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Shuster M, Lyu Z, Augenstreich J, Mathur S, Ganesh A, Ling J, Briken V. Salmonella Typhimurium infection inhibits macrophage IFNβ signaling in a TLR4-dependent manner. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.05.583530. [PMID: 38496427 PMCID: PMC10942315 DOI: 10.1101/2024.03.05.583530] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/19/2024]
Abstract
Type I Interferons (IFNs) generally have a protective role during viral infections, but their function during bacterial infections is dependent on the bacterial species. Legionella pneumophila, Shigella sonnei and Mycobacterium tuberculosis can inhibit type I IFN signaling. Here we examined the role of type I IFN, specifically IFNβ, in the context of Salmonella enterica serovar Typhimurium (STm) macrophage infections and the capacity of STm to inhibit type I IFN signaling. We demonstrate that IFNβ has no effect on the intracellular growth of STm in infected bone marrow derived macrophages (BMDMs) derived from C57BL/6 mice. STm infection inhibits IFNβ signaling but not IFNγ signaling in a murine macrophage cell line. We show that this inhibition is independent of the type III and type VI secretion systems expressed by STm and is also independent of bacterial phagocytosis. The inhibition is Toll-like receptor 4 (TLR4)-dependent as the TLR4 ligand, lipopolysaccharide (LPS), alone is sufficient to inhibit IFNβ-mediated signaling and STm-infected, TLR4-deficient BMDMs do not exhibit inhibited IFNβ signaling. In summary, we show that macrophages exposed to STm have reduced IFNβ signaling via crosstalk with TLR4 signaling, and that IFNβ signaling does not affect cell autonomous host defense against STm.
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Affiliation(s)
- Michael Shuster
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD, USA
| | - Zhihui Lyu
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD, USA
| | - Jacques Augenstreich
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD, USA
| | - Shrestha Mathur
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD, USA
| | - Akshaya Ganesh
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD, USA
| | - Jiqiang Ling
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD, USA
| | - Volker Briken
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD, USA
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2
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Chatterjee R, Chowdhury AR, Mukherjee D, Chakravortty D. From Eberthella typhi to Salmonella Typhi: The Fascinating Journey of the Virulence and Pathogenicity of Salmonella Typhi. ACS OMEGA 2023; 8:25674-25697. [PMID: 37521659 PMCID: PMC10373206 DOI: 10.1021/acsomega.3c02386] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/09/2023] [Accepted: 06/30/2023] [Indexed: 08/01/2023]
Abstract
Salmonella Typhi (S. Typhi), the invasive typhoidal serovar of Salmonella enterica that causes typhoid fever in humans, is a severe threat to global health. It is one of the major causes of high morbidity and mortality in developing countries. According to recent WHO estimates, approximately 11-21 million typhoid fever illnesses occur annually worldwide, accounting for 0.12-0.16 million deaths. Salmonella infection can spread to healthy individuals by the consumption of contaminated food and water. Typhoid fever in humans sometimes is accompanied by several other critical extraintestinal complications related to the central nervous system, cardiovascular system, pulmonary system, and hepatobiliary system. Salmonella Pathogenicity Island-1 and Salmonella Pathogenicity Island-2 are the two genomic segments containing genes encoding virulent factors that regulate its invasion and systemic pathogenesis. This Review aims to shed light on a comparative analysis of the virulence and pathogenesis of the typhoidal and nontyphoidal serovars of S. enterica.
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Affiliation(s)
- Ritika Chatterjee
- Department
of Microbiology and Cell Biology, Division of Biological Sciences, Indian Institute of Science, Bangalore, Karnataka 560012, India
| | - Atish Roy Chowdhury
- Department
of Microbiology and Cell Biology, Division of Biological Sciences, Indian Institute of Science, Bangalore, Karnataka 560012, India
| | - Debapriya Mukherjee
- Department
of Microbiology and Cell Biology, Division of Biological Sciences, Indian Institute of Science, Bangalore, Karnataka 560012, India
| | - Dipshikha Chakravortty
- Department
of Microbiology and Cell Biology, Division of Biological Sciences, Indian Institute of Science, Bangalore, Karnataka 560012, India
- Centre
for Biosystems Science and Engineering, Indian Institute of Science, Bangalore, Karnataka 560012, India
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3
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Singh RP, Kumari K. Bacterial type VI secretion system (T6SS): an evolved molecular weapon with diverse functionality. Biotechnol Lett 2023; 45:309-331. [PMID: 36683130 DOI: 10.1007/s10529-023-03354-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Revised: 12/14/2022] [Accepted: 01/05/2023] [Indexed: 01/24/2023]
Abstract
Bacterial secretion systems are nanomolecular complexes that release a diverse set of virulence factors/or proteins into its surrounding or translocate to their target host cells. Among these systems, type VI secretion system 'T6SS' is a recently discovered molecular secretion system which is widely distributed in Gram-negative (-ve) bacteria, and shares structural similarity with the puncturing device of bacteriophages. The presence of T6SS is an advantage to many bacteria as it delivers toxins to its neighbour pathogens for competitive survival, and also translocates protein effectors to the host cells, leading to disruption of lipid membranes, cell walls, and cytoskeletons etc. Recent studies have characterized both anti-prokaryotic and anti-eukaryotic effectors, where T6SS is involved in diverse cellular functions including favouring colonization, enhancing the survival, adhesive modifications, internalization, and evasion of the immune system. With the evolution of advanced genomics and proteomics tools, there has been an increase in the number of characterized T6SS effector arsenals and also more clear information about the adaptive significance of this complex system. The functions of T6SS are generally regulated at the transcription, post-transcription and post-translational levels through diverse mechanisms. In the present review, we aimed to provide information about the distribution of T6SS in diverse bacteria, any structural similarity/or dissimilarity, effectors proteins, functional significance, and regulatory mechanisms. We also tried to provide information about the diverse roles played by T6SS in its natural environments and hosts, and further any changes in the microbiome.
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Affiliation(s)
- Rajnish Prakash Singh
- Department of Bioengineering and Biotechnology, Birla Institute of Technology, Mesra, Ranchi, Jharkhand, 835215, India.
| | - Kiran Kumari
- Department of Bioengineering and Biotechnology, Birla Institute of Technology, Mesra, Ranchi, Jharkhand, 835215, India
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4
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Elucidation of a complete mechanical signaling and virulence activation pathway in enterohemorrhagic Escherichia coli. Cell Rep 2022; 39:110614. [PMID: 35385749 DOI: 10.1016/j.celrep.2022.110614] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Revised: 12/09/2021] [Accepted: 03/13/2022] [Indexed: 12/23/2022] Open
Abstract
Enterohemorrhagic Escherichia coli (EHEC) O157:H7 is an important extracellular human pathogen. The initial adherence of EHEC to host cells is a major cue for transcriptional induction of the locus of enterocyte effacement (LEE) genes to promote colonization and pathogenesis, but the mechanism through which this adherence is sensed and the LEE is induced remains largely elusive. Here, we report a complete signal transduction pathway for this virulence activation process. In this pathway, the outer-membrane lipoprotein NlpE senses a mechanical cue generated from initial host adherence and activates the BaeSR two-component regulatory system; the response regulator BaeR then directly activates the expression of airA located on O-island-134 and encoding a LEE transcriptional activator. Disruption of this pathway severely attenuates EHEC O157:H7 virulence both in vitro and in vivo. This study provides further insights into the evolution of EHEC pathogenesis and the host-pathogen interaction.
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Amaya FA, Blondel CJ, Barros-Infante MF, Rivera D, Moreno-Switt AI, Santiviago CA, Pezoa D. Identification of Type VI Secretion Systems Effector Proteins That Contribute to Interbacterial Competition in Salmonella Dublin. Front Microbiol 2022; 13:811932. [PMID: 35222335 PMCID: PMC8867033 DOI: 10.3389/fmicb.2022.811932] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Accepted: 01/04/2022] [Indexed: 12/12/2022] Open
Abstract
The Type VI Secretion System (T6SS) is a multiprotein device that has emerged as an important fitness and virulence factor for many Gram-negative bacteria through the injection of effector proteins into prokaryotic or eukaryotic cells via a contractile mechanism. While some effector proteins specifically target bacterial or eukaryotic cells, others can target both types of cells (trans-kingdom effectors). In Salmonella, five T6SS gene clusters have been identified within pathogenicity islands SPI-6, SPI-19, SPI-20, SPI-21, and SPI-22, which are differentially distributed among serotypes. Salmonella enterica serotype Dublin (S. Dublin) is a cattle-adapted pathogen that harbors both T6SSSPI-6 and T6SSSPI-19. Interestingly, while both systems have been linked to virulence and host colonization in S. Dublin, an antibacterial activity has not been detected for T6SSSPI-6 in this serotype. In addition, there is limited information regarding the repertoire of effector proteins encoded within T6SSSPI-6 and T6SSSPI-19 gene clusters in S. Dublin. In the present study, we demonstrate that T6SSSPI-6 and T6SSSPI-19 of S. Dublin CT_02021853 contribute to interbacterial competition. Bioinformatic and comparative genomic analyses allowed us to identify genes encoding three candidate antibacterial effectors located within SPI-6 and two candidate effectors located within SPI-19. Each antibacterial effector gene is located upstream of a gene encoding a hypothetic immunity protein, thus conforming an effector/immunity (E/I) module. Of note, the genes encoding these effectors and immunity proteins are widely distributed in Salmonella genomes, suggesting a relevant role in interbacterial competition and virulence. Finally, we demonstrate that E/I modules SED_RS01930/SED_RS01935 (encoded in SPI-6), SED_RS06235/SED_RS06230, and SED_RS06335/SED_RS06340 (both encoded in SPI-19) contribute to interbacterial competition in S. Dublin CT_02021853.
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Affiliation(s)
- Fernando A. Amaya
- Laboratorio de Microbiología, Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santiago, Chile
| | - Carlos J. Blondel
- Instituto de Ciencias Biomédicas, Facultad de Medicina y Facultad de Ciencias de la Vida, Universidad Andrés Bello, Santiago, Chile
| | | | - Dácil Rivera
- Escuela de Medicina Veterinaria, Facultad de Ciencias de la Vida, Universidad Andrés Bello, Santiago, Chile
| | - Andrea I. Moreno-Switt
- Escuela de Medicina Veterinaria, Facultad de Agronomía e Ingeniería Forestal, Facultad de Ciencias Biológicas y Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
- Millennium Initiative on Collaborative Research on Bacterial Resistance (MICROB-R), Santiago, Chile
| | - Carlos A. Santiviago
- Laboratorio de Microbiología, Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santiago, Chile
- *Correspondence: Carlos A. Santiviago, David Pezoa,
| | - David Pezoa
- Escuela de Medicina Veterinaria, Facultad de Ciencias, Universidad Mayor, Santiago, Chile
- *Correspondence: Carlos A. Santiviago, David Pezoa,
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6
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The cost of bacterial predation via type VI secretion system leads to predator extinction under environmental stress. iScience 2021; 24:103507. [PMID: 34934926 PMCID: PMC8654991 DOI: 10.1016/j.isci.2021.103507] [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: 07/14/2021] [Revised: 10/21/2021] [Accepted: 11/22/2021] [Indexed: 11/13/2022] Open
Abstract
As a common gut pathogen, Campylobacter jejuni (C. jejuni) harbors the Type VI Secretion System (T6SS) that injects toxic effectors into neighboring cells, modulating microbial competitions in the harsh gut environment. Using bile salt as a natural stressor and T6SS-positive C. jejuni as a predator, we show that T6SS activity could entail a cost during bacterial predation under environmental stress. Our data suggest bile salt influx and subsequent DNA damage due to the prey-driven activation of the T6SS. We further combined experiments and mathematical modeling to explore how the stress-induced “predation cost” determines ecological outcomes. Consistent with a population-dynamics model, we found predator extinction above a critical bile salt concentration and prey-predator coexistence below this level. Moreover, we utilized the predation cost as an effective strategy facilitating host defense against C. jejuni infection. Together, we elucidate how predator dominance versus extinction emerges from the interplay between environmental stress and the T6SS machinery. Campylobacter jejuni uses Type VI secretion system (T6SS) to kill prey bacteria Under bile salt stress, activated T6SS may promote bile salt uptake and DNA damage T6SS-dependent predation by C. jejuni thus entails a “predation cost” under stress The predation cost leads to predator extinction and host defense against C. jejuni
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7
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Swietnicki W. Secretory System Components as Potential Prophylactic Targets for Bacterial Pathogens. Biomolecules 2021; 11:892. [PMID: 34203937 PMCID: PMC8232601 DOI: 10.3390/biom11060892] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2021] [Revised: 06/13/2021] [Accepted: 06/14/2021] [Indexed: 01/18/2023] Open
Abstract
Bacterial secretory systems are essential for virulence in human pathogens. The systems have become a target of alternative antibacterial strategies based on small molecules and antibodies. Strategies to use components of the systems to design prophylactics have been less publicized despite vaccines being the preferred solution to dealing with bacterial infections. In the current review, strategies to design vaccines against selected pathogens are presented and connected to the biology of the system. The examples are given for Y. pestis, S. enterica, B. anthracis, S. flexneri, and other human pathogens, and discussed in terms of effectiveness and long-term protection.
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Affiliation(s)
- Wieslaw Swietnicki
- Department of Immunology of Infectious Diseases, Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, ul. R. Weigla 12, 53-114 Wroclaw, Poland
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8
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The SPI-19 encoded T6SS is required for Salmonella Pullorum survival within avian macrophages and initial colonization in chicken dependent on inhibition of host immune response. Vet Microbiol 2020; 250:108867. [PMID: 33010573 DOI: 10.1016/j.vetmic.2020.108867] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Accepted: 09/22/2020] [Indexed: 12/12/2022]
Abstract
SalmonellaPathogenicity Island 19 (SPI-19) encoded type VI secretion system (T6SS) is a virulence factor present in few serotypes of S. enterica, including S. Dublin, S. Gallinarum and S. Pullorum. Comparative genomic sequence analysis revealed that the gene clusters of SPI-19 showed high homology to T6SS2 locus from avian pathogenic Escherichia coli, implying the similar T6SS locus is potentially related to the host adaption of both pathogens. Deletion of SPI-19 in S. Pullorum caused the dramatically decreased invasion into chicken LMH epithelial cells and HD-11 macrophages, and affected survival of Salmonella within both cells. In addition, deletion of SPI-19 caused the decreased colonization of S. Pullorum in chicken liver, spleen, ileum, and cecum at the initial infection stage, and induced rapid bacterial clearance. However, the SPI-19/T6SS had no effect on bacterial killing activity and induction of cytotoxicity to HD-11 macrophages. Further analysis demonstrated SPI-19/T6SS was involved in mediating the inhibition of host Th1 and Th2 immune responses, resulting in persistent colonization of S. Pullorum in hosts.
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9
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Bao H, Wang S, Zhao JH, Liu SL. Salmonella secretion systems: Differential roles in pathogen-host interactions. Microbiol Res 2020; 241:126591. [PMID: 32932132 DOI: 10.1016/j.micres.2020.126591] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Revised: 08/24/2020] [Accepted: 08/29/2020] [Indexed: 12/26/2022]
Abstract
The bacterial genus Salmonella includes a large group of food-borne pathogens that cause a variety of gastrointestinal or systemic diseases in hosts. Salmonella use several secretion devices to inject various effectors targeting eukaryotic hosts, or bacteria. In the past few years, considerable progress has been made towards understanding the structural features and molecular mechanisms of the secretion systems of Salmonella, particularly regarding their roles in host-pathogen interactions. In this review, we summarize the current advances about the main characteristics of the Salmonella secretion systems. Clarifying the roles of the secretion systems in the process of infecting various hosts will broaden our understanding of the importance of microbial interactions in maintaining human health and will provide information for developing novel therapeutic approaches.
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Affiliation(s)
- Hongxia Bao
- Genomics Research Center, College of Pharmacy, Harbin Medical University, Harbin, China; HMU-UCCSM Centre for Infection and Genomics, Harbin Medical University, Harbin, China; Translational Medicine Research and Cooperation Center of Northern China, Heilongjiang Academy of Medical Sciences, Harbin, China.
| | - Shuang Wang
- Department of Biopharmaceutical Sciences (State-Province Key Laboratories of Biomedicine-Pharmaceutics of China), College of Pharmacy, Harbin Medical University, Harbin, China
| | - Jian-Hua Zhao
- Genomics Research Center, College of Pharmacy, Harbin Medical University, Harbin, China; HMU-UCCSM Centre for Infection and Genomics, Harbin Medical University, Harbin, China; Translational Medicine Research and Cooperation Center of Northern China, Heilongjiang Academy of Medical Sciences, Harbin, China
| | - Shu-Lin Liu
- Genomics Research Center, College of Pharmacy, Harbin Medical University, Harbin, China; HMU-UCCSM Centre for Infection and Genomics, Harbin Medical University, Harbin, China; Translational Medicine Research and Cooperation Center of Northern China, Heilongjiang Academy of Medical Sciences, Harbin, China; Department of Microbiology, Immunology and Infectious Diseases, University of Calgary, Calgary, Canada.
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10
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Barretto LAF, Fowler CC. Identification of A Putative T6SS Immunity Islet in Salmonella Typhi. Pathogens 2020; 9:pathogens9070559. [PMID: 32664482 PMCID: PMC7400221 DOI: 10.3390/pathogens9070559] [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: 06/19/2020] [Revised: 07/05/2020] [Accepted: 07/06/2020] [Indexed: 12/19/2022] Open
Abstract
Typhoid fever is a major global health problem and is the result of systemic infections caused by the human-adapted bacterial pathogen Salmonella enterica serovar Typhi (S. Typhi). The pathology underlying S. Typhi infections significantly differ from infections caused by broad host range serovars of the same species, which are a common cause of gastroenteritis. Accordingly, identifying S. Typhi genetic factors that impart functionality absent from broad host range serovars offers insights into its unique biology. Here, we used an in-silico approach to explore the function of an uncharacterized 14-gene S. Typhi genomic islet. Our results indicated that this islet was specific to the S. enterica species, where it was encoded by the Typhi and Paratyphi A serovars, but was generally absent from non-typhoidal serovars. Evidence was gathered using comparative genomics and sequence analysis tools, and indicated that this islet was comprised of Type VI secretion system (T6SS) and contact-dependent growth inhibition (CDI) genes, the majority of which appeared to encode orphan immunity proteins that protected against the activities of effectors and toxins absent from the S. Typhi genome. We herein propose that this islet represents an immune system that protects S. Typhi against competing bacteria within the human gut.
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The Ferric Uptake Regulator Represses Type VI Secretion System Function by Binding Directly to the clpV Promoter in Salmonella enterica Serovar Typhimurium. Infect Immun 2019; 87:IAI.00562-19. [PMID: 31383745 DOI: 10.1128/iai.00562-19] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Accepted: 07/25/2019] [Indexed: 12/16/2022] Open
Abstract
Type VI secretion systems (T6SSs) are highly conserved and complex protein secretion systems that deliver effector proteins into eukaryotic hosts or other bacteria. T6SSs are regulated precisely by a variety of regulatory systems, which enables bacteria to adapt to varied environments. A T6SS within Salmonella pathogenicity island 6 (SPI-6) is activated during infection, and it contributes to the pathogenesis, as well as interbacterial competition, of Salmonella enterica serovar Typhimurium (S. Typhimurium). However, the regulation of the SPI-6 T6SS in S. Typhimurium is not well understood. In this study, we found that the SPI-6 T6SS core gene clpV was significantly upregulated in response to the iron-depleted condition and during infection. The global ferric uptake regulator (Fur) was shown to repress the clpV expression in the iron-replete medium. Moreover, electrophoretic mobility shift and DNase I footprinting assays revealed that Fur binds directly to the clpV promoter region at multiple sites spanning the transcriptional start site. We also observed that the relieving of Fur-mediated repression on clpV contributed to the interbacterial competition activity and pathogenicity of S. Typhimurium. These findings provide insights into the direct regulation of Fur in the expression and functional activity of SPI-6 T6SS in S. Typhimurium and thus help to elucidate the mechanisms of bacterial adaptability and virulence.
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12
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Chen C, Yang X, Shen X. Confirmed and Potential Roles of Bacterial T6SSs in the Intestinal Ecosystem. Front Microbiol 2019; 10:1484. [PMID: 31316495 PMCID: PMC6611333 DOI: 10.3389/fmicb.2019.01484] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Accepted: 06/14/2019] [Indexed: 12/25/2022] Open
Abstract
The contact-dependent type VI secretion system (T6SS) in diverse microbes plays crucial roles in both inter-bacterial and bacteria-host interactions. As numerous microorganisms inhabit the intestinal ecosystem at a high density, it is necessary to consider the functions of T6SS in intestinal bacteria. In this mini-review, we discuss T6SS-dependent functions in intestinal microbes, including commensal microbes and enteric pathogens, and list experimentally verified species of intestinal bacteria containing T6SS clusters. Several seminal studies have shown that T6SS plays crucial antibacterial roles in colonization resistance, niche occupancy, activation of host innate immune responses, and modulation of host intestinal mechanics. Some potential roles of T6SS in the intestinal ecosystem, such as targeting of single cell eukaryotic competitors, competition for micronutrients, and stress resistance are also discussed. Considering the distinct activities of T6SS in diverse bacteria residing in the intestine, we suggest that T6SS research in intestinal microbes may be beneficial for the future development of new medicines and clinical treatments.
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Affiliation(s)
- Can Chen
- Institute of Food and Drug Inspection, College of Life Science and Agronomy, Zhoukou Normal University, Zhoukou, China
| | - Xiaobing Yang
- State Key Laboratory of Crop Stress Biology for Arid Areas, Shaanxi Key Laboratory of Agricultural and Environmental Microbiology, College of Life Sciences, Northwest A&F University, Yangling, China
| | - Xihui Shen
- State Key Laboratory of Crop Stress Biology for Arid Areas, Shaanxi Key Laboratory of Agricultural and Environmental Microbiology, College of Life Sciences, Northwest A&F University, Yangling, China
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13
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Yang X, Pan J, Wang Y, Shen X. Type VI Secretion Systems Present New Insights on Pathogenic Yersinia. Front Cell Infect Microbiol 2018; 8:260. [PMID: 30109217 PMCID: PMC6079546 DOI: 10.3389/fcimb.2018.00260] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Accepted: 07/13/2018] [Indexed: 12/22/2022] Open
Abstract
The type VI secretion system (T6SS) is a versatile secretion system widely distributed in Gram-negative bacteria that delivers multiple effector proteins into either prokaryotic or eukaryotic cells, or into the extracellular milieu. T6SS participates in various physiological processes including bacterial competition, host infection, and stress response. Three pathogenic Yersinia species, namely Yersinia pestis, Yersinia pseudotuberculosis, and Yersinia enterocolitica, possess different copies of T6SSs with distinct biological functions. This review summarizes the pathogenic, antibacterial, and stress-resistant roles of T6SS in Yersinia and the ion-transporting ability in Y. pseudotuberculosis. In addition, the T6SS-related effectors and regulators identified in Yersinia are discussed.
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Affiliation(s)
- Xiaobing Yang
- State Key Laboratory of Crop Stress Biology for Arid Areas, College of Life Sciences, Northwest A&F University, Yangling, China.,Shaanxi Key Laboratory of Agricultural and Environmental Microbiology, College of Life Sciences, Northwest A&F University, Yangling, China
| | - Junfeng Pan
- Shaanxi Key Laboratory of Agricultural and Environmental Microbiology, College of Life Sciences, Northwest A&F University, Yangling, China
| | - Yao Wang
- Shaanxi Key Laboratory of Agricultural and Environmental Microbiology, College of Life Sciences, Northwest A&F University, Yangling, China
| | - Xihui Shen
- State Key Laboratory of Crop Stress Biology for Arid Areas, College of Life Sciences, Northwest A&F University, Yangling, China.,Shaanxi Key Laboratory of Agricultural and Environmental Microbiology, College of Life Sciences, Northwest A&F University, Yangling, China
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14
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Effector⁻Immunity Pairs Provide the T6SS Nanomachine its Offensive and Defensive Capabilities. Molecules 2018; 23:molecules23051009. [PMID: 29701633 PMCID: PMC6099711 DOI: 10.3390/molecules23051009] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Revised: 04/13/2018] [Accepted: 04/23/2018] [Indexed: 01/23/2023] Open
Abstract
Type VI protein secretion systems (T6SSs) are specialized transport apparatus which can target both eukaryotic and prokaryotic cells and play key roles in host⁻pathogen⁻microbiota interactions. Therefore, T6SSs have attracted much attention as a research topic during the past ten years. In this review, we particularly summarized the T6SS antibacterial function, which involves an interesting offensive and defensive mechanism of the effector⁻immunity (E⁻I) pairs. The three main categories of effectors that target the cell wall, membranes, and nucleic acids during bacterial interaction, along with their corresponding immunity proteins are presented. We also discuss structural analyses of several effectors and E⁻I pairs, which explain the offensive and defensive mechanisms underpinning T6SS function during bacterial competition for niche-space, as well as the bioinformatics, proteomics, and protein⁻protein interaction (PPI) methods used to identify and characterize T6SS mediated E⁻I pairs. Additionally, we described PPI methods for verifying E⁻I pairs.
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15
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Chourashi R, Das S, Dhar D, Okamoto K, Mukhopadhyay AK, Chatterjee NS. Chitin-induced T6SS in Vibrio cholerae is dependent on ChiS activation. MICROBIOLOGY-SGM 2018; 164:751-763. [PMID: 29633936 DOI: 10.1099/mic.0.000656] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Vibrio cholerae regularly colonizes the chitinous exoskeleton of crustacean shells in the aquatic region. The type 6 secretion system (T6SS) in V. cholerae is an interbacterial killing device. This system is thought to provide a competitive advantage to V. cholerae in a polymicrobial community of the aquatic region under nutrient-poor conditions. V. cholerae chitin sensing is known to be initiated by the activation of a two-component sensor histidine kinase ChiS in the presence of GlcNAc2 (N,N'-diacetylchitobiose) residues generated by the action of chitinases on chitin. It is known that T6SS in V. cholerae is generally induced by chitin. However, the effect of ChiS activation on T6SS is unknown. Here, we found that ChiS inactivation resulted in impaired bacterial killing and reduced expression of T6SS genes. Active ChiS positively affected T6SS-mediated natural transformation in V. cholerae. ChiS depletion or inactivation also resulted in reduced colonization on insoluble chitin surfaces. Therefore, we have shown that V. cholerae colonization on chitinous surfaces activates ChiS, which promotes T6SS-dependent bacterial killing and horizontal gene transfer. We also highlight the importance of chitinases in T6SS upregulation.
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Affiliation(s)
- Rhishita Chourashi
- Division of Biochemistry, National Institute of Cholera and Enteric Diseases, Kolkata 700010, India
| | - Suman Das
- Division of Biochemistry, National Institute of Cholera and Enteric Diseases, Kolkata 700010, India
| | - Debarpan Dhar
- Division of Clinical Medicine, National Institute of Cholera and Enteric Diseases, Kolkata 700010, India
| | - Keinosuke Okamoto
- Collaborative Research Center of Okayama University for Infectious Diseases at NICED, Kolkata, India
| | - Asish K Mukhopadhyay
- Division of Bacteriology, National Institute of Cholera and Enteric Diseases, Kolkata 700010, India
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Abstract
The type VI secretion system (T6SS) is a multiprotein complex widespread in Proteobacteria and dedicated to the delivery of toxins into both prokaryotic and eukaryotic cells. It thus participates in interbacterial competition as well as pathogenesis. The T6SS is a contractile weapon, related to the injection apparatus of contractile tailed bacteriophages. Basically, it assembles an inner tube wrapped by a sheath-like structure and anchored to the cell envelope via a membrane complex. The energy released by the contraction of the sheath propels the inner tube through the membrane channel and toward the target cell. Although the assembly and the mechanism of action are conserved across species, the repertoire of secreted toxins and the diversity of the regulatory mechanisms and of target cells make the T6SS a highly versatile secretion system. The T6SS is particularly represented in Escherichia coli pathotypes and Salmonella serotypes. In this review we summarize the current knowledge regarding the prevalence, the assembly, the regulation, and the roles of the T6SS in E. coli, Salmonella, and related species.
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Miao M, Cao W, Wang H, Yan J, Wang M, Zheng Y, Xie X, Zhang X, Zhang H, Du H. ramR is not involved in the regulation of ramA associated antibiotic resistance in Salmonella enterica serovar Typhi. Microb Pathog 2017; 111:198-202. [DOI: 10.1016/j.micpath.2017.08.052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2017] [Revised: 08/20/2017] [Accepted: 08/30/2017] [Indexed: 11/16/2022]
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18
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Hume PJ, Singh V, Davidson AC, Koronakis V. Swiss Army Pathogen: The Salmonella Entry Toolkit. Front Cell Infect Microbiol 2017; 7:348. [PMID: 28848711 PMCID: PMC5552672 DOI: 10.3389/fcimb.2017.00348] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Accepted: 07/21/2017] [Indexed: 02/04/2023] Open
Abstract
Salmonella causes disease in humans and animals ranging from mild self-limiting gastroenteritis to potentially life-threatening typhoid fever. Salmonellosis remains a considerable cause of morbidity and mortality globally, and hence imposes a huge socio-economic burden worldwide. A key property of all pathogenic Salmonella strains is the ability to invade non-phagocytic host cells. The major determinant of this invasiveness is a Type 3 Secretion System (T3SS), a molecular syringe that injects virulence effector proteins directly into target host cells. These effectors cooperatively manipulate multiple host cell signaling pathways to drive pathogen internalization. Salmonella does not only rely on these injected effectors, but also uses several other T3SS-independent mechanisms to gain entry into host cells. This review summarizes our current understanding of the methods used by Salmonella for cell invasion, with a focus on the host signaling networks that must be coordinately exploited for the pathogen to achieve its goal.
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Affiliation(s)
- Peter J Hume
- Department of Pathology, University of CambridgeCambridge, United Kingdom
| | - Vikash Singh
- Department of Pathology, University of CambridgeCambridge, United Kingdom
| | - Anthony C Davidson
- Department of Pathology, University of CambridgeCambridge, United Kingdom
| | - Vassilis Koronakis
- Department of Pathology, University of CambridgeCambridge, United Kingdom
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19
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Rasmussen-Ivey CR, Hossain MJ, Odom SE, Terhune JS, Hemstreet WG, Shoemaker CA, Zhang D, Xu DH, Griffin MJ, Liu YJ, Figueras MJ, Santos SR, Newton JC, Liles MR. Classification of a Hypervirulent Aeromonas hydrophila Pathotype Responsible for Epidemic Outbreaks in Warm-Water Fishes. Front Microbiol 2016; 7:1615. [PMID: 27803692 PMCID: PMC5067525 DOI: 10.3389/fmicb.2016.01615] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Accepted: 09/27/2016] [Indexed: 11/24/2022] Open
Abstract
Lineages of hypervirulent Aeromonas hydrophila (vAh) are the cause of persistent outbreaks of motile Aeromonas septicemia in warm-water fishes worldwide. Over the last decade, this virulent lineage of A. hydrophila has resulted in annual losses of millions of tons of farmed carp and catfish in the People's Republic of China and the United States (US). Multiple lines of evidence indicate US catfish and Asian carp isolates of A. hydrophila affiliated with sequence type 251 (ST251) share a recent common ancestor. To address the genomic context for the putative intercontinental transfer and subsequent geographic spread of this pathogen, we conducted a core genome phylogenetic analysis on 61 Aeromonas spp. genomes, of which 40 were affiliated with A. hydrophila, with 26 identified as epidemic strains. Phylogenetic analyses indicate all ST251 strains form a coherent lineage affiliated with A. hydrophila. Within this lineage, conserved genetic loci unique to A. hydrophila were identified, with some genes present in consistently higher copy numbers than in non-epidemic A. hydrophila isolates. In addition, results from analyses of representative ST251 isolates support the conclusion that multiple lineages are present within US vAh isolated from Mississippi, whereas vAh isolated from Alabama appear clonal. This is the first report of genomic heterogeneity within US vAh isolates, with some Mississippi isolates showing closer affiliation with the Asian grass carp isolate ZC1 than other vAh isolated in the US. To evaluate the biological significance of the identified heterogeneity, comparative disease challenges were conducted with representatives of different vAh genotypes. These studies revealed that isolate ZC1 yielded significantly lower mortality in channel catfish, relative to Alabama and Mississippi vAh isolates. Like other Asian vAh isolates, the ZC1 lineage contains all core genes for a complete type VI secretion system (T6SS). In contrast, more virulent US isolates retain only remnants of the T6SS (clpB, hcp, vgrG, and vasH) which may have functional implications. Collectively, these results characterize a hypervirulent A. hydrophila pathotype that affects farmed fish on multiple continents.
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Affiliation(s)
| | | | - Sara E Odom
- Department of Biological Sciences, Auburn University Auburn, AL, USA
| | - Jeffery S Terhune
- School of Fisheries, Aquaculture and Aquatic Sciences Auburn, AL, USA
| | | | - Craig A Shoemaker
- Aquatic Animal Health Research Unit, United States Department of Agriculture-Agricultural Research Service Auburn, AL, USA
| | - Dunhua Zhang
- Aquatic Animal Health Research Unit, United States Department of Agriculture-Agricultural Research Service Auburn, AL, USA
| | - De-Hai Xu
- Aquatic Animal Health Research Unit, United States Department of Agriculture-Agricultural Research Service Auburn, AL, USA
| | - Matt J Griffin
- Thad Cochran National Warmwater Aquaculture Center, College of Veterinary Medicine, Mississippi State University Stoneville, MS, USA
| | - Yong-Jie Liu
- College of Veterinary Medicine, Nanjing Agricultural University Nanjing, China
| | - Maria J Figueras
- Departamento de Ciencias Médicas Básicas, Facultad de Medicina y Ciencias de la Salud, IISPV, Universidad Rovira i Virgili Reus, Spain
| | - Scott R Santos
- Department of Biological Sciences, Auburn University Auburn, AL, USA
| | - Joseph C Newton
- Department of Pathobiology, Auburn University Auburn, AL, USA
| | - Mark R Liles
- Department of Biological Sciences, Auburn University Auburn, AL, USA
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20
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Hachani A, Wood TE, Filloux A. Type VI secretion and anti-host effectors. Curr Opin Microbiol 2015; 29:81-93. [PMID: 26722980 DOI: 10.1016/j.mib.2015.11.006] [Citation(s) in RCA: 180] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Revised: 11/25/2015] [Accepted: 11/26/2015] [Indexed: 11/30/2022]
Abstract
Secretion systems play a central role in infectious diseases by enabling pathogenic bacteria to deliver virulence factors into target cells. The type VI secretion system (T6SS) mediates bacterial antagonism in various environments including eukaryotic niches, such as the gut. This molecular machine injects lethal toxins directly in target bacterial cells. It provides an advantage to pathogens encountering the commensal flora of the host and indirectly contributes to colonization and persistence. Yet, the T6SS is not employed for the sole purpose of bacterial killing and several T6SS effectors are dedicated to the subversion of eukaryotic cells. As described for type III and type IV secretion systems, these effectors impede host cell functions and promote immune evasion, thereby enabling successful infection.
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Affiliation(s)
- Abderrahman Hachani
- MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College London, SW72AZ London, United Kingdom; Department of Pathogen Molecular Biology, Faculty of Infection and Tropical Diseases, London School of Hygiene and Tropical Medicine, London WC1E 7HT, United Kingdom; Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Victoria 3000, Australia
| | - Thomas E Wood
- MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College London, SW72AZ London, United Kingdom
| | - Alain Filloux
- MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College London, SW72AZ London, United Kingdom.
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21
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H-NS Silencing of the Salmonella Pathogenicity Island 6-Encoded Type VI Secretion System Limits Salmonella enterica Serovar Typhimurium Interbacterial Killing. Infect Immun 2015; 83:2738-50. [PMID: 25916986 DOI: 10.1128/iai.00198-15] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2015] [Accepted: 04/16/2015] [Indexed: 12/26/2022] Open
Abstract
The secretion of bacterial toxin proteins is achieved by dedicated machineries called secretion systems. The type VI secretion system (T6SS) is a widespread versatile machine used for the delivery of protein toxins to both prokaryotic and eukaryotic cells. In Salmonella enterica serovar Typhimurium, the expression of the T6SS genes is activated during macrophage or mouse infection. Here, we show that the T6SS gene cluster is silenced by the histone-like nucleoid structuring H-NS protein using a combination of reporter fusions, electrophoretic mobility shift assays, DNase footprinting, and fluorescence microscopy. We further demonstrate that derepression of the S. Typhimurium T6SS genes induces T6SS-dependent intoxication of competing bacteria. Our results suggest that relieving T6SS H-NS silencing may be used as a sense-and-kill mechanism that will help S. Typhimurium to homogenize and synchronize the microbial population to gain efficiency during infection.
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22
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Chowdhury R, Mandal RS, Ta A, Das S. An AIL family protein promotes type three secretion system-1-independent invasion and pathogenesis of Salmonella enterica serovar Typhi. Cell Microbiol 2014; 17:486-503. [PMID: 25308535 DOI: 10.1111/cmi.12379] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2014] [Revised: 09/25/2014] [Accepted: 10/04/2014] [Indexed: 02/05/2023]
Abstract
Adhesion and invasion of Intestinal Epithelial Cells (IECs) are critical for the pathogenesis of Salmonella Typhi, the aetiological agent of human typhoid fever. While type three secretion system-1 (T3SS-1) is a major invasion apparatus of Salmonella, independent invasion mechanisms were described for non-typhoidal Salmonellae. Here, we show that T2942, an AIL-like protein of S. Typhi Ty2 strain, is required for adhesion and invasion of cultured IECs. That invasion was T3SS-1 independent was proved by ectopic expression of T2942 in the non-invasive E. coli BL21 and double-mutant Ty2 (Ty2Δt2942ΔinvG) strains. Laminin and fibronectin were identified as the host-binding partners of T2942 with higher affinity for laminin. Standalone function of T2942 was confirmed by cell adhesion of the recombinant protein, while the protein or anti-T2942 antiserum blocked adhesion/invasion of S. Typhi, indicating specificity. A 20-amino acid extracellular loop was required for invasion, while several loop regions of T2942 contributed to adhesion. Further, T2942 cooperates with laminin-binding T2544 for adhesion and T3SS-1 for invasion. Finally, T2942 was required and synergistically worked with T3SS-1 for pathogenesis of S. Typhi in mice. Considering wide distribution of T2942 among clinical strains, the protein or the 20-mer peptide may be suitable for vaccine development.
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Affiliation(s)
- Rimi Chowdhury
- Division of Clinical Medicine, National Institute of Cholera and Enteric Diseases, P-33 Scheme XM C.I.T. Road, Beliaghata Kolkata, 700010, India
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Screening for inhibition of Vibrio cholerae VipA-VipB interaction identifies small-molecule compounds active against type VI secretion. Antimicrob Agents Chemother 2014; 58:4123-30. [PMID: 24798289 DOI: 10.1128/aac.02819-13] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The type VI secretion system (T6SS) is the most prevalent bacterial secretion system and an important virulence mechanism utilized by Gram-negative bacteria, either to target eukaryotic cells or to combat other microbes. The components show much variability, but some appear essential for the function, and two homologues, denoted VipA and VipB in Vibrio cholerae, have been identified in all T6SSs described so far. Secretion is dependent on binding of an α-helical region of VipA to VipB, and in the absence of this binding, both components are degraded within minutes and secretion is ceased. The aim of the study was to investigate if this interaction could be blocked, and we hypothesized that such inhibition would lead to abrogation of T6S. A library of 9,600 small-molecule compounds was screened for their ability to block the binding of VipA-VipB in a bacterial two-hybrid system (B2H). After excluding compounds that showed cytotoxicity toward eukaryotic cells, that inhibited growth of Vibrio, or that inhibited an unrelated B2H interaction, 34 compounds were further investigated for effects on the T6SS-dependent secretion of hemolysin-coregulated protein (Hcp) or of phospholipase A1 activity. Two compounds, KS100 and KS200, showed intermediate or strong effects in both assays. Analogues were obtained, and compounds with potent inhibitory effects in the assays and desirable physicochemical properties as predicted by in silico analysis were identified. Since the compounds specifically target a virulence mechanism without affecting bacterial replication, they have the potential to mitigate the virulence with minimal risk for development of resistance.
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24
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Abstract
Salmonella enterica serovar Typhimurium is a food-borne pathogen that causes severe gastroenteritis. The ability of Salmonella to cause disease depends on two type III secretion systems (T3SSs) encoded in two distinct Salmonella pathogenicity islands, 1 and 2 (SPI1 and SPI2, respectively). S. Typhimurium encodes a solo LuxR homolog, SdiA, which can detect the acyl-homoserine lactones (AHLs) produced by other bacteria and upregulate the rck operon and the srgE gene. SrgE is predicted to encode a protein of 488 residues with a coiled-coil domain between residues 345 and 382. In silico studies have provided conflicting predictions as to whether SrgE is a T3SS substrate. Therefore, in this work, we tested the hypothesis that SrgE is a T3SS effector by two methods, a β-lactamase activity assay and a split green fluorescent protein (GFP) complementation assay. SrgE with β-lactamase fused to residue 40, 100, 150, or 300 was indeed expressed and translocated into host cells, but SrgE with β-lactamase fused to residue 400 or 488 was not expressed, suggesting interference by the coiled-coil domain. Similarly, SrgE with GFP S11 fused to residue 300, but not to residue 488, was expressed and translocated into host cells. With both systems, translocation into host cells was dependent upon SPI2. A phylogenetic analysis indicated that srgE is found only within Salmonella enterica subspecies. It is found sporadically within both typhoidal and nontyphoidal serovars, although the SrgE protein sequences found within typhoidal serovars tend to cluster separately from those found in nontyphoidal serovars, suggesting functional diversification.
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25
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Pezoa D, Blondel CJ, Silva CA, Yang HJ, Andrews-Polymenis H, Santiviago CA, Contreras I. Only one of the two type VI secretion systems encoded in the Salmonella enterica serotype Dublin genome is involved in colonization of the avian and murine hosts. Vet Res 2014; 45:2. [PMID: 24405577 PMCID: PMC3899618 DOI: 10.1186/1297-9716-45-2] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2013] [Accepted: 12/03/2013] [Indexed: 12/23/2022] Open
Abstract
The type VI secretion system (T6SS) is a virulence factor for many Gram-negative bacteria. Salmonella genus harbors five phylogenetically distinct T6SS loci encoded in Salmonella Pathogenicity Islands (SPIs) SPI-6, SPI-19, SPI-20, SPI-21 and SPI-22, which are differentially distributed among serotypes. The T6SSs encoded in SPI-6 and SPI-19 contribute to pathogenesis of serotypes Typhimurium and Gallinarum in mice and chickens, respectively. Salmonella Dublin is a pathogen restricted to cattle where it causes a systemic disease. Also, it can colonize other hosts such as chickens and mice, which can act as reservoirs of this serotype. Salmonella Dublin harbors the genes for both T6SSSPI-6 and T6SSSPI-19. This study has determined the contribution of T6SSSPI-6 and T6SSSPI-19 to host-colonization by Salmonella Dublin using avian and murine models of infection. Competitive index experiments showed that, a mutant strain lacking both T6SSs (∆T6SSSPI-6/∆T6SSSPI-19) presents a strong colonization defect in cecum of chickens, similar to the defect observed for the ∆T6SSSPI-6 mutant, suggesting that this serotype requires a functional T6SSSPI-6 for efficient colonization of the avian gastrointestinal tract. Colonization of mice was also defective, although to a lesser extent than in chickens. In contrast, the T6SSSPI-19 was not necessary for colonization of either chickens or mice. Transfer of T6SSSPI-6, but not T6SSSPI-19, restored the ability of the double mutant to colonize both animal hosts. Our data indicate that Salmonella Dublin requires only the T6SSSPI-6 for efficient colonization of mice and chickens, and that the T6SSSPI-6 and T6SSSPI-19 are not functionally redundant.
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Affiliation(s)
| | | | | | | | | | | | - Inés Contreras
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santos Dumont 964, Santiago, Chile.
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Das C, Dutta A, Rajasingh H, Mande SS. Understanding the sequential activation of Type III and Type VI Secretion Systems in Salmonella typhimurium using Boolean modeling. Gut Pathog 2013; 5:28. [PMID: 24079299 PMCID: PMC3849742 DOI: 10.1186/1757-4749-5-28] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Accepted: 09/14/2013] [Indexed: 01/13/2023] Open
Abstract
Background Three pathogenicity islands, viz. SPI-1 (Salmonella pathogenicity island 1), SPI-2 (Salmonella pathogenicity island 2) and T6SS (Type VI Secretion System), present in the genome of Salmonella typhimurium have been implicated in the virulence of the pathogen. While the regulation of SPI-1 and SPI-2 (both encoding components of the Type III Secretion System - T3SS) are well understood, T6SS regulation is comparatively less studied. Interestingly, inter-connections among the regulatory elements of these three virulence determinants have also been suggested to be essential for successful infection. However, till date, an integrated view of gene regulation involving the regulators of these three secretion systems and their cross-talk is not available. Results In the current study, relevant regulatory information available from literature have been integrated into a single Boolean network, which portrays the dynamics of T3SS (SPI-1 and SPI-2) and T6SS mediated virulence. Some additional regulatory interactions involving a two-component system response regulator YfhA have also been predicted and included in the Boolean network. These predictions are aimed at deciphering the effects of osmolarity on T6SS regulation, an aspect that has been suggested in earlier studies, but the mechanism of which was hitherto unknown. Simulation of the regulatory network was able to recreate in silico the experimentally observed sequential activation of SPI-1, SPI-2 and T6SS. Conclusions The present study integrates relevant gene regulatory data (from literature and our prediction) into a single network, representing the cross-communication between T3SS (SPI-1 and SPI-2) and T6SS. This holistic view of regulatory interactions is expected to improve the current understanding of pathogenesis of S. typhimurium.
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Affiliation(s)
- Chandrani Das
- Bio-Sciences R&D Division, TCS Innovation Labs, Tata Consultancy Services Ltd., 54-B, Hadapsar Industrial Estate, Pune 411013, Maharashtra, India
| | - Anirban Dutta
- Bio-Sciences R&D Division, TCS Innovation Labs, Tata Consultancy Services Ltd., 54-B, Hadapsar Industrial Estate, Pune 411013, Maharashtra, India
| | - Hannah Rajasingh
- Bio-Sciences R&D Division, TCS Innovation Labs, Tata Consultancy Services Ltd., 54-B, Hadapsar Industrial Estate, Pune 411013, Maharashtra, India.,Present address: Novartis Healthcare Pvt. Ltd., #6 Raheja Mindspace, Hitec-city, Hyderabad 500081, India
| | - Sharmila S Mande
- Bio-Sciences R&D Division, TCS Innovation Labs, Tata Consultancy Services Ltd., 54-B, Hadapsar Industrial Estate, Pune 411013, Maharashtra, India
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27
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Pezoa D, Yang HJ, Blondel CJ, Santiviago CA, Andrews-Polymenis HL, Contreras I. The type VI secretion system encoded in SPI-6 plays a role in gastrointestinal colonization and systemic spread of Salmonella enterica serovar Typhimurium in the chicken. PLoS One 2013; 8:e63917. [PMID: 23691117 PMCID: PMC3653874 DOI: 10.1371/journal.pone.0063917] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Accepted: 04/09/2013] [Indexed: 02/06/2023] Open
Abstract
The role of the Salmonella Pathogenicity Islands (SPIs) in pathogenesis of Salmonella enterica Typhimurium infection in the chicken is poorly studied, while many studies have been completed in murine models. The Type VI Secretion System (T6SS) is a recently described protein secretion system in Gram-negative bacteria. The genus Salmonella contains five phylogenetically distinct T6SS encoded in differentially distributed genomic islands. S. Typhimurium harbors a T6SS encoded in SPI-6 (T6SSSPI-6), which contributes to the ability of Salmonella to colonize mice. On the other hand, serotype Gallinarum harbors a T6SS encoded in SPI-19 (T6SSSPI-19) that is required for colonization of chicks. In this work, we investigated the role of T6SSSPI-6 in infection of chicks by S. Typhimurium. Oral infection of White Leghorn chicks showed that a ΔT6SSSPI-6 mutant had reduced colonization of the gut and internal organs, compared with the wild-type strain. Transfer of the intact T6SSSPI-6 gene cluster into the T6SS mutant restored bacterial colonization. In addition, our results showed that transfer of T6SSSPI-19 from S. Gallinarum to the ΔT6SSSPI-6 mutant of S. Typhimurium not only complemented the colonization defect but also resulted in a transient increase in the colonization of the cecum and ileum of chicks at days 1 and 3 post-infection. Our data indicates that T6SSSPI-6 contributes to chicken colonization and suggests that both T6SSSPI-6 and T6SSSPI-19 perform similar functions in vivo despite belonging to different phylogenetic families.
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Affiliation(s)
- David Pezoa
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santiago, Chile
| | - Hee-Jeong Yang
- Department of Microbial and Molecular Pathogenesis, Texas A&M University System Health Science Center, College of Medicine, College Station, Texas, United States of America
| | - Carlos J. Blondel
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santiago, Chile
| | - Carlos A. Santiviago
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santiago, Chile
| | - Helene L. Andrews-Polymenis
- Department of Microbial and Molecular Pathogenesis, Texas A&M University System Health Science Center, College of Medicine, College Station, Texas, United States of America
| | - Inés Contreras
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santiago, Chile
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28
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Miyata ST, Bachmann V, Pukatzki S. Type VI secretion system regulation as a consequence of evolutionary pressure. J Med Microbiol 2013; 62:663-676. [PMID: 23429693 DOI: 10.1099/jmm.0.053983-0] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The type VI secretion system (T6SS) is a mechanism evolved by Gram-negative bacteria to negotiate interactions with eukaryotic and prokaryotic competitors. T6SSs are encoded by a diverse array of bacteria and include plant, animal, human and fish pathogens, as well as environmental isolates. As such, the regulatory mechanisms governing T6SS gene expression vary widely from species to species, and even from strain to strain within a given species. This review concentrates on the four bacterial genera that the majority of recent T6SS regulatory studies have been focused on: Vibrio, Pseudomonas, Burkholderia and Edwardsiella.
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Affiliation(s)
- Sarah T Miyata
- Department of Medical Microbiology and Immunology, 6-22 Heritage Medical Research Centre, University of Alberta, Edmonton, Alberta T6G 2S2, Canada
| | - Verena Bachmann
- Department of Medical Microbiology and Immunology, 6-22 Heritage Medical Research Centre, University of Alberta, Edmonton, Alberta T6G 2S2, Canada
| | - Stefan Pukatzki
- Department of Medical Microbiology and Immunology, 6-22 Heritage Medical Research Centre, University of Alberta, Edmonton, Alberta T6G 2S2, Canada
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The type VI secretion system encoded in Salmonella pathogenicity island 19 is required for Salmonella enterica serotype Gallinarum survival within infected macrophages. Infect Immun 2013; 81:1207-20. [PMID: 23357385 DOI: 10.1128/iai.01165-12] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Salmonella enterica serotype Gallinarum is the causative agent of fowl typhoid, a disease characterized by high morbidity and mortality that causes major economic losses in poultry production. We have reported that S. Gallinarum harbors a type VI secretion system (T6SS) encoded in Salmonella pathogenicity island 19 (SPI-19) that is required for efficient colonization of chicks. In the present study, we aimed to characterize the SPI-19 T6SS functionality and to investigate the mechanisms behind the phenotypes previously observed in vivo. Expression analyses revealed that SPI-19 T6SS core components are expressed and produced under in vitro bacterial growth conditions. However, secretion of the structural/secreted components Hcp1, Hcp2, and VgrG to the culture medium could not be determined, suggesting that additional signals are required for T6SS-dependent secretion of these proteins. In vitro bacterial competition assays failed to demonstrate a role for SPI-19 T6SS in interbacterial killing. In contrast, cell culture experiments with murine and avian macrophages (RAW264.7 and HD11, respectively) revealed production of a green fluorescent protein-tagged version of VgrG soon after Salmonella uptake. Furthermore, infection of RAW264.7 and HD11 macrophages with deletion mutants of SPI-19 or strains with genes encoding specific T6SS core components (clpV and vgrG) revealed that SPI-19 T6SS contributes to S. Gallinarum survival within macrophages at 20 h postuptake. SPI-19 T6SS function was not linked to Salmonella-induced cytotoxicity or cell death of infected macrophages, as has been described for other T6SS. Our data indicate that SPI-19 T6SS corresponds to a novel tool used by Salmonella to survive within host cells.
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Liu J, Guo JT, Li YG, Johnston RN, Liu GR, Liu SL. The type VI secretion system gene cluster ofSalmonella typhimurium: Required for full virulence in mice. J Basic Microbiol 2012; 53:600-7. [DOI: 10.1002/jobm.201200047] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2012] [Accepted: 06/06/2012] [Indexed: 11/11/2022]
Affiliation(s)
| | - Ji-Tao Guo
- Department of Microbiology; Peking University Health Science Center; Beijing; China
| | - Yong-Guo Li
- Genetic Diagnosis Center of First Affiliated Hospital; Harbin Medical University; Harbin; China
| | - Randal N. Johnston
- Department of Biochemistry and Molecular Biology; University of Calgary; Calgary; Canada
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Type VI secretion system-associated gene clusters contribute to pathogenesis of Salmonella enterica serovar Typhimurium. Infect Immun 2012; 80:1996-2007. [PMID: 22493086 DOI: 10.1128/iai.06205-11] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The enteropathogen Salmonella enterica serovar Typhimurium employs a suite of tightly regulated virulence factors within the intracellular compartment of phagocytic host cells resulting in systemic dissemination in mice. A type VI secretion system (T6SS) within Salmonella pathogenicity island 6 (SPI-6) has been implicated in this process; however, the regulatory inputs and the roles of noncore genes in this system are not well understood. Here we describe four clusters of noncore T6SS genes in SPI-6 based on a comparative relationship with the T6SS-3 of Burkholderia mallei and report that the disruption of these genes results in defects in intracellular replication and systemic dissemination in mice. In addition, we show that the expression of the SPI-6-encoded Hcp and VgrG orthologs is enhanced during late stages of macrophage infection. We identify six regions that are transcriptionally active during cell infections and that have regulatory contributions from the regulators of virulence SsrB, PhoP, and SlyA. We show that levels of protein expression are very weak under in vitro conditions and that expression is not enhanced upon the deletion of ssrB, phoP, slyA, qseC, ompR, or hfq, suggesting an unknown activating factor. These data suggest that the SPI-6 T6SS has been integrated into the Salmonella Typhimurium virulence network and customized for host-pathogen interactions through the action of noncore genes.
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