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Neudek K, Kunz T, Barth H, Schmidt H. Excess A-subunits of Shiga toxin 2a are produced in enterohemorrhagic Escherichia coli. Sci Rep 2025; 15:16712. [PMID: 40368985 PMCID: PMC12078605 DOI: 10.1038/s41598-025-01342-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2024] [Accepted: 05/06/2025] [Indexed: 05/16/2025] Open
Abstract
Shiga toxins (Stx) produced by Shiga toxin-producing Escherichia coli (STEC) and enterohemorrhagic E. coli (EHEC) are ribosome-inactivating AB5 proteins that consist of one enzymatic active A-subunit (StxA) and a pentamer of non-covalently linked B-subunits (StxB). The description of Stx as an AB5 protein and the observation that A-subunits without their corresponding B-subunits also intoxicate eukaryotic cells, led to the question whether A- and B-subunits are produced in the bacteria in a 1:5 ratio or whether the A-subunit of the clinically most prominent subtype Stx2a is transcribed in excess revealing free A-subunits released in the bacterial environment. The aim of this study was therefore, to investigate the genetic and protein-based background for this observation in six Stx2a-encoding STEC and EHEC wildtype strains. For this purpose, transcriptional analysis of the Stx2a subunit genes, stxA2a and stxB2a, was performed by quantitative real-time PCR in one foodborne O113:H21 STEC isolate (strain TS18/08) and five HUS-associated EHEC strains with the serotypes O157:H7/H- (HUSEC003, HUSEC004), O103:H- (HUSEC008), O26:H11 (HUSEC018), and O104:H4 (LB226692). Contrary to the hypothesis that the A- and B-subunit genes are expressed in a ratio of 1:5 comparable to the holotoxin structure or in a ratio of 1:1 based on the operon structure, the results showed that stxA2a was expressed 1.90 ± 0.55-times stronger than the gene encoding the B-subunit, possibly indicating the presence of free A-subunits. In addition, strain-specific differences regarding the mRNA fold-changes of the A-subunit gene were observed. By use of native polyacrylamide gel electrophoresis and subsequent Western blot analysis, those single A-subunits were indeed detected in the culture supernatants of all six strains. To investigate whether the transcription ratios between A- and B-subunits observed are in a similar range as the amount of subunit proteins present after translation, a quantitative ELISA specific for StxA2a and StxB2a was established. Quantification of the subunits on protein level by use of ELISA revealed that the subunit ratio of StxA2a:StxB2a is 1.10 ± 0.20 for the strains HUSEC003, HUSEC004 and HUSEC008, but 4.63 ± 0.31 for the strains TS18/08, LB226692, and HUSEC018. The results of this study demonstrated that on both, the transcriptional and the translational level, the established 1:5 subunit ratio is not present in all investigated strains. In addition, the ratios observed after translation indicate that in some strains StxA2a subunits are even produced in higher amounts than B-subunits.
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Affiliation(s)
- Katrin Neudek
- Department of Food Microbiology and Hygiene, Institute of Food Science and Biotechnology, University of Hohenheim, Garbenstrasse 28, 70599, Stuttgart, Germany
| | - Theresa Kunz
- Department of Food Microbiology and Hygiene, Institute of Food Science and Biotechnology, University of Hohenheim, Garbenstrasse 28, 70599, Stuttgart, Germany
| | - Holger Barth
- Institute of Experimental and Clinical Pharmacology, Toxicology and Pharmacology of Natural Products, University of Ulm Medical Center, Albert-Einstein-Allee 11, 89081, Ulm, Germany
| | - Herbert Schmidt
- Department of Food Microbiology and Hygiene, Institute of Food Science and Biotechnology, University of Hohenheim, Garbenstrasse 28, 70599, Stuttgart, Germany.
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2
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Banerjee R. Tiny but Mighty: Small RNAs-The Micromanagers of Bacterial Survival, Virulence, and Host-Pathogen Interactions. Noncoding RNA 2025; 11:36. [PMID: 40407594 PMCID: PMC12101431 DOI: 10.3390/ncrna11030036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2025] [Revised: 04/07/2025] [Accepted: 04/28/2025] [Indexed: 05/26/2025] Open
Abstract
Bacterial pathogens have evolved diverse strategies to infect hosts, evade immune responses, and establish successful infections. While the role of transcription factors in bacterial virulence is well documented, emerging evidence highlights the significant contribution of small regulatory RNAs (sRNAs) in bacterial pathogenesis. These sRNAs function as posttranscriptional regulators that fine-tune gene expression, enabling bacteria to adapt rapidly to challenging environments. This review explores the multifaceted roles of bacterial sRNAs in host-pathogen interactions. Firstly, it examines how sRNAs regulate pathogenicity by modulating the expression of key virulence factors, including fimbriae, toxins, and secretion systems, followed by discussing the role of sRNAs in bacterial stress response mechanisms that counteract host immune defenses, such as oxidative and envelope stress. Additionally, this review investigates the involvement of sRNAs in antibiotic resistance by regulating efflux pumps, biofilm formation, and membrane modifications, which contribute to multi-drug resistance phenotypes. Lastly, this review highlights how sRNAs contribute to intra- and interspecies communication through quorum sensing, thereby coordinating bacterial behavior in response to environmental cues. Understanding these regulatory networks governed by sRNAs is essential for the development of innovative antimicrobial strategies. This review highlights the growing significance of sRNAs in bacterial pathogenicity and explores their potential as therapeutic targets for the treatment of bacterial infections.
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Affiliation(s)
- Rajdeep Banerjee
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
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3
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Sun H, Huang D, Pang Y, Chen J, Kang C, Zhao M, Yang B. Key roles of two-component systems in intestinal signal sensing and virulence regulation in enterohemorrhagic Escherichia coli. FEMS Microbiol Rev 2024; 48:fuae028. [PMID: 39537200 PMCID: PMC11644481 DOI: 10.1093/femsre/fuae028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2024] [Revised: 11/10/2024] [Accepted: 11/12/2024] [Indexed: 11/16/2024] Open
Abstract
Enterohemorrhagic Escherichia coli (EHEC) is a foodborne pathogen that infects humans by colonizing the large intestine. Upon reaching the large intestine, EHEC mediates local signal recognition and the transcriptional regulation of virulence genes to promote adherence and colonization in a highly site-specific manner. Two-component systems (TCSs) represent an important strategy used by EHEC to couple external stimuli with the regulation of gene expression, thereby allowing EHEC to rapidly adapt to changing environmental conditions. An increasing number of studies published in recent years have shown that EHEC senses a variety of host- and microbiota-derived signals present in the human intestinal tract and coordinates the expression of virulence genes via multiple TCS-mediated signal transduction pathways to initiate the disease-causing process. Here, we summarize how EHEC detects a wide range of intestinal signals and precisely regulates virulence gene expression through multiple signal transduction pathways during the initial stages of infection, with a particular emphasis on the key roles of TCSs. This review provides valuable insights into the importance of TCSs in EHEC pathogenesis, which has relevant implications for the development of antibacterial therapies against EHEC infection.
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Affiliation(s)
- Hongmin Sun
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin 300457, China
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin 300457, China
| | - Di Huang
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin 300457, China
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin 300457, China
| | - Yu Pang
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin 300457, China
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin 300457, China
| | - Jingnan Chen
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin 300457, China
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin 300457, China
| | - Chenbo Kang
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin 300457, China
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin 300457, China
| | - Mengjie Zhao
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin 300457, China
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin 300457, China
| | - Bin Yang
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin 300457, China
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin 300457, China
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4
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Bucher MJ, Czyż DM. Phage against the Machine: The SIE-ence of Superinfection Exclusion. Viruses 2024; 16:1348. [PMID: 39339825 PMCID: PMC11436027 DOI: 10.3390/v16091348] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2024] [Revised: 08/10/2024] [Accepted: 08/20/2024] [Indexed: 09/30/2024] Open
Abstract
Prophages can alter their bacterial hosts to prevent other phages from infecting the same cell, a mechanism known as superinfection exclusion (SIE). Such alterations are facilitated by phage interactions with critical bacterial components involved in motility, adhesion, biofilm production, conjugation, antimicrobial resistance, and immune evasion. Therefore, the impact of SIE extends beyond the immediate defense against superinfection, influencing the overall fitness and virulence of the bacteria. Evaluating the interactions between phages and their bacterial targets is critical for leading phage therapy candidates like Pseudomonas aeruginosa, a Gram-negative bacterium responsible for persistent and antibiotic-resistant opportunistic infections. However, comprehensive literature on the mechanisms underlying SIE remains scarce. Here, we provide a compilation of well-characterized and potential mechanisms employed by Pseudomonas phages to establish SIE. We hypothesize that the fitness costs imposed by SIE affect bacterial virulence, highlighting the potential role of this mechanism in the management of bacterial infections.
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Affiliation(s)
- Michael J Bucher
- Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611, USA
| | - Daniel M Czyż
- Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611, USA
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5
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Nakamura K, Taniguchi I, Gotoh Y, Isobe J, Kimata K, Igawa Y, Kitahashi T, Takahashi Y, Nomoto R, Iwabuchi K, Morimoto Y, Iyoda S, Hayashi T. Diversity of Shiga toxin transducing phages in Escherichia coli O145:H28 and the different Shiga toxin 2 production levels associated with short- or long-tailed phages. Front Microbiol 2024; 15:1453887. [PMID: 39165568 PMCID: PMC11333237 DOI: 10.3389/fmicb.2024.1453887] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2024] [Accepted: 07/25/2024] [Indexed: 08/22/2024] Open
Abstract
Shiga toxin (Stx)-producing Escherichia coli (STEC) causes serious gastrointestinal illness, including hemorrhagic colitis and hemolytic uremic syndrome. Two types of Stxs (Stx1 and Stx2) are known and both are encoded by bacteriophages (Stx phages), but the production of Stx2 is known to be a major risk factor for severe STEC infections. The production of Stx2, but not Stx1, is tightly coupled with the induction of Stx phages, and Stx2 production levels vary between STEC strains even within the same serotype. Here, we analyzed the genomic diversity of all Stx phages in 71 strains representing the entire O145:H28 lineage, one of the often highly pathogenic STECs, and the relationship between the variations in Stx phage genomes and the levels of Stx2 production by host strains. Our analysis reveals highly dynamic natures of Stx phages in O145:H28, including the independent acquisition of similar Stx phages by different sublineages, the recent transfer of Stx phage between different sublineages, and the frequent gain and loss of Stx phages in some sublineages. We also show the association of the Stx2 phage types with the Stx2 production levels of host strains: strains carrying short-tailed Stx2 phages exhibited significantly higher Stx2 production levels than those carrying long-tailed Stx2 phages. Detailed analyses of the Stx2 phage genomes revealed that both of short- and long-tailed phages exhibited sequence diversification and they were divided into two groups, respectively, based on the sequence similarity of the phage early region encoding genes responsible for phage induction, short-tailed phages contained early regions clearly different in genetic organization from those in long-tailed phages. Therefore, the variations in the early regions between short-and long-tailed Stx2 phages appeared to be linked to a striking difference in Stx2 production levels in their host strains. These results broaden our understanding of the diversification and dynamism of Stx phages in O145:H28 and the association of Stx2 phage types with the Stx2 production level in this STEC lineage.
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Affiliation(s)
- Keiji Nakamura
- Department of Bacteriology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Itsuki Taniguchi
- Department of Bacteriology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Yasuhiro Gotoh
- Department of Bacteriology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | | | | | - Yukiko Igawa
- Nagano Prefecture Suwa Public Health and Welfare Office, Suwa, Japan
| | | | | | | | - Kaori Iwabuchi
- Iwate Prefectural Research Institute for Environmental Sciences and Public Health, Morioka, Japan
| | - Yo Morimoto
- Hokkaido Institute of Public Health, Sapporo, Japan
| | - Sunao Iyoda
- National Institute of Infectious Diseases, Tokyo, Japan
| | - Tetsuya Hayashi
- Department of Bacteriology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
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6
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Bloch S, Nejman-Faleńczyk B, Licznerska K, Dydecka A, Topka-Bielecka G, Necel A, Węgrzyn A, Węgrzyn G. Complex effects of the exo-xis region of the Shiga toxin-converting bacteriophage Φ24 B genome on the phage development and the Escherichia coli host physiology. J Appl Genet 2024; 65:191-211. [PMID: 37968427 PMCID: PMC10789677 DOI: 10.1007/s13353-023-00799-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2023] [Revised: 10/22/2023] [Accepted: 10/23/2023] [Indexed: 11/17/2023]
Abstract
Lambdoid bacteriophages are excellent models in studies on molecular aspects of virus-host interactions. However, some of them carry genes encoding toxins which are responsible for virulence of pathogenic strains of bacteria. Shiga toxin-converting bacteriophages (Stx phages) encode Shiga toxins that cause virulence of enterohemorrhagic Escherichia coli (EHEC), and their effective production depends on Stx prophage induction. The exo-xis region of the lambdoid phage genome consists of genes which are dispensable for the phage multiplication under laboratory conditions; however, they might modulate the virus development. Nevertheless, their exact effects on the phage and host physiology remained unclear. Here, we present results of complex studies on the role of the exo-xis region of bacteriophage Φ24B, one of Stx2b phages. Transcriptomic analyses, together with proteomic and metabolomic studies, provided the basis for understanding the functions of the exo-xis region. Genes from this region promoted lytic development of the phage over lysogenization. Moreover, expression of the host genes coding for DnaK, DnaJ, GrpE, and GroELS chaperones was impaired in the cells infected with the Δexo-xis phage mutant, relative to the wild-type virus, corroborating the conclusion about lytic development promotion by the exo-xis region. Proteomic and metabolomic analyses indicated also modulation of gad and nrf operons, and levels of amino acids and acylcarnitines, respectively. In conclusion, the exo-xis region controls phage propagation and host metabolism by influencing expression of different phage and bacterial genes, directing the virus to the lytic rather than lysogenic developmental mode.
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Affiliation(s)
- Sylwia Bloch
- Department of Molecular Biology, Faculty of Biology, University of Gdansk, Gdansk, Poland
| | | | | | | | | | - Agnieszka Necel
- Department of Medical Microbiology, Faculty of Medicine, Medical University of Gdansk, Gdansk, Poland
| | - Alicja Węgrzyn
- Phage Therapy Center, University Center for Applied and Interdisciplinary Research, University of Gdansk, Gdansk, Poland
| | - Grzegorz Węgrzyn
- Department of Molecular Biology, Faculty of Biology, University of Gdansk, Gdansk, Poland.
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7
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Pascal SB, Lorenzo R, Farías MVN, Rossen JW, Lucchesi PMA, Krüger A. Characterization of the flanking region of the Shiga toxin operon in Stx2a bacteriophages reveals a diversity of the NanS-p sialate O-acetylesterase gene. AIMS Microbiol 2023; 9:570-590. [PMID: 37649799 PMCID: PMC10462455 DOI: 10.3934/microbiol.2023030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Revised: 07/18/2023] [Accepted: 07/20/2023] [Indexed: 09/01/2023] Open
Abstract
Shiga toxin-producing E. coli (STEC) are diarrheagenic strains that can cause bloody diarrhea and hemolytic-uremic syndrome. Their main virulence factor, the Shiga toxin (Stx), is encoded by phages integrated into the bacterial chromosome. Stx phages are widely diverse and carry many genes with limited or unknown function. As the toxin subtype Stx2a is associated with highly pathogenic strains, this study was mainly focused on the characterization of the stx flanking region of Stx2a phages. Of particular interest was a sialate O-acetylesterase (NanS-p), which has been described previously to be encoded downstream stx in some phage genomes and may confer a growth advantage for STEC. Complete DNA sequences of Stx2a phages and prophages were retrieved from the GenBank database, and the genomic regions from anti-terminator Q to holin S genes were bioinformatically analyzed. Predicted NanSp sequences from phages encoding other Stx subtypes were also studied. Additionally, expression of nanS-p was quantified by qPCR in strains selected from our laboratory collection. The analysis of Stx2a phage genomes showed that all carried the Q, stx2a, nanS-p and S genes, but with allele diversity and other sequence differences. In particular, sequence differences were detected in each of the three domains of NanS-p esterases encoded by Stx2a phages and other Stx phages; however, nanS-p was not identified in the Stx2e, Stx2f and Stx2g phages analyzed. The expression of nanS-p increased in most stx2a-positive strains under phage inducing conditions, as was previously shown for stx2a. As the present work showed diversity at the Q-S region among Stx phages, and particularly in the encoded NanS-p enzyme, future studies will be necessary to evaluate if NanS-p variants differ in their activity and to assess the impact of the absence of nanS-p in certain Stx phages.
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Affiliation(s)
- Stefanía B. Pascal
- Universidad Nacional del Centro de la Provincia de Buenos Aires (UNCPBA), Facultad de Ciencias Veterinarias, CISAPA, Tandil, Buenos Aires, Argentina
- Centro de Investigación Veterinaria de Tandil (CIVETAN), UNCPBA-CICPBA-CONICET, Tandil, Buenos Aires, Argentina
| | - Ramiro Lorenzo
- Centro de Investigación Veterinaria de Tandil (CIVETAN), UNCPBA-CICPBA-CONICET, Tandil, Buenos Aires, Argentina
- Laboratory of Neurophysiology, ULB Neuroscience Institute, Université Libre de Bruxelles (ULB), Brussels, Belgium
| | - María Victoria Nieto Farías
- Universidad Nacional del Centro de la Provincia de Buenos Aires (UNCPBA), Facultad de Ciencias Veterinarias, CISAPA, Tandil, Buenos Aires, Argentina
- Centro de Investigación Veterinaria de Tandil (CIVETAN), UNCPBA-CICPBA-CONICET, Tandil, Buenos Aires, Argentina
| | - John W.A. Rossen
- Laboratory of Medical Microbiology and Infectious Diseases, Isala Hospital, Zwolle, The Netherlands
- Department of Medical Microbiology and Infection Prevention, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Paula M. A. Lucchesi
- Universidad Nacional del Centro de la Provincia de Buenos Aires (UNCPBA), Facultad de Ciencias Veterinarias, CISAPA, Tandil, Buenos Aires, Argentina
- Centro de Investigación Veterinaria de Tandil (CIVETAN), UNCPBA-CICPBA-CONICET, Tandil, Buenos Aires, Argentina
| | - Alejandra Krüger
- Universidad Nacional del Centro de la Provincia de Buenos Aires (UNCPBA), Facultad de Ciencias Veterinarias, CISAPA, Tandil, Buenos Aires, Argentina
- Centro de Investigación Veterinaria de Tandil (CIVETAN), UNCPBA-CICPBA-CONICET, Tandil, Buenos Aires, Argentina
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8
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Yano B, Taniguchi I, Gotoh Y, Hayashi T, Nakamura K. Dynamic changes in Shiga toxin (Stx) 1 transducing phage throughout the evolution of O26:H11 Stx-producing Escherichia coli. Sci Rep 2023; 13:4935. [PMID: 36973327 PMCID: PMC10042803 DOI: 10.1038/s41598-023-32111-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Accepted: 03/21/2023] [Indexed: 03/29/2023] Open
Abstract
Shiga toxin (Stx) is the key virulence factor of Stx-producing Escherichia coli (STEC). All known Stxs (Stx1 and Stx2) are encoded by bacteriophages (Stx phages). Although the genetic diversity of Stx phages has frequently been described, systematic analyses of Stx phages in a single STEC lineage are limited. In this study, focusing on the O26:H11 STEC sequence type 21 (ST21) lineage, where the stx1a gene is highly conserved, we analysed the Stx1a phages in 39 strains representative of the entire ST21 lineage and found a high level of variation in Stx1a phage genomes caused by various mechanisms, including replacement by a different Stx1a phage at the same or different locus. The evolutionary timescale of events changing Stx1a phages in ST21 was also determined. Furthermore, by using an Stx1 quantification system developed in this study, we found notable variations in the efficiency of Stx1 production upon prophage induction, which sharply contrasted with the conserved iron regulated Stx1 production. These variations were associated with the Stx1a phage alteration in some cases but not in other cases; thus, Stx1 production in this STEC lineage was determined by differences not only in Stx1 phages but also in host-encoded factors.
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Affiliation(s)
- Bungo Yano
- Department of Bacteriology, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 815-8582, Japan
| | - Itsuki Taniguchi
- Department of Bacteriology, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 815-8582, Japan
| | - Yasuhiro Gotoh
- Department of Bacteriology, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 815-8582, Japan
| | - Tetsuya Hayashi
- Department of Bacteriology, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 815-8582, Japan
| | - Keiji Nakamura
- Department of Bacteriology, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 815-8582, Japan.
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Miliwebsky E, Jure MÁ, Farfan MJ, Palermo MS. Interactions of Pathogenic Escherichia coli with Gut Microbiota. TRENDING TOPICS IN ESCHERICHIA COLI RESEARCH 2023:277-294. [DOI: 10.1007/978-3-031-29882-0_12] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2025]
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10
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Gelalcha BD, Brown SM, Crocker HE, Agga GE, Kerro Dego O. Regulation Mechanisms of Virulence Genes in Enterohemorrhagic Escherichia coli. Foodborne Pathog Dis 2022; 19:598-612. [PMID: 35921067 DOI: 10.1089/fpd.2021.0103] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Enterohemorrhagic Escherichia coli (EHEC) is one of the most common E. coli pathotypes reported to cause several outbreaks of foodborne illnesses. EHEC is a zoonotic pathogen, and ruminants, especially cattle, are considered important reservoirs for the most common EHEC serotype, E. coli O157:H7. Humans are infected indirectly through the consumption of food (milk, meat, leafy vegetables, and fruits) and water contaminated by animal feces or direct contact with carrier animals or humans. E. coli O157:H7 is one of the most frequently reported causes of foodborne illnesses in developed countries. It employs two essential virulence mechanisms to trigger damage to the host. These are the development of attaching and effacing (AE) phenotypes on the intestinal mucosa of the host and the production of Shiga toxin (Stx) that causes hemorrhagic colitis and hemolytic uremic syndrome. The AE phenotype is controlled by the pathogenicity island, the locus of enterocyte effacement (LEE). The induction of both AE and Stx is under strict and highly complex regulatory mechanisms. Thus, a good understanding of these mechanisms, major proteins expressed, and environmental cues involved in the regulation of the expression of the virulence genes is vital to finding a method to control the colonization of reservoir hosts, especially cattle, and disease development in humans. This review is a concise account of the current state of knowledge of virulence gene regulation in the LEE-positive EHEC.
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Affiliation(s)
- Benti D Gelalcha
- Department of Animal Science, The University of Tennessee Institute of Agriculture, Knoxville, Tennessee, USA
| | - Selina M Brown
- Department of Animal Science, The University of Tennessee Institute of Agriculture, Knoxville, Tennessee, USA
| | - Hannah E Crocker
- Department of Animal Science, The University of Tennessee Institute of Agriculture, Knoxville, Tennessee, USA
| | - Getahun E Agga
- Food Animal Environmental Systems Research Unit, Agricultural Research Service, United States Department of Agriculture, Bowling Green, Kentucky, USA
| | - Oudessa Kerro Dego
- Department of Animal Science, The University of Tennessee Institute of Agriculture, Knoxville, Tennessee, USA
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11
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Abstract
PURPOSE OF REVIEW This review updates recent findings about Escherichia coli O157:H7 virulence factors and its bovine reservoir. This Shiga toxin (Stx)-producing E. coli belongs to the Enterohemorrhagic E. coli (EHEC) pathotype causing hemorrhagic colitis. Its low infectious dose makes it an efficient, severe, foodborne pathogen. Although EHEC remains in the intestine, Stx can translocate systemically and is cytotoxic to microvascular endothelial cells, especially in the kidney and brain. Disease can progress to life-threatening hemolytic uremic syndrome (HUS) with hemolytic anemia, acute kidney failure, and thrombocytopenia. Young children, the immunocompromised, and the elderly are at the highest risk for HUS. Healthy ruminants are the major reservoir of EHEC and cattle are the primary source of human exposure. RECENT FINDINGS Advances in understanding E. coli O157:H7 pathogenesis include molecular mechanisms of virulence, bacterial adherence, type three secretion effectors, intestinal microbiome, inflammation, and reservoir maintenance. SUMMARY Many aspects of E. coli O157:H7 disease remain unclear and include the role of the human and bovine intestinal microbiomes in infection. Therapeutic strategies involve controlling inflammatory responses and/or intestinal barrier function. Finally, elimination/reduction of E. coli O157:H7 in cattle using CRISPR-engineered conjugative bacterial plasmids and/or on-farm management likely hold solutions to reduce infections and increase food safety/security.
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12
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The Chronic Wound Phageome: Phage Diversity and Associations with Wounds and Healing Outcomes. Microbiol Spectr 2022; 10:e0277721. [PMID: 35435739 PMCID: PMC9248897 DOI: 10.1128/spectrum.02777-21] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Two leading impediments to chronic wound healing are polymicrobial infection and biofilm formation. Recent studies have characterized the bacterial fraction of these microbiomes and have begun to elucidate compositional correlations to healing outcomes. However, the factors that drive compositional shifts are still being uncovered. The virome may play an important role in shaping bacterial community structure and function. Previous work on the skin virome determined that it was dominated by bacteriophages, viruses that infect bacteria. To characterize the virome, we enrolled 20 chronic wound patients presenting at an outpatient wound care clinic in a microbiome survey, collecting swab samples from healthy skin and chronic wounds (diabetic, venous, arterial, or pressure) before and after a single, sharp debridement procedure. We investigated the virome using a virus-like particle enrichment procedure, shotgun metagenomic sequencing, and a k-mer-based, reference-dependent taxonomic classification method. Taxonomic composition, diversity, and associations with covariates are presented. We find that the wound virome is highly diverse, with many phages targeting known pathogens, and may influence bacterial community composition and functionality in ways that impact healing outcomes. IMPORTANCE Chronic wounds are an increasing medical burden. These wounds are known to be rich in microbial content, including both bacteria and bacterial viruses (phages). The viruses may play an important role in shaping bacterial community structure and function. We analyzed the virome and bacterial composition of 20 patients with chronic wounds. The viruses found in wounds are highly diverse compared to normal skin, unlike the bacterial composition, where diversity is decreased. These data represent an initial look at this relatively understudied component of the chronic wound microbiome and may help inform future phage-based interventions.
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Intestinal Enteroid Monolayers Model the Human Intestinal Environment for Escherichia coli Infection. J Bacteriol 2022; 204:e0062021. [PMID: 35389257 DOI: 10.1128/jb.00620-21] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Enterohemorrhagic Escherichia coli O157:H7 is an enteric pathogen responsible for bloody diarrhea, hemolytic uremic syndrome, and in severe cases, even death. The study of O157:H7 is difficult due to the high specificity of the bacteria for the human intestine, along with our lack of sufficiently complex human cell culture models. The recent development of human intestinal enteroids derived from intestinal crypt multipotent stem cells has allowed us to construct two-dimensional differentiated epithelial monolayers grown in transwells that mimic the human intestine. Unlike previous studies, saline was added to the apical surface, while maintaining culture media in the basolateral well. The monolayers continued to grow and differentiate with apical saline. Apical infection with O157:H7 or commensal E. coli resulted in robust bacterial growth from 105 to over 108 over 24 h. Despite this robust bacterial growth, commensal E. coli neither adhered to nor damaged the epithelial barrier over 30 h. However, O157:H7 was almost fully adhered (>90%) by 18 h with epithelial damage observed by 30 h. O157:H7 contains the locus of enterocyte effacement (LEE) pathogenicity island responsible for attachment and damage to the intestinal epithelium. Previous studies report the ability of nutrients such as biotin, d-serine, and L-fucose to downregulate LEE gene expression. O157:H7 treated with biotin or L-fucose, but not d-serine displayed both decreased attachment and reduced epithelial damage over 36 h. These data illustrate enteroid monolayers can serve as a suitable model for the study of O157:H7 pathogenesis, and identification of potential therapeutics. IMPORTANCE O157:H7 is difficult to study due to its high specificity for the human intestine and the lack of sufficiently complex human cell culture models. The recent development of human intestinal enteroids derived from intestinal crypt multipotent stem cells has allowed us to construct two-dimensional differentiated epithelial monolayers grown in transwells that mimic the human intestine. Our data illustrates enteroid monolayers can serve as a suitable model for the study of O157:H7 pathogenesis, and allow for identification of potential therapeutics.
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Miura S, Satoh R, Tamamura-Andoh Y, Tokugawa K, Beppu M, Nozaki C, Murata R, Kusumoto M, Uchida I. Intra-macrophage expression of ArtAB toxin gene in Salmonella. MICROBIOLOGY (READING, ENGLAND) 2022; 168. [PMID: 35333707 DOI: 10.1099/mic.0.001152] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Salmonella enterica subspecies enterica serovar Typhimurium (S. Typhimurium) definitive phage type 104 (DT104), S. Worthington, and S. bongori produce ArtAB toxin, which catalyses ADP-ribosylation of pertussis toxin-sensitive G protein. ArtAB gene (artAB) is encoded on a prophage in Salmonella, and prophage induction by SOS-inducing agents is associated with increases in ArtAB production in vitro. However, little is known about the expression of artAB in vivo. Here, we showed a significant increase in artAB transcription of DT104 within macrophage-like RAW264.7 cells. Intracellular expression of ArtAB was also observed by immunofluorescence staining. The induced expression of artAB in DT104 and S. bongori was enhanced by treatment of RAW264.7 cells with phorbol 12-myristate 13-acetate (PMA), which stimulates the production of reactive oxygen species (ROS); however, such induction was not observed in S. Worthington. Upregulation of oxyR, a major regulator of oxidative stress, and cI, a repressor of prophage induction, was observed in S. Worthington within RAW264.7 cells treated with PMA but not in the DT104 strain. Although the expression of oxyR was increased, artAB was upregulated in S. bongori, which lacks the cI gene in the incomplete artAB-encoded prophage. Taken together, oxidative stress plays a role in the production of artAB toxins in macrophages, and high expression levels of oxyR and cI are responsible for the low expression of artAB. Therefore, strain variation in the level of artAB expression within macrophages could be explained by differences in the oxidative stress response of bacteria and might be reflected in its virulence.
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Affiliation(s)
- Shou Miura
- Veterinary Bacteriology, Department of Pathobiology, School of Veterinary Medicine, Rakuno Gakuen University, 582, Bunkyodai-Midorimachi, Ebetsu, Hokkaido, 069-8501, Japan
| | - Rin Satoh
- Veterinary Bacteriology, Department of Pathobiology, School of Veterinary Medicine, Rakuno Gakuen University, 582, Bunkyodai-Midorimachi, Ebetsu, Hokkaido, 069-8501, Japan
| | - Yukino Tamamura-Andoh
- Division of Bacterial and Parasitic Disease, National Institute of Animal Health, Tsukuba, Ibaraki, 305-0856, Japan
| | - Kanetaka Tokugawa
- Veterinary Bacteriology, Department of Pathobiology, School of Veterinary Medicine, Rakuno Gakuen University, 582, Bunkyodai-Midorimachi, Ebetsu, Hokkaido, 069-8501, Japan
| | - Miho Beppu
- Veterinary Bacteriology, Department of Pathobiology, School of Veterinary Medicine, Rakuno Gakuen University, 582, Bunkyodai-Midorimachi, Ebetsu, Hokkaido, 069-8501, Japan
| | - Chiharu Nozaki
- Veterinary Bacteriology, Department of Pathobiology, School of Veterinary Medicine, Rakuno Gakuen University, 582, Bunkyodai-Midorimachi, Ebetsu, Hokkaido, 069-8501, Japan
| | - Ryo Murata
- Veterinary Bacteriology, Department of Pathobiology, School of Veterinary Medicine, Rakuno Gakuen University, 582, Bunkyodai-Midorimachi, Ebetsu, Hokkaido, 069-8501, Japan
| | - Masahiro Kusumoto
- Division of Bacterial and Parasitic Disease, National Institute of Animal Health, Tsukuba, Ibaraki, 305-0856, Japan
| | - Ikuo Uchida
- Veterinary Bacteriology, Department of Pathobiology, School of Veterinary Medicine, Rakuno Gakuen University, 582, Bunkyodai-Midorimachi, Ebetsu, Hokkaido, 069-8501, Japan
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Mcc1229, an Stx2a-amplifying microcin, is produced in vivo and requires CirA for activity. Infect Immun 2021; 90:e0058721. [PMID: 34871041 PMCID: PMC8853679 DOI: 10.1128/iai.00587-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Enterohemorrhagic Escherichia coli (EHEC) strains, including the foodborne pathogen E. coli O157:H7, are responsible for thousands of hospitalizations each year. Various environmental triggers can modulate pathogenicity in EHEC by inducing the expression of Shiga toxin (Stx), which is encoded on a lambdoid prophage and transcribed together with phage late genes. Cell-free supernatants of the sequence type 73 (ST73) E. coli strain 0.1229 are potent inducers of Stx2a production in EHEC, suggesting that 0.1229 secretes a factor that activates the SOS response and leads to phage lysis. We previously demonstrated that this factor, designated microcin 1229 (Mcc1229), was proteinaceous and plasmid-encoded. To further characterize Mcc1229 and support its classification as a microcin, we investigated its regulation, determined its receptor, and identified loci providing immunity. The production of Mcc1229 was increased upon iron limitation, as determined by an enzyme-linked immunosorbent assay (ELISA), lacZ fusions, and quantitative real-time PCR (qRT-PCR). Spontaneous Mcc1229-resistant mutants and targeted gene deletion revealed that CirA was the Mcc1229 receptor. TonB, which interacts with CirA in the periplasm, was also essential for Mcc1229 import. Subcloning of the Mcc1229 plasmid indicated that Mcc activity was neutralized by two open reading frames (ORFs), each predicted to encode a domain of unknown function (DUF)-containing protein. In a germfree mouse model of infection, colonization with 0.1229 suppressed subsequent colonization by EHEC. Although Mcc1229 was produced in vivo, it was dispensable for colonization suppression. The regulation, import, and immunity determinants identified here are consistent with features of other Mccs, suggesting that Mcc1229 should be included in this class of small molecules.
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Lodato PB. The effect of two ribonucleases on the production of Shiga toxin and stx-bearing bacteriophages in Enterohaemorrhagic Escherichia coli. Sci Rep 2021; 11:18372. [PMID: 34526533 PMCID: PMC8443680 DOI: 10.1038/s41598-021-97736-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Accepted: 08/27/2021] [Indexed: 11/20/2022] Open
Abstract
Enterohaemorrhagic Escherichia coli (EHEC) comprise a group of intestinal pathogens responsible for a range of illnesses, including kidney failure and neurological compromise. EHEC produce critical virulence factors, Shiga toxin (Stx) 1 or 2, and the synthesis of Stx2 is associated with worse disease manifestations. Infected patients only receive supportive treatment because some conventional antibiotics enable toxin production. Shiga toxin 2 genes (stx2) are carried in λ-like bacteriophages (stx2-phages) inserted into the EHEC genome as prophages. Factors that cause DNA damage induce the lytic cycle of stx2-phages, leading to Stx2 production. The phage Q protein is critical for transcription antitermination of stx2 and phage lytic genes. This study reports that deficiency of two endoribonucleases (RNases), E and G, significantly delayed cell lysis and impaired production of both Stx2 and stx2-phages, unlike deficiency of either enzyme alone. Moreover, scarcity of both enzymes reduced the concentrations of Q and stx2 transcripts and slowed cell growth.
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Affiliation(s)
- Patricia B Lodato
- Department of Microbiology and Immunology, Kirksville College of Osteopathic Medicine, A.T. Still University, Kirksville, MO, 63501, USA.
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Ismail MH, Michie KA, Goh YF, Noorian P, Kjelleberg S, Duggin IG, McDougald D, Rice SA. The Repressor C Protein, Pf4r, Controls Superinfection of Pseudomonas aeruginosa PAO1 by the Pf4 Filamentous Phage and Regulates Host Gene Expression. Viruses 2021; 13:1614. [PMID: 34452479 PMCID: PMC8402870 DOI: 10.3390/v13081614] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Revised: 08/09/2021] [Accepted: 08/13/2021] [Indexed: 12/17/2022] Open
Abstract
It has been shown that the filamentous phage, Pf4, plays an important role in biofilm development, stress tolerance, genetic variant formation and virulence in Pseudomonas aeruginosa PAO1. These behaviours are linked to the appearance of superinfective phage variants. Here, we have investigated the molecular mechanism of superinfection as well as how the Pf4 phage can control host gene expression to modulate host behaviours. Pf4 exists as a prophage in PAO1 and encodes a homologue of the P2 phage repressor C and was recently named Pf4r. Through a combination of molecular techniques, ChIPseq and transcriptomic analyses, we show a critical site in repressor C (Pf4r) where a mutation in the site, 788799A>G (Ser4Pro), causes Pf4r to lose its function as the immunity factor against reinfection by Pf4. X-ray crystal structure analysis shows that Pf4r forms symmetric homo-dimers homologous to the E.coli bacteriophage P2 RepC protein. A mutation, Pf4r*, associated with the superinfective Pf4r variant, found at the dimer interface, suggests dimer formation may be disrupted, which derepresses phage replication. This is supported by multi-angle light scattering (MALS) analysis, where the Pf4r* protein only forms monomers. The loss of dimerisation also explains the loss of Pf4r's immunity function. Phenotypic assays showed that Pf4r increased LasB activity and was also associated with a slight increase in the percentage of morphotypic variants. ChIPseq and transcriptomic analyses suggest that Pf4r also likely functions as a transcriptional regulator for other host genes. Collectively, these data suggest the mechanism by which filamentous phages play such an important role in P. aeruginosa biofilm development.
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Affiliation(s)
- Muhammad Hafiz Ismail
- Singapore Centre for Environmental Life Sciences Engineering, Singapore 637551, Singapore; (M.H.I.); (Y.F.G.); (S.K.); (D.M.)
- The School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore
| | - Katharine A. Michie
- Structural Biology Facility, Mark Wainwright Analytical Centre, The University of New South Wales, Sydney, NSW 2052, Australia;
| | - Yu Fen Goh
- Singapore Centre for Environmental Life Sciences Engineering, Singapore 637551, Singapore; (M.H.I.); (Y.F.G.); (S.K.); (D.M.)
| | - Parisa Noorian
- The iThree Institute, The University of Technology Sydney, Sydney, NSW 2007, Australia; (P.N.); (I.G.D.)
| | - Staffan Kjelleberg
- Singapore Centre for Environmental Life Sciences Engineering, Singapore 637551, Singapore; (M.H.I.); (Y.F.G.); (S.K.); (D.M.)
- The School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore
| | - Iain G. Duggin
- The iThree Institute, The University of Technology Sydney, Sydney, NSW 2007, Australia; (P.N.); (I.G.D.)
| | - Diane McDougald
- Singapore Centre for Environmental Life Sciences Engineering, Singapore 637551, Singapore; (M.H.I.); (Y.F.G.); (S.K.); (D.M.)
- The iThree Institute, The University of Technology Sydney, Sydney, NSW 2007, Australia; (P.N.); (I.G.D.)
| | - Scott A. Rice
- Singapore Centre for Environmental Life Sciences Engineering, Singapore 637551, Singapore; (M.H.I.); (Y.F.G.); (S.K.); (D.M.)
- The School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore
- The iThree Institute, The University of Technology Sydney, Sydney, NSW 2007, Australia; (P.N.); (I.G.D.)
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Activation of the type VI secretion system in the squid symbiont Vibrio fischeri requires the transcriptional regulator TasR and the structural proteins TssM and TssA. J Bacteriol 2021; 203:e0039921. [PMID: 34370559 PMCID: PMC8508121 DOI: 10.1128/jb.00399-21] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacteria have evolved diverse strategies to compete for a niche, including the type VI secretion system (T6SS), a contact-dependent killing mechanism. T6SSs are common in bacterial pathogens, commensals, and beneficial symbionts, where they affect the diversity and spatial structure of host-associated microbial communities. Although T6SS gene clusters are often located on genomic islands (GIs), which may be transferred as a unit, the regulatory strategies that promote gene expression once the T6SS genes are transferred into a new cell are not known. We used the squid symbiont, Vibrio fischeri, to identify essential regulatory factors that control expression of a strain-specific T6SS encoded on a GI. We found that a transcriptional reporter for this T6SS is active only in strains that contain the T6SS-encoding GI, suggesting the GI encodes at least one essential regulator. A transposon screen identified seven mutants that could not activate the reporter. These mutations mapped exclusively to three genes on the T6SS-containing GI that encode two essential structural proteins (a TssA-like protein and TssM) and a transcriptional regulator (TasR). Using T6SS reporters, RT-PCR, competition assays, and differential proteomics, we found that all three genes are required for expression of many T6SS components, except for the TssA-like protein and TssM, which are constitutively expressed. Based on these findings, we propose a model whereby T6SS expression requires conserved structural proteins, in addition to the essential regulator TasR, and this ability to self-regulate may be a strategy to activate T6SS expression upon transfer of T6SS-encoding elements into a new bacterial host. Importance Interbacterial weapons like the T6SS are often located on mobile genetic elements and their expression is highly regulated. We found that two conserved structural proteins are required for T6SS expression in Vibrio fischeri. These structural proteins also contain predicted GTPase and GTP binding domains, suggesting their role in promoting T6SS expression may involve sensing the energetic state of the cell. Such a mechanism would provide a direct link between T6SS activation and cellular energy levels, providing a "checkpoint" to ensure the cell has sufficient energy to build such a costly weapon. Because these regulatory factors are encoded within the T6SS gene cluster, they are predicted to move with the genetic element to activate T6SS expression in a new host cell.
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Variability in the Occupancy of Escherichia coli O157 Integration Sites by Shiga Toxin-Encoding Prophages. Toxins (Basel) 2021; 13:toxins13070433. [PMID: 34206386 PMCID: PMC8309913 DOI: 10.3390/toxins13070433] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Revised: 06/18/2021] [Accepted: 06/20/2021] [Indexed: 11/17/2022] Open
Abstract
Escherichia coli O157:H7 strains often produce Shiga toxins encoded by genes on lambdoid bacteriophages that insert into multiple loci as prophages. O157 strains were classified into distinct clades that vary in virulence. Herein, we used PCR assays to examine Shiga toxin (Stx) prophage occupancy in yehV, argW, wrbA, and sbcB among 346 O157 strains representing nine clades. Overall, yehV was occupied in most strains (n = 334, 96.5%), followed by wrbA (n = 213, 61.6%), argW (n = 103, 29.8%), and sbcB (n = 93, 26.9%). Twelve occupancy profiles were identified that varied in frequency and differed across clades. Strains belonging to clade 8 were more likely to have occupied sbcB and argW sites compared to other clades (p < 0.0001), while clade 2 strains were more likely to have occupied wrbA sites (p < 0.0001). Clade 8 strains also had more than the expected number of occupied sites based on the presence of stx variants (p < 0.0001). Deletion of a 20 kb non-Stx prophage occupying yehV in a clade 8 strain resulted in an ~18-fold decrease in stx2 expression. These data highlight the complexity of Stx prophage integration and demonstrate that clade 8 strains, which were previously linked to hemolytic uremic syndrome, have unique Stx prophage occupancy profiles that can impact stx2 expression.
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Rodríguez-Rubio L, Haarmann N, Schwidder M, Muniesa M, Schmidt H. Bacteriophages of Shiga Toxin-Producing Escherichia coli and Their Contribution to Pathogenicity. Pathogens 2021; 10:404. [PMID: 33805526 PMCID: PMC8065619 DOI: 10.3390/pathogens10040404] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 03/18/2021] [Accepted: 03/24/2021] [Indexed: 12/25/2022] Open
Abstract
Shiga toxins (Stx) of Shiga toxin-producing Escherichia coli (STEC) are generally encoded in the genome of lambdoid bacteriophages, which spend the most time of their life cycle integrated as prophages in specific sites of the bacterial chromosome. Upon spontaneous induction or induction by chemical or physical stimuli, the stx genes are co-transcribed together with the late phase genes of the prophages. After being assembled in the cytoplasm, and after host cell lysis, mature bacteriophage particles are released into the environment, together with Stx. As members of the group of lambdoid phages, Stx phages share many genetic features with the archetypical temperate phage Lambda, but are heterogeneous in their DNA sequences due to frequent recombination events. In addition to Stx phages, the genome of pathogenic STEC bacteria may contain numerous prophages, which are either cryptic or functional. These prophages may carry foreign genes, some of them related to virulence, besides those necessary for the phage life cycle. Since the production of one or more Stx is considered the major pathogenicity factor of STEC, we aim to highlight the new insights on the contribution of Stx phages and other STEC phages to pathogenicity.
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Affiliation(s)
- Lorena Rodríguez-Rubio
- Department of Genetics, Microbiology and Statistics, University of Barcelona, Diagonal 643, 08028 Barcelona, Spain; (L.R.-R.); (M.M.)
| | - Nadja Haarmann
- Department of Food Microbiology and Hygiene, Institute of Food Science and Biotechnology, University of Hohenheim, 70599 Stuttgart, Germany; (N.H.); (M.S.)
| | - Maike Schwidder
- Department of Food Microbiology and Hygiene, Institute of Food Science and Biotechnology, University of Hohenheim, 70599 Stuttgart, Germany; (N.H.); (M.S.)
| | - Maite Muniesa
- Department of Genetics, Microbiology and Statistics, University of Barcelona, Diagonal 643, 08028 Barcelona, Spain; (L.R.-R.); (M.M.)
| | - Herbert Schmidt
- Department of Food Microbiology and Hygiene, Institute of Food Science and Biotechnology, University of Hohenheim, 70599 Stuttgart, Germany; (N.H.); (M.S.)
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Sy BM, Tree JJ. Small RNA Regulation of Virulence in Pathogenic Escherichia coli. Front Cell Infect Microbiol 2021; 10:622202. [PMID: 33585289 PMCID: PMC7873438 DOI: 10.3389/fcimb.2020.622202] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Accepted: 12/10/2020] [Indexed: 11/17/2022] Open
Abstract
Enteric and extraintestinal pathotypes of Escherichia coli utilize a wide range of virulence factors to colonize niches within the human body. During infection, virulence factors such as adhesins, secretions systems, or toxins require precise regulation and coordination to ensure appropriate expression. Additionally, the bacteria navigate rapidly changing environments with fluctuations in pH, temperature, and nutrient levels. Enteric pathogens utilize sophisticated, interleaved systems of transcriptional and post-transcriptional regulation to sense and respond to these changes and modulate virulence gene expression. Regulatory small RNAs and RNA-binding proteins play critical roles in the post-transcriptional regulation of virulence. In this review we discuss how the mosaic genomes of Escherichia coli pathotypes utilize small RNA regulation to adapt to their niche and become successful human pathogens.
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Affiliation(s)
- Brandon M Sy
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Jai J Tree
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, Australia
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Differential induction of Shiga toxin in environmental Escherichia coli O145:H28 strains carrying the same genotype as the outbreak strains. Int J Food Microbiol 2020; 339:109029. [PMID: 33360585 DOI: 10.1016/j.ijfoodmicro.2020.109029] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 12/11/2020] [Accepted: 12/14/2020] [Indexed: 02/07/2023]
Abstract
Shiga toxin-producing Escherichia coli (STEC) O145 is a major serotype associated with severe human disease. Production of Shiga toxins (Stxs), especially Stx2a, is thought to be correlated with STEC virulence. Since stx genes are located in prophages genomes, induction of prophages is required for effective Stxs production. Here, we investigated the production of Stxs in 12 environmental STEC O145:H28 strains under stresses STEC encounter in natural habitats and performed comparative analysis with two O145:H28 clinical strains, one linked to a 2010 U.S. lettuce-associated outbreak (RM13514) and the other linked to a 2007 Belgium ice cream-associated outbreak (RM13516). Similar to the outbreak strains, all environmental strains belong to Sequence Type (ST)-78 using the EcMLST typing scheme. Although all Stx1a-prophages were grouped together, variations in Stx1a production were observed prior to or following the inductions. Among all stx2a positive environmental strains, only the Stx2a-prophage in cattle isolate RM9154-C1 was clustered with the Stx2a-prophages in RM13514, the Stx2a-phage induced from a STEC O104:H4 strain linked to the 2011 outbreak of enterohemorrhagic infection in Germany, and the Stx2a-prophage in STEC O157:H7 strain EDL933, a prototype of enterohemorrhagic E. coli. Furthermore, the Stx2a-prophage in RM9154-C1 shared the same chromosomal insertion site and carried the same antiterminator Q gene and the late promoter PR' as the Stx2a-prophage in RM13514. Following mitomycin C or enrofloxacin treatment, the production of Stx2a in RM9154-C1 was the highest among all environmental strains tested. In contrast, following acid challenge and recovery, the production of Stx2a in RM9154-C1 was the lowest among all the environmental strains tested, at a level comparable to the clinical strains. A significant increase in Stx2a production was detected in all strains when exposed to H2O2, although the induction fold was much lower than those by other inducers. This low-efficiency induction of Stx-prophages by H2O2, a natural inducer of Stx-prophages, supports the hypothesis of bacterial altruism in controlling Stxs production, a strategy that assures the survival of the STEC population as a whole by sacrificing a small fraction of cells for Stxs production and release. Differential induction of Stxs among strains carrying nearly identical Stx-prophages suggests a role of host bacteria in regulating Stxs production. Our study revealed diverse Stx-prophages in STEC O145:H28 strains that were genotypically indistinguishable. Identification of a cattle isolate harboring a Stx2a-prophage associated with high virulence supports the premise that cattle, a natural reservoir of STEC, serve as a source of hypervirulent STEC strains.
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A Toxic Environment: a Growing Understanding of How Microbial Communities Affect Escherichia coli O157:H7 Shiga Toxin Expression. Appl Environ Microbiol 2020; 86:AEM.00509-20. [PMID: 32358004 DOI: 10.1128/aem.00509-20] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Enterohemorrhagic Escherichia coli (EHEC) strains, including E. coli O157:H7, cause severe illness in humans due to the production of Shiga toxin (Stx) and other virulence factors. Because Stx is coregulated with lambdoid prophage induction, its expression is especially susceptible to environmental cues. Infections with Stx-producing E. coli can be difficult to model due to the wide range of disease outcomes: some infections are relatively mild, while others have serious complications. Probiotic organisms, members of the gut microbiome, and organic acids can depress Stx production, in many cases by inhibiting the growth of EHEC strains. On the other hand, the factors currently known to amplify Stx act via their effect on the stx-converting phage. Here, we characterize two interactive mechanisms that increase Stx production by O157:H7 strains: first, direct interactions with phage-susceptible E. coli, and second, indirect amplification by secreted factors. Infection of susceptible strains by the stx-converting phage can expand the Stx-producing population in a human or animal host, and phage infection has been shown to modulate virulence in vitro and in vivo Acellular factors, particularly colicins and microcins, can kill O157:H7 cells but may also trigger Stx expression in the process. Colicins, microcins, and other bacteriocins have diverse cellular targets, and many such molecules remain uncharacterized. The identification of additional Stx-amplifying microbial interactions will improve our understanding of E. coli O157:H7 infections and help elucidate the intricate regulation of pathogenicity in EHEC strains.
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Abstract
Enterohemorrhagic E. coli is a significant human pathogen that can cause severe disease due to the release of Shiga toxins. The toxins are encoded within lysogenic bacteriophage and controlled by antitermination of the phage late promoter, PR′. This promoter is always active, but terminated immediately downstream during lysogeny. A byproduct of antitermination regulation is transcription of a short RNA that is thought to be nonfunctional. Here we demonstrate that in Shiga toxin-encoding phages, this short RNA is a Hfq-binding regulatory small RNA. The small RNA represses toxin production threefold under lysogenic conditions and promotes high cell density growth. Lysogenic bacteriophages are highly abundant and our results suggest that antiterminated phage promoters may be a rich source of regulatory RNAs. Enterohemorrhagic Escherichia coli is a significant human pathogen that causes disease ranging from hemorrhagic colitis to hemolytic uremic syndrome. The latter can lead to potentially fatal renal failure and is caused by the release of Shiga toxins that are encoded within lambdoid bacteriophages. The toxins are encoded within the late transcript of the phage and are regulated by antitermination of the PR′ late promoter during lytic induction of the phage. During lysogeny, the late transcript is prematurely terminated at tR′ immediately downstream of PR′, generating a short RNA that is a byproduct of antitermination regulation. We demonstrate that this short transcript binds the small RNA chaperone Hfq, and is processed into a stable 74-nt regulatory small RNA that we have termed StxS. StxS represses expression of Shiga toxin 1 under lysogenic conditions through direct interactions with the stx1AB transcript. StxS acts in trans to activate expression of the general stress response sigma factor, RpoS, through direct interactions with an activating seed sequence within the 5′ UTR. Activation of RpoS promotes high cell density growth under nutrient-limiting conditions. Many phages utilize antitermination to regulate the lytic/lysogenic switch and our results demonstrate that short RNAs generated as a byproduct of this regulation can acquire regulatory small RNA functions that modulate host fitness.
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Stanton E, Wahlig TA, Park D, Kaspar CW. Chronological set of E. coli O157:H7 bovine strains establishes a role for repeat sequences and mobile genetic elements in genome diversification. BMC Genomics 2020; 21:562. [PMID: 32807088 PMCID: PMC7430833 DOI: 10.1186/s12864-020-06943-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Accepted: 07/23/2020] [Indexed: 11/21/2022] Open
Abstract
Background Enterohemorrhagic Escherichia coli O157:H7 (EHEC) is a significant foodborne pathogen that resides asymptomatically within cattle and other ruminants. The EHEC genome harbors an extensive collection of mobile genetic elements (MGE), including multiple prophage, prophage-like elements, plasmids, and insertion sequence (IS) elements. Results A chronological collection of EHEC strains (FRIK804, FRIK1275, and FRIK1625) isolated from a Wisconsin dairy farm (farm X) comprised a closely related clade genetically differentiated by structural alterations to the chromosome. Comparison of the FRIK804 genome with a reference EHEC strain Sakai found a unique prophage like element (PLE, indel 1) and an inversion (1.15 Mb) situated symmetrically with respect to the terminus region. Detailed analysis determined the inversion was due to homologous recombination between repeat sequences in prophage. The three farm X strains were distinguished by the presence or absence of indel 3 (61 kbp) and indel 4 (48 kbp); FRIK804 contained both of these regions, FRIK1275 lacked indel 4, and indels 3 and 4 were both absent in FRIK1625. Indel 3 was the stx2 prophage and indel 4 involved a deletion between two adjacent prophage with shared repeat sequences. Both FRIK804 and FRIK1275 produced functional phage while FRIK1625 did not, which is consistent with indel 3. Due to their involvement in recombination events, direct and inverted repeat sequences were identified, and their locations mapped to the chromosome. FRIK804 had a greater number and overall length of repeat sequences than E. coli K12 strain MG1655. Repeat sequences were most commonly associated with MGE. Conclusions This research demonstrated that three EHEC strains from a Wisconsin dairy farm were closely related and distinguished by variability within prophage regions and other MGE. Chromosome alterations were associated with recombination events between repeat sequences. An inventory of direct and inverted repeat sequences found a greater abundance and total length of repeat sequences in the EHEC strains compared to E. coli strain MG1655. The locations of the repeat sequences were biased towards MGE. The findings from this study expand our understanding of the precise molecular events and elements that contributed to genetic diversification of wild-type EHEC in the bovine and farm environments.
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Affiliation(s)
- Eliot Stanton
- Department of Bacteriology, University of Wisconsin-Madison, Microbial Sciences Building, 1550 Linden Drive, Madison, WI, 53706, USA
| | - Taylor A Wahlig
- Department of Bacteriology, University of Wisconsin-Madison, Microbial Sciences Building, 1550 Linden Drive, Madison, WI, 53706, USA.,University of Utah, School of Medicine, 30 N 1900 E, Salt Lake City, UT, 84132, USA
| | - Dongjin Park
- Food Science and Technology Department, University of Nebraska-Lincoln, Lincoln, NE, USA
| | - Charles W Kaspar
- Department of Bacteriology, University of Wisconsin-Madison, Microbial Sciences Building, 1550 Linden Drive, Madison, WI, 53706, USA. .,Food Research Institute, University of Wisconsin-Madison, Microbial Sciences Building, 1550 Linden Drive, Madison, WI, 53706, USA.
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Miura S, Tamamura Y, Takayasu M, Sasaki M, Nishimura N, Tokugawa K, Suwa I, Murata R, Akiba M, Kusumoto M, Uchida I. Influence of SOS-inducing agents on the expression of ArtAB toxin gene in Salmonella enterica and Salmonella bongori. MICROBIOLOGY-SGM 2020; 166:785-793. [PMID: 32579098 DOI: 10.1099/mic.0.000939] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Salmonella enterica subspecies enterica serovar Typhimurium (S. Typhimurium) definitive phage type 104 (DT104), S. enterica subspecies enterica serovar Worthington (S. Worthington) and S. bongori produce ArtA and ArtB (ArtAB) toxin homologues, which catalyse ADP-ribosylation of pertussis toxin-sensitive G protein. ArtAB gene (artAB) is encoded on prophage in DT104 and its expression is induced by mitomycin C (MTC) and hydrogen peroxide (H2O2) that trigger the bacterial SOS response. Although the genetic regulatory mechanism associated with artAB expression is not characterized, it is thought to be associated with prophage induction, which occurs when the RecA-mediated SOS response is triggered. Here we show that subinhibitory concentration of quinolone antibiotics that are SOS-inducing agents, also induce ArtAB production in these Salmonella strains. Both MTC and fluoroquinolone antibiotics such as enrofloxacin-induced artA and recA transcription and artAB-encoding prophage (ArtAB-prophage) in DT104 and S. Worthington. However, in S. bongori, which harbours artAB genes on incomplete prophage, artA transcription was induced by MTC and enrofloxacin, but prophage induction was not observed. Taken together, these results suggest that SOS response followed by induction of artAB transcription is essential for ArtAB production. H2O2-mediated induction of ArtAB prophage and efficient production of ArtAB was observed in DT104 but not in S. Worthington and S. bongori. Therefore, induction of artAB expression with H2O2 is strain-specific, and the mode of action of H2O2 as an SOS-inducing agent might be different from those of MTC and quinolone antibiotics.
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Affiliation(s)
- Shou Miura
- Veterinary Bacteriology, Department of Pathobiology, School of Veterinary Medicine, Rakuno Gakuen University, 582, Bunkyodai-Midorimachi, EbetsuHokkaido, 069-8501, Japan
| | - Yukino Tamamura
- Division of Bacterial and Parasitic Disease, National Institute of Animal Health, Tsukuba, Ibaraki, 305-0856, Japan
| | - Mariko Takayasu
- Ibaraki Kenhoku Livestock Hygiene Service Center, 996-1 Nakagachi, Mito, Ibaraki 310-0002, Japan.,Division of Bacterial and Parasitic Disease, National Institute of Animal Health, Tsukuba, Ibaraki, 305-0856, Japan
| | - Miwa Sasaki
- Veterinary Bacteriology, Department of Pathobiology, School of Veterinary Medicine, Rakuno Gakuen University, 582, Bunkyodai-Midorimachi, EbetsuHokkaido, 069-8501, Japan
| | - Natsuko Nishimura
- Veterinary Bacteriology, Department of Pathobiology, School of Veterinary Medicine, Rakuno Gakuen University, 582, Bunkyodai-Midorimachi, EbetsuHokkaido, 069-8501, Japan
| | - Kanetaka Tokugawa
- Veterinary Bacteriology, Department of Pathobiology, School of Veterinary Medicine, Rakuno Gakuen University, 582, Bunkyodai-Midorimachi, EbetsuHokkaido, 069-8501, Japan
| | - Izumi Suwa
- Veterinary Bacteriology, Department of Pathobiology, School of Veterinary Medicine, Rakuno Gakuen University, 582, Bunkyodai-Midorimachi, EbetsuHokkaido, 069-8501, Japan
| | - Ryo Murata
- Veterinary Bacteriology, Department of Pathobiology, School of Veterinary Medicine, Rakuno Gakuen University, 582, Bunkyodai-Midorimachi, EbetsuHokkaido, 069-8501, Japan
| | - Masato Akiba
- Division of Bacterial and Parasitic Disease, National Institute of Animal Health, Tsukuba, Ibaraki, 305-0856, Japan
| | - Masahiro Kusumoto
- Division of Bacterial and Parasitic Disease, National Institute of Animal Health, Tsukuba, Ibaraki, 305-0856, Japan
| | - Ikuo Uchida
- Veterinary Bacteriology, Department of Pathobiology, School of Veterinary Medicine, Rakuno Gakuen University, 582, Bunkyodai-Midorimachi, EbetsuHokkaido, 069-8501, Japan
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l-Arginine sensing regulates virulence gene expression and disease progression in enteric pathogens. Proc Natl Acad Sci U S A 2020; 117:12387-12393. [PMID: 32409599 DOI: 10.1073/pnas.1919683117] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Microbiota, host and dietary metabolites/signals compose the rich gut chemical environment, which profoundly impacts virulence of enteric pathogens. Enterohemorrhagic Escherichia coli (EHEC) engages a syringe-like machinery named type-III secretion system (T3SS) to inject effectors within host cells that lead to intestinal colonization and disease. We previously conducted a high-throughput screen to identify metabolic pathways that affect T3SS expression. Here we show that in the presence of arginine, the arginine sensor ArgR, identified through this screen, directly activates expression of the genes encoding the T3SS. Exogenously added arginine induces EHEC virulence gene expression in vitro. Congruently, a mutant deficient in arginine transport (ΔartP) had decreased virulence gene expression. ArgR also augments murine disease caused by Citrobacter rodentium, which is a murine pathogen extensively employed as a surrogate animal model for EHEC. The source of arginine sensed by C. rodentium is not dietary. At the peak of C. rodentium infection, increased arginine concentration in the colon correlated with down-regulation of the host SLC7A2 transporter. This increase in the concentration of colonic arginine promotes virulence gene expression in C. rodentium Arginine is an important modulator of the host immune response to pathogens. Here we add that arginine also directly impacts bacterial virulence. These findings suggest that a delicate balance between host and pathogen responses to arginine occur during disease progression.
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Baraketi A, D'Auria S, Shankar S, Fraschini C, Salmieri S, Menissier J, Lacroix M. Novel spider web trap approach based on chitosan/cellulose nanocrystals/glycerol membrane for the detection of Escherichia coli O157:H7 on food surfaces. Int J Biol Macromol 2020; 146:1009-1014. [DOI: 10.1016/j.ijbiomac.2019.09.225] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Revised: 09/23/2019] [Accepted: 09/26/2019] [Indexed: 12/14/2022]
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Abstract
With the increasing frequency of antibiotic resistance, it is critical to explore new therapeutic strategies for treating bacterial infections. Here, we use a temperate phage, i.e., one that integrates itself into the bacterial genome, to neutralize the expression of a virulence factor by modifying bacterial function at the genetic level. We show that Shiga toxin production can be significantly reduced in vitro and in the mammalian gut. Alternative to traditional applications of phage therapy that rely on killing bacteria, our genetics-based antivirulence approach introduces a new framework for treating bacterial infections. Elimination or alteration of select members of the gut microbiota is key to therapeutic efficacy. However, the complexity of these microbial inhabitants makes it challenging to precisely target bacteria. Here, we deliver exogenous genes to specific bacteria by genomic integration of temperate phage for long-lasting modification. As a real-world therapeutic test, we engineered λ phage to transcriptionally repress Shiga toxin by using genetic hybrids between λ and other lambdoid phages to overcome resistance encoded by the virulence-expressing prophage. We show that a single dose of engineered phage propagates throughout the bacterial community and reduces Shiga toxin production in an enteric mouse model of infection without markedly affecting bacterial concentrations. Our work reveals a new framework for transferring functions to bacteria within their native environment. IMPORTANCE With the increasing frequency of antibiotic resistance, it is critical to explore new therapeutic strategies for treating bacterial infections. Here, we use a temperate phage, i.e., one that integrates itself into the bacterial genome, to neutralize the expression of a virulence factor by modifying bacterial function at the genetic level. We show that Shiga toxin production can be significantly reduced in vitro and in the mammalian gut. Alternative to traditional applications of phage therapy that rely on killing bacteria, our genetics-based antivirulence approach introduces a new framework for treating bacterial infections.
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30
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Dydecka A, Bloch S, Necel A, Topka G, Węgrzyn A, Tong J, Donaldson LW, Węgrzyn G, Nejman-Faleńczyk B. The ea22 gene of lambdoid phages: preserved prolysogenic function despite of high sequence diversity. Virus Genes 2020; 56:266-277. [PMID: 31970620 PMCID: PMC7093339 DOI: 10.1007/s11262-020-01734-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Accepted: 01/14/2020] [Indexed: 12/22/2022]
Abstract
The exo-xis region of lambdoid phages contains open reading frames and genes that appear to be evolutionarily important. However, this region has received little attention up to now. In this study, we provided evidence that ea22, the largest gene of this region, favors the lysogenic pathway over the lytic pathway in contrast to other characterized exo-xis region genes including ea8.5, orf61, orf60a, and orf63. Our assays also suggest some functional analogies between Ea22 and the phage integrase protein (Int). While it is unsurprising that Ea22 operates similarly in both λ and Stx phages, we have observed some distinctions that may arise from considerable sequence dissimilarity at the carboxy termini of each protein.
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Affiliation(s)
- Aleksandra Dydecka
- Department of Molecular Biology, Faculty of Biology, University of Gdańsk, Wita Stwosza 59, 80-308, Gdańsk, Poland
| | - Sylwia Bloch
- Laboratory of Molecular Biology, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Kładki 24, 80-822, Gdańsk, Poland
| | - Agnieszka Necel
- Department of Molecular Biology, Faculty of Biology, University of Gdańsk, Wita Stwosza 59, 80-308, Gdańsk, Poland
| | - Gracja Topka
- Department of Molecular Biology, Faculty of Biology, University of Gdańsk, Wita Stwosza 59, 80-308, Gdańsk, Poland
| | - Alicja Węgrzyn
- Laboratory of Molecular Biology, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Kładki 24, 80-822, Gdańsk, Poland
| | - Jinge Tong
- Department of Biology, York University, 4700 Keele Street, Toronto, ON, M3J 1P3, Canada
| | - Logan W Donaldson
- Department of Biology, York University, 4700 Keele Street, Toronto, ON, M3J 1P3, Canada
| | - Grzegorz Węgrzyn
- Department of Molecular Biology, Faculty of Biology, University of Gdańsk, Wita Stwosza 59, 80-308, Gdańsk, Poland
| | - Bożena Nejman-Faleńczyk
- Department of Molecular Biology, Faculty of Biology, University of Gdańsk, Wita Stwosza 59, 80-308, Gdańsk, Poland.
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Role of Shiga Toxins in Cytotoxicity and Immunomodulatory Effects of Escherichia coli O157:H7 during Host-Bacterial Interactions in vitro. Toxins (Basel) 2020; 12:toxins12010048. [PMID: 31947665 PMCID: PMC7020462 DOI: 10.3390/toxins12010048] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2019] [Revised: 01/10/2020] [Accepted: 01/11/2020] [Indexed: 12/19/2022] Open
Abstract
Enterohemorrhagic Escherichia coli (EHEC) strains are food-borne pathogens that can cause different clinical conditions. Shiga toxin 2a and/or 2c (Stx2)-producing E. coli O157:H7 is the serotype most frequently associated with severe human disease. In this work we analyzed the hypothesis that host cells participate in Stx2 production, cell damage, and inflammation during EHEC infection. With this aim, macrophage-differentiated THP-1 cells and the intestinal epithelial cell line HCT-8 were incubated with E. coli O157:H7. A time course analysis of cellular and bacterial survival, Stx2 production, stx2 transcription, and cytokine secretion were analyzed in both human cell lines. We demonstrated that macrophages are able to internalize and kill EHEC. Simultaneously, Stx2 produced by internalized bacteria played a major role in macrophage death. In contrast, HCT-8 cells were completely resistant to EHEC infection. Besides, macrophages and HCT-8 infected cells produce IL-1β and IL-8 inflammatory cytokines, respectively. At the same time, bacterial stx2-specific transcripts were detected only in macrophages after EHEC infection. The interplay between bacteria and host cells led to Stx production, triggering of inflammatory response and cell damage, all of which could contribute to a severe outcome after EHEC infections.
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32
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Yang X, Bai X, Zhang J, Sun H, Fu S, Fan R, He X, Scheutz F, Matussek A, Xiong Y. Escherichia coli strains producing a novel Shiga toxin 2 subtype circulate in China. Int J Med Microbiol 2019; 310:151377. [PMID: 31757694 DOI: 10.1016/j.ijmm.2019.151377] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Revised: 09/25/2019] [Accepted: 10/29/2019] [Indexed: 11/16/2022] Open
Abstract
Shiga toxin (Stx) is the key virulence factor in Shiga toxin producing Escherichia coli (STEC), which can cause diarrhea and hemorrhagic colitis with life-threatening complications. Stx comprises two toxin types, Stx1 and Stx2. Several Stx1/Stx2 subtypes have been identified in E. coli, which are variable in sequences, toxicity and host specificity. Here, we report the identification of a novel Stx2 subtype, designated Stx2k, in E. coli strains widely detected from diarrheal patients, animals, and raw meats in China over time. Stx2k exhibits varied cytotoxicity in vitro among individual strains. The Stx2k converting prophages displayed considerable heterogeneity in terms of insertion site, genetic content and structure. Whole genome analysis revealed that the stx2k-containing strains were genetically heterogeneous with diverse serotypes, sequence types, and virulence gene profiles. The nine stx2k-containing strains formed two major phylogenetic clusters closely with strains belonging to STEC, enterotoxigenic E. coli (ETEC), and STEC/ETEC hybrid. One stx2k-containing strain harbored one plasmid-encoded heat-stable enterotoxin sta gene and two identical copies of chromosome-encoded stb gene, exhibiting STEC/ETEC hybrid pathotype. Our finding enlarges the pool of Stx2 subtypes and highlights the extraordinary genomic plasticity of STEC strains. Given the wide distribution of the Stx2k-producing strains in diverse sources and their pathogenic potential, Stx2k should be taken into account in epidemiological surveillance of STEC infections and clinical diagnosis.
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Affiliation(s)
- Xi Yang
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Changping, Beijing, China
| | - Xiangning Bai
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Changping, Beijing, China; Division of Clinical Microbiology, Department of Laboratory Medicine, Karolinska Institutet, Karolinska University Hospital, Huddinge, Sweden
| | - Ji Zhang
- EpiLab, New Zealand Food Safety Science & Research Centre, School of Veterinary Science, Massey University, New Zealand
| | - Hui Sun
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Changping, Beijing, China
| | - Shanshan Fu
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Changping, Beijing, China
| | - Ruyue Fan
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Changping, Beijing, China
| | - Xiaohua He
- Western Regional Research Center, U.S. Department of Agriculture, Agricultural Research Service, Albany, CA, USA
| | - Flemming Scheutz
- The International Centre for Reference and Research on Escherichia and Klebsiella, Unit of Foodborne Bacteria and Typing, Department of Bacteria, Parasites and Fungi, Statens Serum Institut, Copenhagen, Denmark
| | - Andreas Matussek
- Division of Clinical Microbiology, Department of Laboratory Medicine, Karolinska Institutet, Karolinska University Hospital, Huddinge, Sweden
| | - Yanwen Xiong
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Changping, Beijing, China; Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Hangzhou, Zhejiang Province, China.
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Response to Questions Posed by the Food and Drug Administration Regarding Virulence Factors and Attributes that Define Foodborne Shiga Toxin-Producing Escherichia coli (STEC) as Severe Human Pathogens †. J Food Prot 2019; 82:724-767. [PMID: 30969806 DOI: 10.4315/0362-028x.jfp-18-479] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
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- NACMCF Executive Secretariat, * U.S. Department of Agriculture, Food Safety and Inspection Service, Office of Public Health Science, PP3, 9-178, 1400 Independence Avenue S.W., Washington, D.C. 20250-3700, USA
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Rowan-Nash AD, Korry BJ, Mylonakis E, Belenky P. Cross-Domain and Viral Interactions in the Microbiome. Microbiol Mol Biol Rev 2019; 83:e00044-18. [PMID: 30626617 PMCID: PMC6383444 DOI: 10.1128/mmbr.00044-18] [Citation(s) in RCA: 77] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The importance of the microbiome to human health is increasingly recognized and has become a major focus of recent research. However, much of the work has focused on a few aspects, particularly the bacterial component of the microbiome, most frequently in the gastrointestinal tract. Yet humans and other animals can be colonized by a wide array of organisms spanning all domains of life, including bacteria and archaea, unicellular eukaryotes such as fungi, multicellular eukaryotes such as helminths, and viruses. As they share the same host niches, they can compete with, synergize with, and antagonize each other, with potential impacts on their host. Here, we discuss these major groups making up the human microbiome, with a focus on how they interact with each other and their multicellular host.
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Affiliation(s)
- Aislinn D Rowan-Nash
- Department of Molecular Microbiology and Immunology, Brown University, Providence, Rhode Island, USA
| | - Benjamin J Korry
- Department of Molecular Microbiology and Immunology, Brown University, Providence, Rhode Island, USA
| | - Eleftherios Mylonakis
- Infectious Diseases Division, Warren Alpert Medical School of Brown University, Rhode Island Hospital, Providence, Rhode Island, USA
| | - Peter Belenky
- Department of Molecular Microbiology and Immunology, Brown University, Providence, Rhode Island, USA
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The SOS Response Mediates Sustained Colonization of the Mammalian Gut. Infect Immun 2019; 87:IAI.00711-18. [PMID: 30510108 DOI: 10.1128/iai.00711-18] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Accepted: 11/26/2018] [Indexed: 12/12/2022] Open
Abstract
Bacteria have a remarkable ability to survive, persist, and ultimately adapt to environmental challenges. A ubiquitous environmental hazard is DNA damage, and most bacteria have evolved a network of genes to combat genotoxic stress. This network is known as the SOS response and aids in bacterial survival by regulating genes involved in DNA repair and damage tolerance. Recently, the SOS response has been shown to play an important role in bacterial pathogenesis, and yet the role of the SOS response in nonpathogenic organisms and in physiological settings remains underexplored. Using a commensal Escherichia coli strain, MP1, we showed that the SOS response plays a vital role during colonization of the murine gut. In an unperturbed environment, the SOS-off mutant is impaired for stable colonization relative to a wild-type strain, suggesting the presence of genotoxic stress in the mouse gut. We evaluated the possible origins of genotoxic stress in the mouse gut by examining factors associated with the host versus the competing commensal organisms. In a dextran sulfate sodium (DSS) colitis model, the SOS-off colonization defect persisted but was not exacerbated. In contrast, in a germ-free model, the SOS-off mutant colonized with efficiency equal to that seen with the wild-type strain, suggesting that competing commensal organisms might be a significant source of genotoxic stress. This report extends our understanding of the importance of a functional SOS response for bacterial fitness in the context of a complex physiological environment and highlights the SOS response as a possible mechanism that contributes to ongoing genomic changes, including potential antibiotic resistance, in the microbiome of healthy hosts.
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Balasubramanian S, Osburne MS, BrinJones H, Tai AK, Leong JM. Prophage induction, but not production of phage particles, is required for lethal disease in a microbiome-replete murine model of enterohemorrhagic E. coli infection. PLoS Pathog 2019; 15:e1007494. [PMID: 30629725 PMCID: PMC6328086 DOI: 10.1371/journal.ppat.1007494] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Accepted: 12/01/2018] [Indexed: 12/12/2022] Open
Abstract
Enterohemorrhagic Escherichia coli (EHEC) colonize intestinal epithelium by generating characteristic attaching and effacing (AE) lesions. They are lysogenized by prophage that encode Shiga toxin 2 (Stx2), which is responsible for severe clinical manifestations. As a lysogen, prophage genes leading to lytic growth and stx2 expression are repressed, whereas induction of the bacterial SOS response in response to DNA damage leads to lytic phage growth and Stx2 production both in vitro and in germ-free or streptomycin-treated mice. Some commensal bacteria diminish prophage induction and concomitant Stx2 production in vitro, whereas it has been proposed that phage-susceptible commensals may amplify Stx2 production by facilitating successive cycles of infection in vivo. We tested the role of phage induction in both Stx production and lethal disease in microbiome-replete mice, using our mouse model encompassing the murine pathogen Citrobacter rodentium lysogenized with the Stx2-encoding phage Φstx2dact. This strain generates EHEC-like AE lesions on the murine intestine and causes lethal Stx-mediated disease. We found that lethal mouse infection did not require that Φstx2dact infect or lysogenize commensal bacteria. In addition, we detected circularized phage genomes, potentially in the early stage of replication, in feces of infected mice, confirming that prophage induction occurs during infection of microbiota-replete mice. Further, C. rodentium (Φstx2dact) mutants that do not respond to DNA damage or express stx produced neither high levels of Stx2 in vitro or lethal infection in vivo, confirming that SOS induction and concomitant expression of phage-encoded stx genes are required for disease. In contrast, C. rodentium (Φstx2dact) mutants incapable of prophage genome excision or of packaging phage genomes retained the ability to produce Stx in vitro, as well as to cause lethal disease in mice. Thus, in a microbiome-replete EHEC infection model, lytic induction of Stx-encoding prophage is essential for lethal disease, but actual phage production is not.
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Affiliation(s)
- Sowmya Balasubramanian
- Department of Molecular Biology and Microbiology at Tufts University School of Medicine, Boston, MA, United States of America
| | - Marcia S. Osburne
- Department of Molecular Biology and Microbiology at Tufts University School of Medicine, Boston, MA, United States of America
| | - Haley BrinJones
- Department of Molecular Biology and Microbiology at Tufts University School of Medicine, Boston, MA, United States of America
| | - Albert K. Tai
- Department of Immunology at Tufts University School of Medicine, Boston, MA, United States of America
| | - John M. Leong
- Department of Molecular Biology and Microbiology at Tufts University School of Medicine, Boston, MA, United States of America
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Role of phage ϕ1 in two strains of Salmonella Rissen, sensitive and resistant to phage ϕ1. BMC Microbiol 2018; 18:208. [PMID: 30526475 PMCID: PMC6286511 DOI: 10.1186/s12866-018-1360-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Accepted: 11/28/2018] [Indexed: 01/21/2023] Open
Abstract
Background The study describes the Salmonella Rissen phage ϕ1 isolated from the ϕ1-sensitive Salmonella Rissen strain RW. The same phage was then used to select the resistant strain RRϕ1+, which can harbour or not ϕ1. Results Following this approach, we found that ϕ1, upon excision from RW cells with mitomycin, behaves as a temperate phage: lyses host cells and generates phage particles; instead, upon spontaneous excision from RRϕ1+ cells, it does not generate phage particles; causes loss of phage resistance; switches the O-antigen from the smooth to the rough phenotype, and favors the transition of Salmonella Rissen from the planktonic to the biofilm growth. The RW and RRϕ1+ strains differ by 10 genes; of these, only two (phosphomannomutase_1 and phosphomannomutase_2; both involved in the mannose synthesis pathway) display significant differences at the expression levels. This result suggests that phage resistance is associated with these two genes. Conclusions Phage ϕ1 displays the unusual property of behaving as template as well as lytic phage. This feature was used by the phage to modulate several phases of Salmonella Rissen lifestyle. Electronic supplementary material The online version of this article (10.1186/s12866-018-1360-z) contains supplementary material, which is available to authorized users.
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38
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Modulation of Enterohaemorrhagic Escherichia coli Survival and Virulence in the Human Gastrointestinal Tract. Microorganisms 2018; 6:microorganisms6040115. [PMID: 30463258 PMCID: PMC6313751 DOI: 10.3390/microorganisms6040115] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Revised: 11/16/2018] [Accepted: 11/18/2018] [Indexed: 01/05/2023] Open
Abstract
Enterohaemorrhagic Escherichia coli (EHEC) is a major foodborne pathogen responsible for human diseases ranging from diarrhoea to life-threatening complications. Survival of the pathogen and modulation of virulence gene expression along the human gastrointestinal tract (GIT) are key features in bacterial pathogenesis, but remain poorly described, due to a paucity of relevant model systems. This review will provide an overview of the in vitro and in vivo studies investigating the effect of abiotic (e.g., gastric acid, bile, low oxygen concentration or fluid shear) and biotic (e.g., gut microbiota, short chain fatty acids or host hormones) parameters of the human gut on EHEC survival and/or virulence (especially in relation with motility, adhesion and toxin production). Despite their relevance, these studies display important limitations considering the complexity of the human digestive environment. These include the evaluation of only one single digestive parameter at a time, lack of dynamic flux and compartmentalization, and the absence of a complex human gut microbiota. In a last part of the review, we will discuss how dynamic multi-compartmental in vitro models of the human gut represent a novel platform for elucidating spatial and temporal modulation of EHEC survival and virulence along the GIT, and provide new insights into EHEC pathogenesis.
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Howard-Varona C, Vik DR, Solonenko NE, Li YF, Gazitua MC, Chittick L, Samiec JK, Jensen AE, Anderson P, Howard-Varona A, Kinkhabwala AA, Abedon ST, Sullivan MB. Fighting Fire with Fire: Phage Potential for the Treatment of E. coli O157 Infection. Antibiotics (Basel) 2018; 7:E101. [PMID: 30453470 PMCID: PMC6315980 DOI: 10.3390/antibiotics7040101] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Revised: 11/09/2018] [Accepted: 11/14/2018] [Indexed: 02/07/2023] Open
Abstract
Hemolytic⁻uremic syndrome is a life-threating disease most often associated with Shiga toxin-producing microorganisms like Escherichia coli (STEC), including E. coli O157:H7. Shiga toxin is encoded by resident prophages present within this bacterium, and both its production and release depend on the induction of Shiga toxin-encoding prophages. Consequently, treatment of STEC infections tend to be largely supportive rather than antibacterial, in part due to concerns about exacerbating such prophage induction. Here we explore STEC O157:H7 prophage induction in vitro as it pertains to phage therapy-the application of bacteriophages as antibacterial agents to treat bacterial infections-to curtail prophage induction events, while also reducing STEC O157:H7 presence. We observed that cultures treated with strictly lytic phages, despite being lysed, produce substantially fewer Shiga toxin-encoding temperate-phage virions than untreated STEC controls. We therefore suggest that phage therapy could have utility as a prophylactic treatment of individuals suspected of having been recently exposed to STEC, especially if prophage induction and by extension Shiga toxin production is not exacerbated.
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Affiliation(s)
| | - Dean R Vik
- Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA.
| | - Natalie E Solonenko
- Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA.
| | - Yueh-Fen Li
- Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA.
| | - M Consuelo Gazitua
- Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA.
| | - Lauren Chittick
- Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA.
| | - Jennifer K Samiec
- Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA.
| | - Aubrey E Jensen
- Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA.
| | - Paige Anderson
- Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA.
| | | | | | - Stephen T Abedon
- Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA.
| | - Matthew B Sullivan
- Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA.
- Department of Civil, Environmental and Geodetic Engineering, The Ohio State University, Columbus, OH 43210, USA.
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Zhang LX, Simpson DJ, McMullen LM, Gänzle MG. Comparative Genomics and Characterization of the Late Promoter pR' from Shiga Toxin Prophages in Escherichia coli. Viruses 2018; 10:v10110595. [PMID: 30384416 PMCID: PMC6266700 DOI: 10.3390/v10110595] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2018] [Revised: 10/26/2018] [Accepted: 10/27/2018] [Indexed: 02/02/2023] Open
Abstract
Shiga-toxin producing Escherichia coli (STEC) causes human illness ranging from mild diarrhea to death. The bacteriophage encoded stx genes are located in the late transcription region, downstream of the antiterminator Q. The transcription of the stx genes is directly under the control of the late promoter pR’, thus the sequence diversity of the region between Q and stx, here termed the pR’ region, may affect Stx toxin production. Here, we compared the gene structure of the pR’ region and the stx subtypes of nineteen STECs. The sequence alignment and phylogenetic analysis suggested that the pR’ region tends to be more heterogeneous than the promoter itself, even if the prophages harbor the same stx subtype. Furthermore, we established and validated transcriptional fusions of the pR’ region to the DsRed reporter gene using mitomycin C (MMC) induction. Finally, these constructs were transformed into native and non-native strains and examined with flow cytometry. The results showed that induction levels changed when pR’ regions were placed under different regulatory systems. Moreover, not every stx gene could be induced in its native host bacteria. In addition to the functional genes, the diversity of the pR’ region plays an important role in determining the level of toxin induction.
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Affiliation(s)
- Ling Xiao Zhang
- Department of Agriculture, Food and Nutritional Science, University of Alberta, Edmonton, AB T6G 2P5, Canada.
| | - David J Simpson
- Department of Agriculture, Food and Nutritional Science, University of Alberta, Edmonton, AB T6G 2P5, Canada.
| | - Lynn M McMullen
- Department of Agriculture, Food and Nutritional Science, University of Alberta, Edmonton, AB T6G 2P5, Canada.
| | - Michael G Gänzle
- Department of Agriculture, Food and Nutritional Science, University of Alberta, Edmonton, AB T6G 2P5, Canada.
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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: 4.6] [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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Koskella B, Taylor TB. Multifaceted Impacts of Bacteriophages in the Plant Microbiome. ANNUAL REVIEW OF PHYTOPATHOLOGY 2018; 56:361-380. [PMID: 29958076 DOI: 10.1146/annurev-phyto-080417-045858] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Plant-associated bacteria face multiple selection pressures within their environments and have evolved countless adaptations that both depend on and shape bacterial phenotype and their interaction with plant hosts. Explaining bacterial adaptation and evolution therefore requires considering each of these forces independently as well as their interactions. In this review, we examine how bacteriophage viruses (phages) can alter the ecology and evolution of plant-associated bacterial populations and communities. This includes influencing a bacterial population's response to both abiotic and biotic selection pressures and altering ecological interactions within the microbiome and between the bacteria and host plant. We outline specific ways in which phages can alter bacterial phenotype and discuss when and how this might impact plant-microbe interactions, including for plant pathogens. Finally, we highlight key open questions in phage-bacteria-plant research and offer suggestions for future study.
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Affiliation(s)
- Britt Koskella
- Department of Integrative Biology, University of California, Berkeley, California 94720, USA;
| | - Tiffany B Taylor
- The Milner Centre for Evolution and Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, United Kingdom;
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Sulfamethoxazole - Trimethoprim represses csgD but maintains virulence genes at 30°C in a clinical Escherichia coli O157:H7 isolate. PLoS One 2018; 13:e0196271. [PMID: 29718957 PMCID: PMC5931665 DOI: 10.1371/journal.pone.0196271] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Accepted: 04/10/2018] [Indexed: 12/22/2022] Open
Abstract
The high frequency of prophage insertions in the mlrA gene of clinical serotype O157:H7 isolates renders such strains deficient in csgD-dependent biofilm formation but prophage induction may restore certain mlrA properties. In this study we used transcriptomics to study the effect of high and low sulfamethoxazole–trimethoprim (SMX-TM) concentrations on prophage induction, biofilm regulation, and virulence gene expression in strain PA20 under environmental conditions following 5-hour and 12-hour exposures in broth or on agar. SMX-TM at a sub-lethal concentration induced strong RecA expression resulting in concentration- and time-dependent major transcriptional shifts with emphasis on up-regulation of genes within horizontally-transferred chromosomal regions (HTR). Neither high or low levels of SMX-TM stimulated csgD expression at either time point, but both levels resulted in slight repression. Full expression of Ler-dependent genes paralleled expression of group 1 pch homologues in the presence of high glrA. Finally, stx2 expression, which is strongly dependent on prophage induction, was enhanced at 12 hours but repressed at five hours, in spite of early SOS initiation by the high SMX-TM concentration. Our findings indicate that, similar to host conditions, exposure to environmental conditions increased the expression of virulence genes in a clinical isolate but genes involved in the protective biofilm response were repressed.
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44
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Thuraisamy T, Lodato PB. Influence of RNase E deficiency on the production of stx2-bearing phages and Shiga toxin in an RNase E-inducible strain of enterohaemorrhagic Escherichia coli (EHEC) O157:H7. J Med Microbiol 2018; 67:724-732. [PMID: 29620505 PMCID: PMC7001489 DOI: 10.1099/jmm.0.000728] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Accepted: 03/21/2018] [Indexed: 12/14/2022] Open
Abstract
PURPOSE In enterohaemorrhagic Escherichia coli (EHEC), stx1 or stx2 genes encode Shiga toxin (Stx1 or Stx2, respectively) and are carried by prophages. The production and release of both stx phages and toxin occur upon initiation of the phage lytic cycle. Phages can further disseminate stx genes by infecting naïve bacteria in the intestine. Here, the effect of RNase E deficiency on these two virulence traits was investigated. METHODOLOGY Cultures of the EHEC strains TEA028-rne containing low versus normal RNase E levels or the parental strain (TEA028) were treated with mitomycin C (MMC) to induce the phage lytic cycle. Phages and Stx2 titres were quantified by the double-agar assay and the receptor ELISA technique, respectively. RESULTS RNase E deficiency in MMC-treated cells significantly reduced the yield of infectious stx2 phages. Delayed cell lysis and the appearance of encapsidated phage DNA copies suggest a slow onset of the lytic cycle. However, these observations do not entirely explain the decrease of phage yields. stx1 phages were not detected under normal or deficient RNase E levels. After an initial delay, high levels of toxin were finally produced in MMC-treated cultures. CONCLUSION RNase E scarcity reduces stx2 phage production but not toxin. Normal concentrations of RNase E are likely required for correct phage morphogenesis. Our future work will address the mechanism of RNase E action on phage morphogenesis.
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Pianciola L, Rivas M. Genotypic Features of Clinical and Bovine Escherichia coli O157 Strains Isolated in Countries with Different Associated-Disease Incidences. Microorganisms 2018; 6:microorganisms6020036. [PMID: 29702577 PMCID: PMC6027531 DOI: 10.3390/microorganisms6020036] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 04/20/2018] [Accepted: 04/25/2018] [Indexed: 01/19/2023] Open
Abstract
There is great geographical variation in the frequency of Escherichia coli O157 infections that correlates with important differences in the bovine reservoir of each country. Our group carried out a broad molecular characterization of human and bovine E. coli O157 strains circulating in Argentina using different methodologies. Our data allows us to conclude that in Argentina, a high homogeneity is observed in both cattle and human strains, with almost exclusive circulation of strains belonging to the hypervirulent clade 8 described by Manning. The aim of this review was to compare the genetic background of E. coli O157 strains isolated in countries that have conducted similar studies, to try to correlate specific O157 genotypes with the incidence and severity of E. coli O157 associated diseases. The characteristics of the strains that cause disease in humans reflect the predominant genotypes in cattle in each of the countries analyzed. The main features clearly linked to high incidence or severity of E. coli O157 infections are lineage-specific polymorphism assay-6 lineage I/II, clade 8 strains and probably, clade 6 strains, the stx2a/stx2c genotype, the presence of q933 and q21 simultaneously, and putative virulence factor EC_3286. In countries with an absence of these features in O157 strains, the overall incidence of O157 disease is low. Argentina, where these characteristics are detected in most strains, shows the highest incidence of hemolytic uremic syndrome (HUS) worldwide.
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Affiliation(s)
- Luis Pianciola
- Laboratorio Central, Subsecretaría de Salud de Neuquén, Gregorio Martínez 65, Neuquén 8300, Argentina.
| | - Marta Rivas
- Servicio Fisiopatogenia, INEI-ANLIS "Carlos G. Malbrán", Av. Vélez Sarsfield 563, Buenos Aires 1281, Argentina.
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46
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Tanaro JD, Pianciola LA, D'Astek BA, Piaggio MC, Mazzeo ML, Zolezzi G, Rivas M. Virulence profile of Escherichia coli O157 strains isolated from surface water in cattle breeding areas. Lett Appl Microbiol 2018; 66:484-490. [PMID: 29500840 DOI: 10.1111/lam.12873] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Revised: 02/12/2018] [Accepted: 02/24/2018] [Indexed: 01/31/2023]
Abstract
Shiga toxin-producing Escherichia coli (STEC) O157:H7 is a worldwide concern. Cattle are their main reservoir and may contaminate watercourses through manure. We characterized a collection of 38 STEC O157:H7 strains isolated from surface water in feedlots areas (puddles inside pens formed after the rainfall or by spill around drinking troughs, and small water courses and lagoons, formed by runoff). Nineteen (50·0%) strains harboured stx2a /stx2c genes, 18 (47·4%) stx2c and one stx1a /stx2c . All strains harboured eae, ehxA, rfbO157 and fliCH7 genes, and the putative virulence determinants ECSP_0242, ECSP_2687 and ECSP_3620. All isolates tested as Lineage I/II by lineage-specific polymorphism assay-6. Nineteen (50%) belonged to the high virulent clade 8. The q21 allele was found in all strains and q933 /q21 alleles in 17 (44·7%). By XbaI-pulsed-field gel electrophoresis, 29 strains were grouped into seven clusters. Four clusters grouped isolates from distant places separated by 150-250 km. This may be related to vectors, like birds, involved in their spread. Otherwise, three clusters contained isolates recovered at same places with intervals of 1-9 months. This could be explained by the high environmental persistence of STEC O157:H7. These strains recovered from surface water showed similar genotypes to those found in the bovine reservoir and in human diseases, and could be linked to the high incidence of haemolytic uremic syndrome in Argentina. SIGNIFICANCE AND IMPACT OF THE STUDY The challenge for the growing global demand for food is to find sustained production strategies without collateral effects. Intensive livestock operations generate large volumes of manure that can contaminate a finite resource, the water. This study shows how water contaminated by confined feeding operations can transport dangerous pathogens and warns to pay more attention to control and sanitation systems to prevent this type of pollution.
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Affiliation(s)
- J D Tanaro
- Cátedra de Microbiología, Facultad De Bromatología, Universidad Nacional de Entre Ríos, Gualeguaychú, Argentina
| | - L A Pianciola
- Laboratorio Central, Subsecretaría de Salud de Neuquén, Neuquén, Argentina
| | - B A D'Astek
- Servicio Fisiopatogenia, Departamento Bacteriología, INEI-ANLIS "Dr. Carlos G. Malbrán", Buenos Aires, Argentina
| | - M C Piaggio
- Cátedra de Microbiología, Facultad De Bromatología, Universidad Nacional de Entre Ríos, Gualeguaychú, Argentina
| | - M L Mazzeo
- Laboratorio Central, Subsecretaría de Salud de Neuquén, Neuquén, Argentina
| | - G Zolezzi
- Servicio Fisiopatogenia, Departamento Bacteriología, INEI-ANLIS "Dr. Carlos G. Malbrán", Buenos Aires, Argentina
| | - M Rivas
- Servicio Fisiopatogenia, Departamento Bacteriología, INEI-ANLIS "Dr. Carlos G. Malbrán", Buenos Aires, Argentina
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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: 1.1] [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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Enterohemorrhagic Escherichia coli O157 subclade 8b strains in Chiba Prefecture, Japan, produced larger amounts of Shiga toxin 2 than strains in subclade 8a and other clades. PLoS One 2018; 13:e0191834. [PMID: 29381715 PMCID: PMC5790261 DOI: 10.1371/journal.pone.0191834] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Accepted: 01/11/2018] [Indexed: 11/19/2022] Open
Abstract
Enterohemorrhagic Escherichia coli O157 (O157) strains can be classified into clades (one of several phylogenetic groups) by single nucleotide polymorphisms (SNPs): these are clade 1, clade 2, clade 3, descendant and ancestral clades 4/5, clade 6, clade 7, clade 8, clade 9, and clade 12. Some recent studies showed that some O157 strains in clade 8 produced a larger amount of Shiga toxin (Stx) 2 than other strains. In this study, 1121 epidemiologically unlinked strains of O157 isolated in Chiba Prefecture, Japan were classified into clades during 1996–2014. Clade 8 strains were further classified into subclade 8a (67 strains) and subclade 8b (48 strains) using SNP analysis. In the absence of mitomycin C (MMC), subclade 8a strains in this study produced significantly greater amounts of Stx2 than subclade 8b strains. However, in the presence of MMC, the levels of Stx2 production in subclade 8b strains were significantly greater than subclade 8a strains. On the other hand, a recent study reported that the Stx2 production level in O157 strains was determined mainly by the subtypes of Stx2a phage (ϕStx2_α, β, γ, δ, ε, and ζ). Using O157 strains in this study, the Stx2a phages were classified into these subtypes. In this study, all strains of subclades 8a and 8b carried ϕStx2a_γ and ϕStx2a_δ, respectively. Some strains in clade 6 also carried ϕStx2a_δ. In the presence of MMC, subclade 8b strains produced significantly greater amounts of Stx2 than clade 6 strains carrying ϕStx2_δ. In this study, we propose that Stx2 production in subclade 8b strains in the presence of MMC might be enhanced due to genetic factors other than ϕStx2_δ.
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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: 2.7] [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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Mitsunaka S, Sudo N, Sekine Y. Lysogenisation of Shiga toxin-encoding bacteriophage represses cell motility. J GEN APPL MICROBIOL 2017; 64:34-41. [PMID: 29225287 DOI: 10.2323/jgam.2017.05.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Bacteriophages are genetic elements that play key roles in the evolution and diversification of bacterial genomes. The Shiga toxin (Stx)-encoding phage plays an important role in the horizontal transfer of the stx gene. However, the influence of the Stx phage integration on the physiological properties and gene expression pattern of the host have not been clearly resolved. In this study, we constructed the Sp5 lysogen through lysogenisation of E. coli K-12 by Sp5, an Stx2 phage in enterohaemorrhagic E. coli (EHEC) O157:H7 Sakai, and examined the effect of the resulting lysogen on cell motility under various growth conditions. Sp5 lysogenisation decreased cell motility and the expression of fliC, which encodes flagellin, under anaerobic conditions at 37°C. Sp5 also lowered the expression of fliA, which encodes the FliA-sigma factor responsible for the transcription of fliC, and flhD, which facilitates the expression of fliA. Sp5 lysogenisation reduced the amount of FlhD and FlhC expressed from the araBAD promoter, suggesting that one or more genes present in Sp5 represses flhDC at the post-transcriptional level. Flagellin is highly antigenic and triggers an immune response in the host. Thus, Sp5 might enhance its viability by repressing the expression of the flagellar regulon to circumvent the immune response of host cells.
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Affiliation(s)
| | - Naoki Sudo
- Department of Life Science, College of Science, Rikkyo University
| | - Yasuhiko Sekine
- Department of Life Science, College of Science, Rikkyo University
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