an overview of the different types of effector proteins encoded within phage genomes and examine their roles in bacterial pathogenesis.
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Affiliation(s)
- E Fidelma Boyd
- Department of Biological Sciences; University of Delaware; Newark, DE USA
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87
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Bloch S, Nejman-Faleńczyk B, Dydecka A, Łoś JM, Felczykowska A, Węgrzyn A, Węgrzyn G. Different expression patterns of genes from the exo-xis region of bacteriophage λ and Shiga toxin-converting bacteriophage Ф24B following infection or prophage induction in Escherichia coli. PLoS One 2014; 9:e108233. [PMID: 25310402 PMCID: PMC4195576 DOI: 10.1371/journal.pone.0108233] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Accepted: 08/28/2014] [Indexed: 11/19/2022] Open
Abstract
Lambdoid bacteriophages serve as useful models in microbiological and molecular studies on basic biological process. Moreover, this family of viruses plays an important role in pathogenesis of enterohemorrhagic Escherichia coli (EHEC) strains, as they are carriers of genes coding for Shiga toxins. Efficient expression of these genes requires lambdoid prophage induction and multiplication of the phage genome. Therefore, understanding the mechanisms regulating these processes appears essential for both basic knowledge and potential anti-EHEC applications. The exo-xis region, present in genomes of lambdoid bacteriophages, contains highly conserved genes of largely unknown functions. Recent report indicated that the Ea8.5 protein, encoded in this region, contains a newly discovered fused homeodomain/zinc-finger fold, suggesting its plausible regulatory role. Moreover, subsequent studies demonstrated that overexpression of the exo-xis region from a multicopy plasmid resulted in impaired lysogenization of E. coli and more effective induction of λ and Ф24B prophages. In this report, we demonstrate that after prophage induction, the increase in phage DNA content in the host cells is more efficient in E. coli bearing additional copies of the exo-xis region, while survival rate of such bacteria is lower, which corroborated previous observations. Importantly, by using quantitative real-time reverse transcription PCR, we have determined patterns of expressions of particular genes from this region. Unexpectedly, in both phages λ and Ф24B, these patterns were significantly different not only between conditions of the host cells infection by bacteriophages and prophage induction, but also between induction of prophages with various agents (mitomycin C and hydrogen peroxide). This may shed a new light on our understanding of regulation of lambdoid phage development, depending on the mode of lytic cycle initiation.
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Affiliation(s)
- Sylwia Bloch
- Department of Molecular Biology, University of Gdańsk, Gdańsk, Poland
| | | | | | - Joanna M. Łoś
- Department of Molecular Biology, University of Gdańsk, Gdańsk, Poland
| | | | - Alicja Węgrzyn
- Department of Microbiology, University of Szczecin, Szczecin, Poland
| | - Grzegorz Węgrzyn
- Department of Molecular Biology, University of Gdańsk, Gdańsk, Poland
- * E-mail:
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88
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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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89
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Abstract
Integrated phages (prophages) are major contributors to the diversity of bacterial gene repertoires. Domestication of their components is thought to have endowed bacteria with molecular systems involved in secretion, defense, warfare, and gene transfer. However, the rates and mechanisms of domestication remain unknown. We used comparative genomics to study the evolution of prophages within the bacterial genome. We identified over 300 vertically inherited prophages within enterobacterial genomes. Some of these elements are very old and might predate the split between Escherichia coli and Salmonella enterica. The size distribution of prophage elements is bimodal, suggestive of rapid prophage inactivation followed by much slower genetic degradation. Accordingly, we observed a pervasive pattern of systematic counterselection of nonsynonymous mutations in prophage genes. Importantly, such patterns of purifying selection are observed not only on accessory regions but also in core phage genes, such as those encoding structural and lysis components. This suggests that bacterial hosts select for phage-associated functions. Several of these conserved prophages have gene repertoires compatible with described functions of adaptive prophage-derived elements such as bacteriocins, killer particles, gene transfer agents, or satellite prophages. We suggest that bacteria frequently domesticate their prophages. Most such domesticated elements end up deleted from the bacterial genome because they are replaced by analogous functions carried by new prophages. This puts the bacterial genome in a state of continuous flux of acquisition and loss of phage-derived adaptive genes.
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90
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RS1 satellite phage promotes diversity of toxigenic Vibrio cholerae by driving CTX prophage loss and elimination of lysogenic immunity. Infect Immun 2014; 82:3636-43. [PMID: 24935981 DOI: 10.1128/iai.01699-14] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In El Tor biotype strains of toxigenic Vibrio cholerae, the CTXϕ prophage often resides adjacent to a chromosomally integrated satellite phage genome, RS1, which produces RS1ϕ particles by using CTX prophage-encoded morphogenesis proteins. RS1 encodes RstC, an antirepressor against the CTXϕ repressor RstR, which cooperates with the host-encoded LexA protein to maintain CTXϕ lysogeny. We found that superinfection of toxigenic El Tor strains with RS1ϕ, followed by inoculation of the transductants into the adult rabbit intestine, caused elimination of the resident CTX prophage-producing nontoxigenic derivatives at a high frequency. Further studies using recA deletion mutants and a cloned rstC gene showed that the excision event was recA dependent and that introduction of additional copies of the cloned rstC gene instead of infection with RS1ϕ was sufficient to enhance CTXϕ elimination. Our data suggest that once it is excised from the chromosome, the elimination of CTX prophage from host cells is driven by the inability to reestablish CTXϕ lysogeny while RstC is overexpressed. However, with eventual loss of the additional copies of rstC, the nontoxigenic derivatives can act as precursors of new toxigenic strains by acquiring the CTX prophage either through reinfection with CTXϕ or by chitin-induced transformation. These results provide new insights into the role of RS1ϕ in V. cholerae evolution and the emergence of highly pathogenic clones, such as the variant strains associated with recent devastating epidemics of cholera in Asia, sub-Saharan Africa, and Haiti.
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91
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Abstract
ABSTRACT
To help assess the clinical and public health risks associated with different Shiga toxin-producing
Escherichia coli
(STEC) strains, an empirical classification scheme was used to classify STEC into five “seropathotypes” (seropathotype A [high risk] to seropathotypes D and E [minimal risk]). This definition is of considerable value in cases of human infection but is also problematic because not all STEC infections are fully characterized and coupled to reliable clinical information. Outbreaks with emerging hybrid strains continuously challenge our understanding of virulence potential and may result in incorrect classification of specific pathotypes; an example is the hybrid strain that caused the 2011 outbreak in Germany, STEC/EAggEC O104:H4, which may deserve an alternative seropathotype designation. The integration of mobile virulence factors in the stepwise and parallel evolution of pathogenic lineages of STEC collides with the requirements of a good taxonomy, which separates elements of each group into subgroups that are mutually exclusive, unambiguous, and, together, include all possibilities. The concept of (sero)-pathotypes is therefore challenged, and the need to identify factors of STEC that absolutely predict the potential to cause human disease is obvious. Because the definition of hemolytic-uremic syndrome (HUS) is distinct, a basic and primary definition of HUS-associated
E. coli
(HUSEC) for first-line public health action is proposed:
stx2
in a background of an
eae-
or
aggR
-positive
E. coli
followed by a second-line subtyping of
stx
genes that refines the definition of HUSEC to include only
stx2a
and
stx2d
. All other STEC strains are considered “low-risk” STEC.
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92
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Chekabab SM, Jubelin G, Dozois CM, Harel J. PhoB activates Escherichia coli O157:H7 virulence factors in response to inorganic phosphate limitation. PLoS One 2014; 9:e94285. [PMID: 24710330 PMCID: PMC3978041 DOI: 10.1371/journal.pone.0094285] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2013] [Accepted: 03/13/2014] [Indexed: 01/15/2023] Open
Abstract
Enterohemorrhagic Escherichia coli (EHEC), an emerging food- and water-borne hazard, is highly pathogenic to humans. In the environment, EHEC must survive phosphate (Pi) limitation. The response to such Pi starvation is an induction of the Pho regulon including the Pst system that senses Pi variation. The interplay between the virulence of EHEC, Pho-Pst system and environmental Pi remains unknown. To understand the effects of Pi deprivation on the molecular mechanisms involved in EHEC survival and virulence under Pho regulon control, we undertook transcriptome profiling of the EDL933 wild-type strain grown under high Pi and low Pi conditions and its isogenic ΔphoB mutant grown in low Pi conditions. The differentially expressed genes included 1067 Pi-dependent genes and 603 PhoB-dependent genes. Of these 131 genes were both Pi and PhoB-dependent. Differentially expressed genes that were selected included those involved in Pi homeostasis, cellular metabolism, acid stress, oxidative stress and RpoS-dependent stress responses. Differentially expressed virulence systems included the locus of enterocyte effacement (LEE) encoding the type-3 secretion system (T3SS) and its effectors, as well as BP-933W prophage encoded Shiga toxin 2 genes. Moreover, PhoB directly regulated LEE and stx2 gene expression through binding to specific Pho boxes. However, in Pi-rich medium, constitutive activation of the Pho regulon decreased LEE gene expression and reduced adherence to HeLa cells. Together, these findings reveal that EHEC has evolved a sophisticated response to Pi limitation involving multiple biochemical strategies that contribute to its ability to respond to variations in environmental Pi and to coordinating the virulence response.
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Affiliation(s)
- Samuel Mohammed Chekabab
- Research Group on Infectious Diseases of Swine, Montreal University, Faculty of Veterinary Medicine, Saint-Hyacinthe, Québec, Canada
| | - Grégory Jubelin
- Unité de Microbiologie (UR454) INRA Clermont-Ferrand-Theix, St-Genes-Champanelle, France
| | | | - Josée Harel
- Research Group on Infectious Diseases of Swine, Montreal University, Faculty of Veterinary Medicine, Saint-Hyacinthe, Québec, Canada
- * E-mail:
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93
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Insights into the diversity of φRSM phages infecting strains of the phytopathogen Ralstonia solanacearum complex: regulation and evolution. Mol Genet Genomics 2014; 289:589-98. [PMID: 24619102 DOI: 10.1007/s00438-014-0835-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Accepted: 02/21/2014] [Indexed: 12/28/2022]
Abstract
The filamentous φRSM phages (φRSM1 and φRSM3) have integration/excision capabilities in the phytopathogenic bacterium Ralstonia solanacearum. In the present study, we further investigated φRSM-like sequences present in the genomes of R. solanacearum strains belonging to the four major evolutionary lineages (phylotypes I-IV). Based on bioinformatics and comparative genomic analyses, we found that φRSM homologs are highly diverse in R. solanacearum complex strains. We detected an open reading frame (ORF)15 located upstream of the gene for φRSM integrase, which exhibited amino acid sequence similarity to phage repressor proteins. ORF15-encoded protein (a putative repressor) was found to encode a 104-residue polypeptide containing a DNA-binding (helix-turn-helix) domain and was expressed in R. solanacearum lysogenic strains. This suggested that φRSM3-ORF15 might be involved in the establishment and maintenance of a lysogenic state, as well as in phage immunity. Comparison of the putative repressor proteins and their binding sites within φRSM-related prophages provides insights into how these regulatory systems of filamentous phages have evolved and diverged in the R. solanacearum complex. In conclusion, φRSM phages represent a unique group of filamentous phages that are equipped with innate integration/excision (ORF14) and regulatory systems (ORF15).
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94
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Negative feedback and transcriptional overshooting in a regulatory network for horizontal gene transfer. PLoS Genet 2014; 10:e1004171. [PMID: 24586200 PMCID: PMC3937220 DOI: 10.1371/journal.pgen.1004171] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Accepted: 12/26/2013] [Indexed: 11/23/2022] Open
Abstract
Horizontal gene transfer (HGT) is a major force driving bacterial evolution. Because of their ability to cross inter-species barriers, bacterial plasmids are essential agents for HGT. This ability, however, poses specific requisites on plasmid physiology, in particular the need to overcome a multilevel selection process with opposing demands. We analyzed the transcriptional network of plasmid R388, one of the most promiscuous plasmids in Proteobacteria. Transcriptional analysis by fluorescence expression profiling and quantitative PCR revealed a regulatory network controlled by six transcriptional repressors. The regulatory network relied on strong promoters, which were tightly repressed in negative feedback loops. Computational simulations and theoretical analysis indicated that this architecture would show a transcriptional burst after plasmid conjugation, linking the magnitude of the feedback gain with the intensity of the transcriptional burst. Experimental analysis showed that transcriptional overshooting occurred when the plasmid invaded a new population of susceptible cells. We propose that transcriptional overshooting allows genome rebooting after horizontal gene transfer, and might have an adaptive role in overcoming the opposing demands of multilevel selection. In the environment, bacteria often evolve by the acquisition of new genes from different species. Plasmids are small DNA molecules that mediate horizontal gene transfer in bacteria, thus they are fundamental agents for the spread of antibiotic resistances. Plasmids replicate inside the bacterial cytoplasm, and propagate infectiously by contact. Plasmids control these two ways of multiplication, but like many other symbionts they suffer from a tradeoff. If plasmids become very infective, they can spread fast and successfully, but this damages the bacterial hosts they depend upon. If, on the contrary, plasmids become very mild, the host is able to grow better but the ability of plasmids to infect new hosts is hampered. We have studied the regulatory mechanisms plasmids use to overcome this paradox. We discovered that negative feedback, a regulatory motif ubiquitous in the plasmid network, allows transient activation of plasmid functions immediately after plasmids invade a new host. This might be an adaptive strategy for plasmids to be highly infective without damaging their hosts, and it illustrates a natural mechanism for DNA transplantation that could be implemented in synthetic genomic transplants.
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95
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Phenethyl isothiocyanate inhibits shiga toxin production in enterohemorrhagic Escherichia coli by stringent response induction. Antimicrob Agents Chemother 2014; 58:2304-15. [PMID: 24492371 DOI: 10.1128/aac.02515-13] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The pathogenicity of enterohemorrhagic Escherichia coli (EHEC) depends on production of Shiga toxins, which are encoded by stx genes located in the genomes of lambdoid prophages. Efficient expression of these genes requires prophage induction and lytic development of phages. Treatment of EHEC infections is problematic due to not only the resistance of various strains to antibiotics but also the fact that many antibiotics cause prophage induction, thus resulting in high-level expression of stx genes. Here we report that E. coli growth, Shiga toxin-converting phage development, and production of the toxin by EHEC are strongly inhibited by phenethyl isothiocyanate (PEITC). We demonstrate that PEITC induces the stringent response in E. coli that is mediated by massive production of a global regulator, guanosine tetraphosphate (ppGpp). The stringent response induction arises most probably from interactions of PEITC with amino acids and from amino acid deprivation-mediated activation of ppGpp synthesis. In mutants unable to synthesize ppGpp, development of Shiga toxin-converting phages and production of Shiga toxin are significantly enhanced. Therefore, ppGpp, which appears at high levels in bacterial cells after stimulation of its production by PEITC, is a negative regulator of EHEC virulence and at the same time efficiently inhibits bacterial growth. This is in contrast to stimulation of virulence of different bacteria by this nucleotide reported previously by others.
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96
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Abstract
While Shiga toxins (Stx) are key determinants of enterohemorrhagic Escherichia coli (EHEC) pathophysiology in humans, their dissemination to target organs following gastrointestinal EHEC infection is still poorly understood. Most types of Stx target cells with globotriaosylceramide (Gb3) receptors, which are expressed on endothelial cells. According to current theory, Stx is trafficked on the surface of peripheral blood cells, and transfer of toxin from these trafficking cells to endothelial cells results in microvascular damage to target organs, including the kidneys and brain. Inside the cell, Stx inhibits protein synthesis, resulting in cell death. Host “repair” responses can lead to microthrombus formation, erythrocyte damage, and reduced oxygen supply, potentially resulting in organ failure. A recent study [L. V. Bentancor et al., mBio 4(5):e00501-13, 2013, doi:10.1128/mBio.00501-13] indicates that another mechanism for Stx “dissemination” needs to be considered. Bentancor et al. demonstrated that high-pressure injection of a plasmid encoding the “prokaryotic” Stx2 sequence into mice can lead to mortality, with pathology indicative of Stx activity and antibody responses to Stx. While the plasmid levels and injection methodology were extreme, the study indicates that these sequences are potentially taken up into eukaryotic cells, transcribed, and translated, producing active Stx. Stx genes are present on integrated bacteriophage genomes in EHEC, and Stx-encoding phages are released following bacterial lysis in the gastrointestinal tract. We therefore need to consider whether bacteriophage sequences can be expressed in eukaryotic cells, what the wider implications are for our understanding of many “bacterial” diseases, and the possibility of developing novel interventions that target bacteriophages.
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97
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Kreuzer KN. DNA damage responses in prokaryotes: regulating gene expression, modulating growth patterns, and manipulating replication forks. Cold Spring Harb Perspect Biol 2013; 5:a012674. [PMID: 24097899 DOI: 10.1101/cshperspect.a012674] [Citation(s) in RCA: 140] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Recent advances in the area of bacterial DNA damage responses are reviewed here. The SOS pathway is still the major paradigm of bacterial DNA damage response, and recent studies have clarified the mechanisms of SOS induction and key physiological roles of SOS including a very major role in genetic exchange and variation. When considering diverse bacteria, it is clear that SOS is not a uniform pathway with one purpose, but rather a platform that has evolved for differing functions in different bacteria. Relating in part to the SOS response, the field has uncovered multiple apparent cell-cycle checkpoints that assist cell survival after DNA damage and remarkable pathways that induce programmed cell death in bacteria. Bacterial DNA damage responses are also much broader than SOS, and several important examples of LexA-independent regulation will be reviewed. Finally, some recent advances that relate to the replication and repair of damaged DNA will be summarized.
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Affiliation(s)
- Kenneth N Kreuzer
- Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710
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98
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Role of filamentous phage SW1 in regulating the lateral flagella of Shewanella piezotolerans strain WP3 at low temperatures. Appl Environ Microbiol 2013; 79:7101-9. [PMID: 24038680 DOI: 10.1128/aem.01675-13] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Low-temperature ecosystems represent the largest biosphere on Earth, and yet our understanding of the roles of bacteriophages in these systems is limited. Here, the influence of the cold-active filamentous phage SW1 on the phenotype and gene transcription of its host, Shewanella piezotolerans WP3 (WP3), was investigated by construction of a phage-free strain (WP3ΔSW1), which was compared with the wild-type strain. The expression of 49 genes, including 16 lateral flagellar genes, was found to be significantly influenced by SW1 at 4°C, as demonstrated by comparative whole-genome microarray analysis. WP3ΔSW1 was shown to have a higher production of lateral flagella than WP3 and enhanced swarming motility when cultivated on solid agar plates. Besides, SW1 has a remarkable impact on the expression of a variety of host genes in liquid culture, particularly the genes related to the membrane and to the production of lateral flagella. These results suggest that the deep-sea bacterium WP3 might balance the high-energy demands of phage maintenance and swarming motility at low temperatures. The phage SW1 is shown to have a significant influence on the swarming ability of the host and thus may play an important role in adjusting the fitness of the cells in the deep-sea environment.
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99
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ppGpp-dependent negative control of DNA replication of Shiga toxin-converting bacteriophages in Escherichia coli. J Bacteriol 2013; 195:5007-15. [PMID: 23995636 DOI: 10.1128/jb.00592-13] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The pathogenicity of enterohemorrhagic Escherichia coli (EHEC) strains depends on the production of Shiga toxins that are encoded on lambdoid prophages. Effective production of these toxins requires prophage induction and subsequent phage replication. Previous reports indicated that lytic development of Shiga toxin-converting bacteriophages is inhibited in amino acid-starved bacteria. However, those studies demonstrated that inhibition of both phage-derived plasmid replication and production of progeny virions occurred during the stringent as well as the relaxed response to amino acid starvation, i.e., in the presence as well as the absence of high levels of ppGpp, an alarmone of the stringent response. Therefore, we asked whether ppGpp influences DNA replication and lytic development of Shiga toxin-converting bacteriophages. Lytic development of 5 such bacteriophages was tested in an E. coli wild-type strain and an isogenic mutant that does not produce ppGpp (ppGpp(0)). In the absence of ppGpp, production of progeny phages was significantly (in the range of an order of magnitude) more efficient than in wild-type cells. Such effects were observed in infected bacteria as well as after prophage induction. All tested bacteriophages formed considerably larger plaques on lawns formed by ppGpp(0) bacteria than on those formed by wild-type E. coli. The efficiency of synthesis of phage DNA and relative amount of lambdoid plasmid DNA were increased in cells devoid of ppGpp relative to bacteria containing a basal level of this nucleotide. We conclude that ppGpp negatively influences the lytic development of Shiga toxin-converting bacteriophages and that phage DNA replication efficiency is limited by the stringent control alarmone.
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100
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Genes from the exo-xis region of λ and Shiga toxin-converting bacteriophages influence lysogenization and prophage induction. Arch Microbiol 2013; 195:693-703. [PMID: 23979561 PMCID: PMC3824215 DOI: 10.1007/s00203-013-0920-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2013] [Revised: 07/31/2013] [Accepted: 08/09/2013] [Indexed: 01/17/2023]
Abstract
The exo–xis region, present in genomes of lambdoid bacteriophages, contains highly conserved genes of largely unknown functions. In this report, using bacteriophage λ and Shiga toxin-converting bacteriophage ϕ24Β, we demonstrate that the presence of this region on a multicopy plasmid results in impaired lysogenization of Escherichia coli and delayed, while more effective, induction of prophages following stimulation by various agents (mitomycin C, hydrogen peroxide, UV irradiation). Spontaneous induction of λ and ϕ24Β prophages was also more efficient in bacteria carrying additional copies of the corresponding exo–xis region on plasmids. No significant effects of an increased copy number of genes located between exo and xis on both efficiency of adsorption on the host cells and lytic development inside the host cell of these bacteriophages were found. We conclude that genes from the exo–xis region of lambdoid bacteriophages participate in the regulation of lysogenization and prophage maintenance.
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