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Lucidi M, Visaggio D, Migliaccio A, Capecchi G, Visca P, Imperi F, Zarrilli R. Pathogenicity and virulence of Acinetobacter baumannii: Factors contributing to the fitness in healthcare settings and the infected host. Virulence 2024; 15:2289769. [PMID: 38054753 PMCID: PMC10732645 DOI: 10.1080/21505594.2023.2289769] [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: 05/17/2023] [Accepted: 11/27/2023] [Indexed: 12/07/2023] Open
Abstract
Acinetobacter baumannii is a common cause of healthcare-associated infections and hospital outbreaks, particularly in intensive care units. Much of the success of A. baumannii relies on its genomic plasticity, which allows rapid adaptation to adversity and stress. The capacity to acquire novel antibiotic resistance determinants and the tolerance to stresses encountered in the hospital environment promote A. baumannii spread among patients and long-term contamination of the healthcare setting. This review explores virulence factors and physiological traits contributing to A. baumannii infection and adaptation to the hospital environment. Several cell-associated and secreted virulence factors involved in A. baumannii biofilm formation, cell adhesion, invasion, and persistence in the host, as well as resistance to xeric stress imposed by the healthcare settings, are illustrated to give reasons for the success of A. baumannii as a hospital pathogen.
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Affiliation(s)
- Massimiliano Lucidi
- Department of Science, Roma Tre University, Rome, Italy
- NBFC, National Biodiversity Future Center, Palermo, Italy
| | - Daniela Visaggio
- Department of Science, Roma Tre University, Rome, Italy
- NBFC, National Biodiversity Future Center, Palermo, Italy
- Santa Lucia Foundation IRCCS, Rome, Italy
| | | | | | - Paolo Visca
- Department of Science, Roma Tre University, Rome, Italy
- NBFC, National Biodiversity Future Center, Palermo, Italy
- Santa Lucia Foundation IRCCS, Rome, Italy
| | - Francesco Imperi
- Department of Science, Roma Tre University, Rome, Italy
- NBFC, National Biodiversity Future Center, Palermo, Italy
- Santa Lucia Foundation IRCCS, Rome, Italy
| | - Raffaele Zarrilli
- Department of Public Health, University of Naples Federico II, Naples, Italy
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Zhang C, Datta S, Ratcliff WC, Hammer BK. Constitutive expression of the Type VI Secretion System carries no measurable fitness cost in Vibrio cholerae. Ecol Evol 2024; 14:e11081. [PMID: 38435022 PMCID: PMC10905242 DOI: 10.1002/ece3.11081] [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: 06/07/2023] [Revised: 02/03/2024] [Accepted: 02/13/2024] [Indexed: 03/05/2024] Open
Abstract
The Type VI Secretion System (T6SS) is a widespread and highly effective mechanism of microbial warfare; it confers the ability to efficiently kill susceptible cells within close proximity. Due to its large physical size, complexity, and ballistic basis for intoxication, it has widely been assumed to incur significant growth costs in the absence of improved competitive outcomes. In this study, we precisely examine the fitness costs of constitutive T6SS firing in the bacterium Vibrio cholerae. We find that, contrary to expectations, constitutive expression of the T6SS has a negligible impact on growth, reducing growth fitness by 0.025 ± 0.5% (95% CI) relative to a T6SS- control. Mathematical modeling of microbial populations demonstrates that, due to clonal interference, constitutive expression of the T6SS will often be neutral, with little impact on evolutionary outcomes. Our findings underscore the importance of precisely measuring the fitness costs of microbial social behaviors and help explain the prevalence of the T6SS across Gram-negative bacteria.
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Affiliation(s)
- Christopher Zhang
- School of Biological SciencesGeorgia Institute of TechnologyAtlantaGeorgiaUSA
- Interdisciplinary Graduate Program in Quantitative BiosciencesGeorgia Institute of TechnologyAtlantaGeorgiaUSA
| | - Sayantan Datta
- School of Biological SciencesGeorgia Institute of TechnologyAtlantaGeorgiaUSA
- Interdisciplinary Graduate Program in Quantitative BiosciencesGeorgia Institute of TechnologyAtlantaGeorgiaUSA
| | - William C. Ratcliff
- School of Biological SciencesGeorgia Institute of TechnologyAtlantaGeorgiaUSA
| | - Brian K. Hammer
- School of Biological SciencesGeorgia Institute of TechnologyAtlantaGeorgiaUSA
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Li P, Zhang S, Wang J, Al-Shamiri MM, Luo K, Liu S, Mi P, Wu X, Liu H, Tian H, Han B, Lei J, Han S, Han L. The role of type VI secretion system genes in antibiotic resistance and virulence in Acinetobacter baumannii clinical isolates. Front Cell Infect Microbiol 2024; 14:1297818. [PMID: 38384301 PMCID: PMC10879597 DOI: 10.3389/fcimb.2024.1297818] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Accepted: 01/23/2024] [Indexed: 02/23/2024] Open
Abstract
Introduction The type VI secretion system (T6SS) is a crucial virulence factor in the nosocomial pathogen Acinetobacter baumannii. However, its association with drug resistance is less well known. Notably, the roles that different T6SS components play in the process of antimicrobial resistance, as well as in virulence, have not been systematically revealed. Methods The importance of three representative T6SS core genes involved in the drug resistance and virulence of A. baumannii, namely, tssB, tssD (hcp), and tssM was elucidated. Results A higher ratio of the three core genes was detected in drug-resistant strains than in susceptible strains among our 114 A. baumannii clinical isolates. Upon deletion of tssB in AB795639, increased antimicrobial resistance to cefuroxime and ceftriaxone was observed, alongside reduced resistance to gentamicin. The ΔtssD mutant showed decreased resistance to ciprofloxacin, norfloxacin, ofloxacin, tetracycline, and doxycycline, but increased resistance to tobramycin and streptomycin. The tssM-lacking mutant showed an increased sensitivity to ofloxacin, polymyxin B, and furazolidone. In addition, a significant reduction in biofilm formation was observed only with the ΔtssM mutant. Moreover, the ΔtssM strain, followed by the ΔtssD mutant, showed decreased survival in human serum, with attenuated competition with Escherichia coli and impaired lethality in Galleria mellonella. Discussion The above results suggest that T6SS plays an important role, participating in the antibiotic resistance of A. baumannii, especially in terms of intrinsic resistance. Meanwhile, tssM and tssD contribute to bacterial virulence to a greater degree, with tssM being associated with greater importance.
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Affiliation(s)
- Pu Li
- School of Public Health, Xi’an Jiaotong University Health Science Center, Xi’an, Shaanxi, China
| | - Sirui Zhang
- Department of Microbiology and Immunology, School of Basic Medical Sciences, Xi’an Jiaotong University Health Science Center, Xi’an, Shaanxi, China
| | - Jingdan Wang
- School of Public Health, Xi’an Jiaotong University Health Science Center, Xi’an, Shaanxi, China
| | - Mona Mohamed Al-Shamiri
- Department of Microbiology and Immunology, School of Basic Medical Sciences, Xi’an Jiaotong University Health Science Center, Xi’an, Shaanxi, China
| | - Kai Luo
- Department of Microbiology and Immunology, School of Basic Medical Sciences, Xi’an Jiaotong University Health Science Center, Xi’an, Shaanxi, China
| | - Shuyan Liu
- Department of Microbiology and Immunology, School of Basic Medical Sciences, Xi’an Jiaotong University Health Science Center, Xi’an, Shaanxi, China
| | - Peng Mi
- Department of Microbiology and Immunology, School of Basic Medical Sciences, Xi’an Jiaotong University Health Science Center, Xi’an, Shaanxi, China
- Department of Laboratory Medicine, Shaanxi Provincial People’s Hospital, Xi’an, China
| | - Xiaokang Wu
- Department of Laboratory Medicine, the Second Affiliated Hospital of Xi’an Jiaotong University, Xi’an, China
| | - Haiping Liu
- Department of Microbiology and Immunology, School of Basic Medical Sciences, Xi’an Jiaotong University Health Science Center, Xi’an, Shaanxi, China
- Department of Laboratory Medicine, Xi’an Daxing Hospital, Xi’an, China
| | - Huohuan Tian
- Department of Respiratory and Critical Care Medicine, West China Hospital, Sichuan University, Chengdu, China
| | - Bei Han
- School of Public Health, Xi’an Jiaotong University Health Science Center, Xi’an, Shaanxi, China
| | - Jin’e Lei
- Department of Laboratory Medicine, the First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, China
| | - Shaoshan Han
- Department of Hepatobiliary Surgery, the First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, China
| | - Lei Han
- Department of Microbiology and Immunology, School of Basic Medical Sciences, Xi’an Jiaotong University Health Science Center, Xi’an, Shaanxi, China
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Xiong X, Wan W, Ding B, Cai M, Lu M, Liu W. Type VI secretion system drives bacterial diversity and functions in multispecies biofilms. Microbiol Res 2024; 279:127570. [PMID: 38096690 DOI: 10.1016/j.micres.2023.127570] [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: 10/06/2023] [Revised: 12/01/2023] [Accepted: 12/06/2023] [Indexed: 12/23/2023]
Abstract
Type VI secretion system (T6SS) plays an essential role in interspecies interactions and provides an advantage for a strain with T6SS in multispecies biofilms. However, how T6SS drives the bacterial community structure and functions in multispecies biofilms still needs to be determined. Using gene deletion and Illumina sequencing technique, we estimated bacterial community responses in multispecies biofilms to T6SS by introducing T6SS-containing Pseudomonas putida KT2440. Results showed that the niche structure shifts of multispecies biofilms were remarkably higher in the presence of T6SS than in the absence of T6SS. The presence of T6SS significantly drove the variation in microbial composition, reduced the alpha-diversity of bacterial communities in multispecies biofilms, and separately decreased and increased the relative abundance of Proteobacteria and Bacteroidota. Co-occurrence network analysis with inferred putative bacterial interactions indicated that P. putida KT2440 mainly displayed strong negative associations with the genera of Psychrobacter, Cellvibrio, Stenotrophomonas, and Brevundimonas. Moreover, the function redundancy index of the bacterial community was strikingly higher in the presence of T6SS than in the absence of T6SS, regardless of whether relative abundances of bacterial taxa were inhibited or promoted. Remarkably, the increased metabolic network similarity with T6SS-containing P. putida KT2440 could enhance the antibacterial activity of P. putida KT2440 on other bacterial taxa. Our findings extend knowledge of microbial adaptation strategies to potential bacterial weapons and could contribute to predicting biodiversity loss and change in ecological functions caused by T6SS.
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Affiliation(s)
- Xiang Xiong
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430070, PR China; Danjiangkou Wetland Ecosystem Field Scientific Observation and Research Station, Chinese Academy of Sciences & Hubei Province, Wuhan 430070, PR China
| | - Wenjie Wan
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430070, PR China; Danjiangkou Wetland Ecosystem Field Scientific Observation and Research Station, Chinese Academy of Sciences & Hubei Province, Wuhan 430070, PR China
| | - Bangjing Ding
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430070, PR China; Danjiangkou Wetland Ecosystem Field Scientific Observation and Research Station, Chinese Academy of Sciences & Hubei Province, Wuhan 430070, PR China
| | - Miaomiao Cai
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430070, PR China; Danjiangkou Wetland Ecosystem Field Scientific Observation and Research Station, Chinese Academy of Sciences & Hubei Province, Wuhan 430070, PR China
| | - Mingzhu Lu
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430070, PR China; Danjiangkou Wetland Ecosystem Field Scientific Observation and Research Station, Chinese Academy of Sciences & Hubei Province, Wuhan 430070, PR China
| | - Wenzhi Liu
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430070, PR China; Danjiangkou Wetland Ecosystem Field Scientific Observation and Research Station, Chinese Academy of Sciences & Hubei Province, Wuhan 430070, PR China.
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Liu W, Li M, Cao S, Ishaq HM, Zhao H, Yang F, Liu L. The Biological and Regulatory Role of Type VI Secretion System of Klebsiella pneumoniae. Infect Drug Resist 2023; 16:6911-6922. [PMID: 37928603 PMCID: PMC10624183 DOI: 10.2147/idr.s426657] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Accepted: 09/30/2023] [Indexed: 11/07/2023] Open
Abstract
Bacteria communicate with their surroundings through diverse secretory systems, and the recently discovered Type VI Secretion System (T6SS) has gained significant attention. Klebsiella pneumoniae (K. pneumoniae), an opportunistic pathogen known for causing severe infections in both hospital and animal settings, possesses this intriguing T6SS. This system equips K. pneumoniae with a formidable armory of protein-based weaponry, enabling the delivery of toxins into neighboring cells, thus granting a substantial competitive advantage. Remarkably, the T6SS has also been associated with K. pneumoniae's ability to form biofilms and acquire resistance against antibiotics. However, the precise effects of the T6SS on K. pneumoniae's functions remain inadequately studied, despite research efforts to understand the intricacies of these mechanisms. This comprehensive review aims to provide an overview of the current knowledge regarding the biological functions and regulatory mechanisms of the T6SS in K. pneumoniae.
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Affiliation(s)
- Wenke Liu
- Department of Pathogenic Biology, School of Basic Medical Sciences, Xinxiang Medical University, Xinxiang, People’s Republic of China
| | - Min Li
- Department of Pathogenic Biology, School of Basic Medical Sciences, Xinxiang Medical University, Xinxiang, People’s Republic of China
| | - Shiwen Cao
- Department of Pathogenic Biology, School of Basic Medical Sciences, Xinxiang Medical University, Xinxiang, People’s Republic of China
| | - Hafiz Muhammad Ishaq
- Faculty of Veterinary and Animal Sciences, Muhammad Nawaz Shareef University of Agriculture, Multan, Pakistan
| | - Huajie Zhao
- Department of Pathogenic Biology, School of Basic Medical Sciences, Xinxiang Medical University, Xinxiang, People’s Republic of China
| | - Fan Yang
- Department of Pathogenic Biology, School of Basic Medical Sciences, Xinxiang Medical University, Xinxiang, People’s Republic of China
| | - Liang Liu
- Department of Pathogenic Biology, School of Basic Medical Sciences, Xinxiang Medical University, Xinxiang, People’s Republic of China
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Kandolo O, Cherrak Y, Filella-Merce I, Le Guenno H, Kosta A, Espinosa L, Santucci P, Verthuy C, Lebrun R, Nilges M, Pellarin R, Durand E. Acinetobacter type VI secretion system comprises a non-canonical membrane complex. PLoS Pathog 2023; 19:e1011687. [PMID: 37769028 PMCID: PMC10564176 DOI: 10.1371/journal.ppat.1011687] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Revised: 10/10/2023] [Accepted: 09/14/2023] [Indexed: 09/30/2023] Open
Abstract
A. baumannii can rapidly acquire new resistance mechanisms and persist on abiotic surface, enabling the colonization of asymptomatic human host. In Acinetobacter the type VI secretion system (T6SS) is involved in twitching, surface motility and is used for interbacterial competition allowing the bacteria to uptake DNA. A. baumannii possesses a T6SS that has been well studied for its regulation and specific activity, but little is known concerning its assembly and architecture. The T6SS nanomachine is built from three architectural sub-complexes. Unlike the baseplate (BP) and the tail-tube complex (TTC), which are inherited from bacteriophages, the membrane complex (MC) originates from bacteria. The MC is the most external part of the T6SS and, as such, is subjected to evolution and adaptation. One unanswered question on the MC is how such a gigantesque molecular edifice is inserted and crosses the bacterial cell envelope. The A. baumannii MC lacks an essential component, the TssJ lipoprotein, which anchors the MC to the outer membrane. In this work, we studied how A. baumannii compensates the absence of a TssJ. We have characterized for the first time the A. baumannii's specific T6SS MC, its unique characteristic, its membrane localization, and assembly dynamics. We also defined its composition, demonstrating that its biogenesis employs three Acinetobacter-specific envelope-associated proteins that define an intricate network leading to the assembly of a five-proteins membrane super-complex. Our data suggest that A. baumannii has divided the function of TssJ by (1) co-opting a new protein TsmK that stabilizes the MC and by (2) evolving a new domain in TssM for homo-oligomerization, a prerequisite to build the T6SS channel. We believe that the atypical species-specific features we report in this study will have profound implication in our understanding of the assembly and evolutionary diversity of different T6SSs, that warrants future investigation.
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Affiliation(s)
- Ona Kandolo
- Laboratoire d’Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie, Bioénergies and Biotechnologie (IM2B), Aix-Marseille Université, Centre National de la Recherche Scientifique (CNRS)-UMR 7255, Marseille, France
| | - Yassine Cherrak
- Laboratoire d’Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie, Bioénergies and Biotechnologie (IM2B), Aix-Marseille Université, Centre National de la Recherche Scientifique (CNRS)-UMR 7255, Marseille, France
| | - Isaac Filella-Merce
- Institut Pasteur, Structural Bioinformatics Unit, Department of Structural Biology and Chemistry, Paris, France
- Sorbonne Université, Collège doctoral, Paris, France
| | - Hugo Le Guenno
- Microscopy Core Facility, Aix Marseille Univ, CNRS, Institut de Microbiologie de la Méditerranée, Marseille Cedex 20, France
| | - Artemis Kosta
- Microscopy Core Facility, Aix Marseille Univ, CNRS, Institut de Microbiologie de la Méditerranée, Marseille Cedex 20, France
| | - Leon Espinosa
- Laboratoire de Chimie Bactérienne (LCB), Institut de Microbiologie, Bioénergies and Biotechnologie (IM2B), Aix-Marseille Université, Centre National de la Recherche Scientifique, Marseille, France
| | - Pierre Santucci
- Laboratoire d’Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie, Bioénergies and Biotechnologie (IM2B), Aix-Marseille Université, Centre National de la Recherche Scientifique (CNRS)-UMR 7255, Marseille, France
| | - Christophe Verthuy
- Proteomic Core Facility IMM, Marseille Protéomique (MaP), Aix Marseille Univ, Marseille Cedex 20, France
| | - Régine Lebrun
- Proteomic Core Facility IMM, Marseille Protéomique (MaP), Aix Marseille Univ, Marseille Cedex 20, France
| | - Michael Nilges
- Institut Pasteur, Structural Bioinformatics Unit, Department of Structural Biology and Chemistry, Paris, France
| | - Riccardo Pellarin
- Institut Pasteur, Structural Bioinformatics Unit, Department of Structural Biology and Chemistry, Paris, France
| | - Eric Durand
- Laboratoire d’Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie, Bioénergies and Biotechnologie (IM2B), Aix-Marseille Université, Centre National de la Recherche Scientifique (CNRS)-UMR 7255, Marseille, France
- Laboratoire d’Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie, Bioénergies and Biotechnologie (IM2B), Aix-Marseille Université, Institut National de la Santé et de la Recherche Médicale (INSERM), Marseille, France
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Hespanhol JT, Nóbrega-Silva L, Bayer-Santos E. Regulation of type VI secretion systems at the transcriptional, posttranscriptional and posttranslational level. MICROBIOLOGY (READING, ENGLAND) 2023; 169:001376. [PMID: 37552221 PMCID: PMC10482370 DOI: 10.1099/mic.0.001376] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Accepted: 07/25/2023] [Indexed: 08/09/2023]
Abstract
Bacteria live in complex polymicrobial communities and are constantly competing for resources. The type VI secretion system (T6SS) is a widespread antagonistic mechanism used by Gram-negative bacteria to gain an advantage over competitors. T6SSs translocate toxic effector proteins inside target prokaryotic cells in a contact-dependent manner. In addition, some T6SS effectors can be secreted extracellularly and contribute to the scavenging scarce metal ions. Bacteria deploy their T6SSs in different situations, categorizing these systems into offensive, defensive and exploitative. The great variety of bacterial species and environments occupied by such species reflect the complexity of regulatory signals and networks that control the expression and activation of the T6SSs. Such regulation is tightly controlled at the transcriptional, posttranscriptional and posttranslational level by abiotic (e.g. pH, iron) or biotic (e.g. quorum-sensing) cues. In this review, we provide an update on the current knowledge about the regulatory networks that modulate the expression and activity of T6SSs across several species, focusing on systems used for interbacterial competition.
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Affiliation(s)
- Julia Takuno Hespanhol
- Department of Microbiology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo 05508-900, Brazil
| | - Luize Nóbrega-Silva
- Department of Microbiology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo 05508-900, Brazil
| | - Ethel Bayer-Santos
- Department of Microbiology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo 05508-900, Brazil
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8
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He W, Wu K, Ouyang Z, Bai Y, Luo W, Wu D, An H, Guo Y, Jiao M, Qin Q, Zhang J, Wu Y, She J, Hwang PM, Zheng F, Zhu L, Wen Y. Structure and assembly of type VI secretion system cargo delivery vehicle. Cell Rep 2023; 42:112781. [PMID: 37421630 DOI: 10.1016/j.celrep.2023.112781] [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: 10/23/2022] [Revised: 05/06/2023] [Accepted: 06/25/2023] [Indexed: 07/10/2023] Open
Abstract
Type VI secretion system is widely used in Gram-negative bacteria for injecting toxic effectors into neighboring prokaryotic or eukaryotic cells. Various effectors can be loaded onto the T6SS delivery tube via its core components: Hcp, VgrG, or PAAR. Here, we report 2.8-Å resolution cryo-EM structure of intact T6SS Hcp5-VgrG-PAAR cargo delivery system and crystal structure of unbound Hcp5 from B. fragilis NCTC 9343. Loading of Hcp5 hexameric ring onto VgrG causes expansion of its inner cavity and external surface, explaining how structural changes could be propagated to regulate co-polymerization and surrounding contractile sheath. High-affinity binding between Hcp and VgrG causes entropically unfavorable structuring of long loops. Furthermore, interactions between VgrG trimer and Hcp hexamer are asymmetric, with three of the six Hcp monomers exhibiting a major loop flip. Our study provides insights into the assembly, loading, and firing of T6SS nanomachine that contributes to bacterial inter-species competition and host interactions.
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Affiliation(s)
- Wenbo He
- Center for Microbiome Research of Med-X Institute, Shaanxi Provincial Key Laboratory of Sepsis in Critical Care Medicine, The First Affiliated Hospital, Xi'an Jiaotong University, Xi'an 710061, China
| | - Ke Wu
- Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, China
| | - Zhenlin Ouyang
- Center for Microbiome Research of Med-X Institute, Shaanxi Provincial Key Laboratory of Sepsis in Critical Care Medicine, The First Affiliated Hospital, Xi'an Jiaotong University, Xi'an 710061, China
| | - Yixin Bai
- Center for Microbiome Research of Med-X Institute, Shaanxi Provincial Key Laboratory of Sepsis in Critical Care Medicine, The First Affiliated Hospital, Xi'an Jiaotong University, Xi'an 710061, China
| | - Wen Luo
- Department of Oncology, The Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi, China
| | - Di Wu
- Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, China
| | - Hao An
- Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, China
| | - Yucheng Guo
- The Key Laboratory of Environment and Genes Related to Disease of Ministry of Education Health Science Center, Xi'an Jiaotong University, Xi'an 710061, China
| | - Min Jiao
- Center for Microbiome Research of Med-X Institute, Shaanxi Provincial Key Laboratory of Sepsis in Critical Care Medicine, The First Affiliated Hospital, Xi'an Jiaotong University, Xi'an 710061, China
| | - Qian Qin
- Center for Microbiome Research of Med-X Institute, Shaanxi Provincial Key Laboratory of Sepsis in Critical Care Medicine, The First Affiliated Hospital, Xi'an Jiaotong University, Xi'an 710061, China
| | - Jiaxin Zhang
- The Key Laboratory of Environment and Genes Related to Disease of Ministry of Education Health Science Center, Xi'an Jiaotong University, Xi'an 710061, China
| | - Yi Wu
- The Key Laboratory of Environment and Genes Related to Disease of Ministry of Education Health Science Center, Xi'an Jiaotong University, Xi'an 710061, China
| | - Junjun She
- Center for Microbiome Research of Med-X Institute, Shaanxi Provincial Key Laboratory of Sepsis in Critical Care Medicine, The First Affiliated Hospital, Xi'an Jiaotong University, Xi'an 710061, China
| | - Peter M Hwang
- Department of Biochemistry, Faculty of Medicine & Dentistry, Edmonton, AB T6G 2R3, Canada
| | - Fang Zheng
- The Key Laboratory of Environment and Genes Related to Disease of Ministry of Education Health Science Center, Xi'an Jiaotong University, Xi'an 710061, China
| | - Li Zhu
- Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, China; Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Electron Microscopy Centre of Lanzhou University, Lanzhou University, Lanzhou 730000, China.
| | - Yurong Wen
- Center for Microbiome Research of Med-X Institute, Shaanxi Provincial Key Laboratory of Sepsis in Critical Care Medicine, The First Affiliated Hospital, Xi'an Jiaotong University, Xi'an 710061, China; The Key Laboratory of Environment and Genes Related to Disease of Ministry of Education Health Science Center, Xi'an Jiaotong University, Xi'an 710061, China.
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9
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Dutka P, Liu Y, Maggi S, Ghosal D, Wang J, Carter SD, Zhao W, Vijayrajratnam S, Vogel JP, Jensen GJ. Structure and Function of the Dot/Icm T4SS. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.22.533729. [PMID: 36993699 PMCID: PMC10055428 DOI: 10.1101/2023.03.22.533729] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/31/2023]
Abstract
The Legionella pneumophila Dot/Icm type IV secretion system (T4SS) delivers effector proteins into host cells during infection. Despite its significance as a potential drug target, our current understanding of its atomic structure is limited to isolated subcomplexes. In this study, we used subtomogram averaging and integrative modeling to construct a nearly-complete model of the Dot/Icm T4SS accounting for seventeen protein components. We locate and provide insights into the structure and function of six new components including DotI, DotJ, DotU, IcmF, IcmT, and IcmX. We find that the cytosolic N-terminal domain of IcmF, a key protein forming a central hollow cylinder, interacts with DotU, providing insight into previously uncharacterized density. Furthermore, our model, in combination with analyses of compositional heterogeneity, explains how the cytoplasmic ATPase DotO is connected to the periplasmic complex via interactions with membrane-bound DotI/DotJ proteins. Coupled with in situ infection data, our model offers new insights into the T4SS-mediated secretion mechanism.
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Affiliation(s)
- Przemysław Dutka
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, USA
| | - Yuxi Liu
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA
| | - Stefano Maggi
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, USA
| | - Debnath Ghosal
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA
- Present address: Department of Biochemistry and Pharmacology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, VIC, Australia
| | - Jue Wang
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, USA
| | - Stephen D. Carter
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA
- Present address: MRC-University of Glasgow Centre for Virus Research, School of Infection and Immunity, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, Scotland, UK
| | - Wei Zhao
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA
| | | | - Joseph P. Vogel
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Grant J. Jensen
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, USA
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10
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Seng R, Phunpang R, Saiprom N, Dulsuk A, Chewapreecha C, Thaipadungpanit J, Batty EM, Chantratita W, West TE, Chantratita N. Phenotypic and genetic alterations of Burkholderia pseudomallei in patients during relapse and persistent infections. Front Microbiol 2023; 14:1103297. [PMID: 36814569 PMCID: PMC9939903 DOI: 10.3389/fmicb.2023.1103297] [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: 11/20/2022] [Accepted: 01/09/2023] [Indexed: 02/09/2023] Open
Abstract
The bacterium Burkholderia pseudomallei is the causative agent of melioidosis, a severe tropical disease associated with high mortality and relapse and persistent infections. Treatment of melioidosis requires prolonged antibiotic therapy; however, little is known about relapse and persistent infections, particularly the phenotypic and genetic alterations of B. pseudomallei in patients. In this study, we performed pulsed-field gel electrophoresis (PFGE) to compare the bacterial genotype between the initial isolate and the subsequent isolate from each of 23 suspected recurrent and persistent melioidosis patients in Northeast Thailand. We used whole-genome sequencing (WGS) to investigate multilocus sequence types and genetic alterations of within-host strain pairs. We also investigated the bacterial phenotypes associated with relapse and persistent infections, including multinucleated giant cell (MNGC) formation efficiency and intracellular multiplication. We first identified 13 (1.2%) relapse, 7 (0.7%) persistent, and 3 (0.3%) reinfection patients from 1,046 survivors. Each of the 20 within-host strain pairs from patients with relapse and persistent infections shared the same genotype, suggesting that the subsequent isolates arise from the infecting isolate. Logistic regression analysis of clinical data revealed regimen and duration of oral antibiotic therapies as risk factors associated with relapse and persistent infections. WGS analysis demonstrated 17 within-host genetic alteration events in 6 of 20 paired isolates, including a relatively large deletion and 16 single-nucleotide polymorphism (stocktickerSNP) mutations distributed across 12 genes. In 1 of 20 paired isolates, we observed significantly increased cell-to-cell fusion and intracellular replication in the second isolate compared with the initial isolate from a patient with persistent infection. WGS analysis suggested that a non-synonymous mutation in the tssB-5 gene, which encoded an essential component of the type VI secretion system, may be associated with the increased intracellular replication and MNGC formation efficiency of the second isolate of the patient. This information provides insights into genetic and phenotypic alterations in B. pseudomallei in human melioidosis, which may represent a bacterial strategy for persistent and relapse infections.
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Affiliation(s)
- Rathanin Seng
- Department of Microbiology and Immunology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Rungnapa Phunpang
- Department of Microbiology and Immunology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Natnaree Saiprom
- Department of Microbiology and Immunology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Adul Dulsuk
- Department of Microbiology and Immunology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Claire Chewapreecha
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Parasites and Microbes, Wellcome Sanger Institute, Cambridge, United Kingdom
- Department of Clinical Tropical Medicine, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Janjira Thaipadungpanit
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Department of Clinical Tropical Medicine, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Elizabeth M. Batty
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Nuffield Department of Medicine, Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, United Kingdom
| | - Wasun Chantratita
- Center for Medical Genomics, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Bangkok, Thailand
| | - T. Eoin West
- Department of Microbiology and Immunology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Medicine, University of Washington, Seattle, WA, United States
- Department of Global Health, University of Washington, Seattle, WA, United States
| | - Narisara Chantratita
- Department of Microbiology and Immunology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
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11
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Guckes KR, Miyashiro TI. The type-VI secretion system of the beneficial symbiont Vibrio fischeri. MICROBIOLOGY (READING, ENGLAND) 2023; 169:10.1099/mic.0.001302. [PMID: 36809081 PMCID: PMC9972734 DOI: 10.1099/mic.0.001302] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
The mutualistic symbiosis between the Hawaiian bobtail squid Euprymna scolopes and the marine bacterium Vibrio fischeri is a powerful experimental system for determining how intercellular interactions impact animal-bacterial associations. In nature, this symbiosis features multiple strains of V. fischeri within each adult animal, which indicates that different strains initially colonize each squid. Various studies have demonstrated that certain strains of V. fischeri possess a type-VI secretion system (T6SS), which can inhibit other strains from establishing symbiosis within the same host habitat. The T6SS is a bacterial melee weapon that enables a cell to kill adjacent cells by translocating toxic effectors via a lancet-like apparatus. This review describes the progress that has been made in understanding the factors that govern the structure and expression of the T6SS in V. fischeri and its effect on the symbiosis.
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12
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Li P, Zhang S, Wang J, Al-Shamiri MM, Han B, Chen Y, Han S, Han L. Uncovering the Secretion Systems of Acinetobacter baumannii: Structures and Functions in Pathogenicity and Antibiotic Resistance. Antibiotics (Basel) 2023; 12:antibiotics12020195. [PMID: 36830106 PMCID: PMC9952577 DOI: 10.3390/antibiotics12020195] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Revised: 01/06/2023] [Accepted: 01/16/2023] [Indexed: 01/19/2023] Open
Abstract
Infections led by Acinetobacter baumannii strains are of great concern in healthcare environments due to the strong ability of the bacteria to spread through different apparatuses and develop drug resistance. Severe diseases can be caused by A. baumannii in critically ill patients, but its biological process and mechanism are not well understood. Secretion systems have recently been demonstrated to be involved in the pathogenic process, and five types of secretion systems out of the currently known six from Gram-negative bacteria have been found in A. baumannii. They can promote the fitness and pathogenesis of the bacteria by releasing a variety of effectors. Additionally, antibiotic resistance is found to be related to some types of secretion systems. In this review, we describe the genetic and structural compositions of the five secretion systems that exist in Acinetobacter. In addition, the function and molecular mechanism of each secretion system are summarized to explain how they enable these critical pathogens to overcome eukaryotic hosts and prokaryotic competitors to cause diseases.
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Affiliation(s)
- Pu Li
- School of Public Health, Xi’an Jiaotong University Health Science Center, Xi’an 710061, China
| | - Sirui Zhang
- Department of Microbiology and Immunology, School of Basic Medical Sciences, Xi’an Jiaotong University Health Science Center, Xi’an 710061, China
| | - Jingdan Wang
- School of Public Health, Xi’an Jiaotong University Health Science Center, Xi’an 710061, China
| | - Mona Mohamed Al-Shamiri
- Department of Microbiology and Immunology, School of Basic Medical Sciences, Xi’an Jiaotong University Health Science Center, Xi’an 710061, China
| | - Bei Han
- School of Public Health, Xi’an Jiaotong University Health Science Center, Xi’an 710061, China
| | - Yanjiong Chen
- Department of Microbiology and Immunology, School of Basic Medical Sciences, Xi’an Jiaotong University Health Science Center, Xi’an 710061, China
| | - Shaoshan Han
- Department of Hepatobiliary Surgery, The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an 710061, China
| | - Lei Han
- Department of Microbiology and Immunology, School of Basic Medical Sciences, Xi’an Jiaotong University Health Science Center, Xi’an 710061, China
- Correspondence:
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13
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Liu M, Wang H, Liu Y, Tian M, Wang Z, Shu RD, Zhao MY, Chen WD, Wang H, Wang H, Fu Y. The phospholipase effector Tle1 Vc promotes Vibrio cholerae virulence by killing competitors and impacting gene expression. Gut Microbes 2023; 15:2241204. [PMID: 37526354 PMCID: PMC10395195 DOI: 10.1080/19490976.2023.2241204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Accepted: 07/20/2023] [Indexed: 08/02/2023] Open
Abstract
Vibrio cholerae utilizes the Type VI secretion system (T6SS) to gain an advantage in interbacterial competition by delivering anti-prokaryotic effectors in a contact-dependent manner. However, the impact of T6SS and its secreted effectors on physiological behavior remains poorly understood. In this study, we present Tle1Vc, a phospholipase effector in atypical pathogenic V. cholerae E1 that is secreted by T6SS via its interaction with VgrG1E1. Tle1Vc contains a DUF2235 domain and belongs to the Tle1 (type VI lipase effector) family. Bacterial toxicity assays, lipase activity assays and site-directed mutagenesis revealed that Tle1Vc possessed phospholipase A1 activity and phospholipase A2 activity, and that Tle1Vc-induced toxicity required a serine residue (S356) and two aspartic acid residues (D417 and D496). Cells intoxication with Tle1Vc lead to membrane depolarization and alter membrane permeability. Tli1tox-, a cognate immunity protein, directly interacts with Tle1Vc to neutralize its toxicity. Moreover, Tle1Vc can kill multiple microorganisms by T6SS and promote in vivo fitness of V. cholerae through mediating antibacterial activity. Tle1Vc induces bacterial motility by increasing the expression of flagellar-related genes independently of functional T6SS and the tit-for-tat (TFT) response, where Pseudomonas aeruginosa uses its T6SS-H1 cluster to counterattack other offensive attackers. Our study also demonstrated that the physical puncture of E1 T6SS can induce a moderate TFT response, which is essential to the Tle1Vc-mediated strong TFT response, maximizing effector functions. Overall, our study characterized the antibacterial mechanism of phospholipase effector Tle1Vc and its multiple physiological significance.
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Affiliation(s)
- Ming Liu
- School of Medicine, Southern University of Science and Technology, Shenzhen, China
| | - Heng Wang
- School of Medicine, Southern University of Science and Technology, Shenzhen, China
| | - Ying Liu
- School of Medicine, Southern University of Science and Technology, Shenzhen, China
| | - Miao Tian
- School of Medicine, Southern University of Science and Technology, Shenzhen, China
| | - Zhao Wang
- School of Medicine, Southern University of Science and Technology, Shenzhen, China
| | - Run-Dong Shu
- College of Life Sciences, Nanjing Agricultural University, Nanjing, China
| | - Meng-Yu Zhao
- School of Medicine, Southern University of Science and Technology, Shenzhen, China
| | - Wei-Di Chen
- School of Medicine, Southern University of Science and Technology, Shenzhen, China
| | - Hao Wang
- School of Medicine, Southern University of Science and Technology, Shenzhen, China
| | - Hui Wang
- College of Life Sciences, Nanjing Agricultural University, Nanjing, China
| | - Yang Fu
- School of Medicine, Southern University of Science and Technology, Shenzhen, China
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14
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Hespanhol JT, Sanchez-Limache DE, Nicastro GG, Mead L, Llontop EE, Chagas-Santos G, Farah CS, de Souza RF, Galhardo RDS, Lovering AL, Bayer-Santos E. Antibacterial T6SS effectors with a VRR-Nuc domain are structure-specific nucleases. eLife 2022; 11:e82437. [PMID: 36226828 PMCID: PMC9635880 DOI: 10.7554/elife.82437] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Accepted: 10/09/2022] [Indexed: 11/21/2022] Open
Abstract
The type VI secretion system (T6SS) secretes antibacterial effectors into target competitors. Salmonella spp. encode five phylogenetically distinct T6SSs. Here, we characterize the function of the SPI-22 T6SS of Salmonella bongori showing that it has antibacterial activity and identify a group of antibacterial T6SS effectors (TseV1-4) containing an N-terminal PAAR-like domain and a C-terminal VRR-Nuc domain encoded next to cognate immunity proteins with a DUF3396 domain (TsiV1-4). TseV2 and TseV3 are toxic when expressed in Escherichia coli and bacterial competition assays confirm that TseV2 and TseV3 are secreted by the SPI-22 T6SS. Phylogenetic analysis reveals that TseV1-4 are evolutionarily related to enzymes involved in DNA repair. TseV3 recognizes specific DNA structures and preferentially cleave splayed arms, generating DNA double-strand breaks and inducing the SOS response in target cells. The crystal structure of the TseV3:TsiV3 complex reveals that the immunity protein likely blocks the effector interaction with the DNA substrate. These results expand our knowledge on the function of Salmonella pathogenicity islands, the evolution of toxins used in biological conflicts, and the endogenous mechanisms regulating the activity of these toxins.
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Affiliation(s)
- Julia Takuno Hespanhol
- Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São PauloSão PauloBrazil
| | | | | | - Liam Mead
- Department of Biosciences, University of BirminghamBirminghamUnited Kingdom
| | - Edgar Enrique Llontop
- Departamento de Bioquímica, Instituto de Química, Universidade de São PauloSão PauloBrazil
| | - Gustavo Chagas-Santos
- Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São PauloSão PauloBrazil
| | - Chuck Shaker Farah
- Departamento de Bioquímica, Instituto de Química, Universidade de São PauloSão PauloBrazil
| | - Robson Francisco de Souza
- Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São PauloSão PauloBrazil
| | - Rodrigo da Silva Galhardo
- Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São PauloSão PauloBrazil
| | - Andrew L Lovering
- Department of Biosciences, University of BirminghamBirminghamUnited Kingdom
| | - Ethel Bayer-Santos
- Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São PauloSão PauloBrazil
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15
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Carobbi A, Di Nepi S, Fridman CM, Dar Y, Ben‐Yaakov R, Barash I, Salomon D, Sessa G. An antibacterial T6SS in Pantoea agglomerans pv. betae delivers a lysozyme-like effector to antagonize competitors. Environ Microbiol 2022; 24:4787-4802. [PMID: 35706135 PMCID: PMC9796082 DOI: 10.1111/1462-2920.16100] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Accepted: 06/10/2022] [Indexed: 12/30/2022]
Abstract
The type VI secretion system (T6SS) is deployed by numerous Gram-negative bacteria to deliver toxic effectors into neighbouring cells. The genome of Pantoea agglomerans pv. betae (Pab) phytopathogenic bacteria contains a gene cluster (T6SS1) predicted to encode a complete T6SS. Using secretion and competition assays, we found that T6SS1 in Pab is a functional antibacterial system that allows this pathogen to outcompete rival plant-associated bacteria found in its natural environment. Computational analysis of the T6SS1 gene cluster revealed that antibacterial effector and immunity proteins are encoded within three genomic islands that also harbour arrays of orphan immunity genes or toxin and immunity cassettes. Functional analyses indicated that VgrG, a specialized antibacterial effector, contains a C-terminal catalytically active glucosaminidase domain that is used to degrade prey peptidoglycan. Moreover, we confirmed that a bicistronic unit at the end of the T6SS1 cluster encodes a novel antibacterial T6SS effector and immunity pair. Together, these results demonstrate that Pab T6SS1 is an antibacterial system delivering a lysozyme-like effector to eliminate competitors, and indicate that this bacterium contains additional novel T6SS effectors.
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Affiliation(s)
- Andrea Carobbi
- School of Plant Sciences and Food Security, The George S. Wise Faculty of Life SciencesTel‐Aviv UniversityTel‐Aviv
| | - Simone Di Nepi
- School of Plant Sciences and Food Security, The George S. Wise Faculty of Life SciencesTel‐Aviv UniversityTel‐Aviv
| | - Chaya M. Fridman
- Department of Clinical Microbiology and Immunology, Sackler Faculty of MedicineTel Aviv UniversityTel Aviv
| | - Yasmin Dar
- Department of Clinical Microbiology and Immunology, Sackler Faculty of MedicineTel Aviv UniversityTel Aviv
| | - Rotem Ben‐Yaakov
- Department of Clinical Microbiology and Immunology, Sackler Faculty of MedicineTel Aviv UniversityTel Aviv
| | - Isaac Barash
- School of Plant Sciences and Food Security, The George S. Wise Faculty of Life SciencesTel‐Aviv UniversityTel‐Aviv
| | - Dor Salomon
- Department of Clinical Microbiology and Immunology, Sackler Faculty of MedicineTel Aviv UniversityTel Aviv
| | - Guido Sessa
- School of Plant Sciences and Food Security, The George S. Wise Faculty of Life SciencesTel‐Aviv UniversityTel‐Aviv
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16
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Lorente Cobo N, Sibinelli-Sousa S, Biboy J, Vollmer W, Bayer-Santos E, Prehna G. Molecular characterization of the type VI secretion system effector Tlde1a reveals a structurally altered LD-transpeptidase fold. J Biol Chem 2022; 298:102556. [PMID: 36183829 PMCID: PMC9638812 DOI: 10.1016/j.jbc.2022.102556] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Revised: 09/26/2022] [Accepted: 09/27/2022] [Indexed: 12/01/2022] Open
Abstract
The type VI secretion system (T6SS) is a molecular machine that Gram-negative bacteria have adapted for multiple functions, including interbacterial competition. Bacteria use the T6SS to deliver protein effectors into adjacent cells to kill rivals and establish niche dominance. Central to T6SS-mediated bacterial competition is an arms race to acquire diverse effectors to attack and neutralize target cells. The peptidoglycan has a central role in bacterial cell physiology, and effectors that biochemically modify peptidoglycan structure effectively induce cell death. One such T6SS effector is Tlde1a from Salmonella Typhimurium. Tlde1a functions as an LD-carboxypeptidase to cleave tetrapeptide stems and as an LD-transpeptidase to exchange the terminal D-alanine of a tetrapeptide stem with a noncanonical D-amino acid. To understand how Tlde1a exhibits toxicity at the molecular level, we determined the X-ray crystal structure of Tlde1a alone and in complex with D-amino acids. Our structural data revealed that Tlde1a possesses a unique LD-transpeptidase fold consisting of a dual pocket active site with a capping subdomain. This includes an exchange pocket to bind a D-amino acid for exchange and a catalytic pocket to position the D-alanine of a tetrapeptide stem for cleavage. Our toxicity assays in Escherichia coli and in vitro peptidoglycan biochemical assays with Tlde1a variants correlate Tlde1a molecular features directly to its biochemical functions. We observe that the LD-carboxypeptidase and LD-transpeptidase activities of Tlde1a are both structurally and functionally linked. Overall, our data highlight how an LD-transpeptidase fold has been structurally altered to create a toxic effector in the T6SS arms race.
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Affiliation(s)
- Neil Lorente Cobo
- Department of Microbiology, University of Manitoba, Winnipeg, Canada
| | - Stephanie Sibinelli-Sousa
- Department of Microbiology, Biomedical Sciences Institute, University of São Paulo, São Paulo, Brazil
| | - Jacob Biboy
- Centre for Bacterial Cell Biology, Biosciences Institute, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Waldemar Vollmer
- Centre for Bacterial Cell Biology, Biosciences Institute, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Ethel Bayer-Santos
- Department of Microbiology, Biomedical Sciences Institute, University of São Paulo, São Paulo, Brazil
| | - Gerd Prehna
- Department of Microbiology, University of Manitoba, Winnipeg, Canada.
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17
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A Quorum Sensing-Regulated Type VI Secretion System Containing Multiple Nonredundant VgrG Proteins Is Required for Interbacterial Competition in Chromobacterium violaceum. Microbiol Spectr 2022; 10:e0157622. [PMID: 35876575 PMCID: PMC9430734 DOI: 10.1128/spectrum.01576-22] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The environmental pathogenic bacterium Chromobacterium violaceum kills Gram-positive bacteria by delivering violacein packed into outer membrane vesicles, but nothing is known about its contact-dependent competition mechanisms. In this work, we demonstrate that C. violaceum utilizes a type VI secretion system (T6SS) containing multiple VgrG proteins primarily for interbacterial competition. The single T6SS of C. violaceum contains six vgrG genes, which are located in the main T6SS cluster and four vgrG islands. Using T6SS core component-null mutant strains, Western blotting, fluorescence microscopy, and competition assays, we showed that the C. violaceum T6SS is active and required for competition against Gram-negative bacteria such as Pseudomonas aeruginosa but dispensable for C. violaceum infection in mice. Characterization of single and multiple vgrG mutants revealed that, despite having high sequence similarity, the six VgrGs show little functional redundancy, with VgrG3 showing a major role in T6SS function. Our coimmunoprecipitation data support a model of VgrG3 interacting directly with the other VgrGs. Moreover, we determined that the promoter activities of T6SS genes increased at high cell density, but the produced Hcp protein was not secreted under such condition. This T6SS growth phase-dependent regulation was dependent on CviR but not on CviI, the components of a C. violaceum quorum sensing (QS) system. Indeed, a ΔcviR but not a ΔcviI mutant was completely defective in Hcp secretion, T6SS activity, and interbacterial competition. Overall, our data reveal that C. violaceum relies on a QS-regulated T6SS to outcompete other bacteria and expand our knowledge about the redundancy of multiple VgrGs. IMPORTANCE The type VI secretion system (T6SS) is a contractile nanomachine used by many Gram-negative bacteria to inject toxic effectors into adjacent cells. The delivered effectors are bound to the components of a puncturing apparatus containing the protein VgrG. The T6SS has been implicated in pathogenesis and, more commonly, in competition among bacteria. Chromobacterium violaceum is an environmental bacterium that causes deadly infections in humans. In this work, we characterized the single T6SS of C. violaceum ATCC 12472, including its six VgrG proteins, regarding its function and regulation. This previously undescribed C. violaceum T6SS is active, regulated by QS, and required for interbacterial competition instead of acute infection in mice. Among the VgrGs, VgrG3, encoded outside the main T6SS cluster, showed a major contribution to T6SS function. These results shed light on a key contact-dependent killing mechanism used by C. violaceum to antagonize other bacteria.
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18
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Li W, Liu X, Tsui W, Xu A, Li D, Zhang X, Li P, Bian X, Zhang J. Identification and Comparative Genomic Analysis of Type VI Secretion Systems and Effectors in Klebsiella pneumoniae. Front Microbiol 2022; 13:853744. [PMID: 35633723 PMCID: PMC9134191 DOI: 10.3389/fmicb.2022.853744] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Accepted: 04/14/2022] [Indexed: 01/26/2023] Open
Abstract
Klebsiella pneumoniae is a nosocomial opportunistic pathogen that can cause pneumonia, liver abscesses, and infections of the bloodstream. The resistance and pathogenicity of K. pneumoniae pose major challenges to clinical practice. However, the ecology and pathogenic mechanisms of K. pneumoniae have not been fully elucidated. Among these mechanisms, the secretion systems encoded by strains of the bacteria confer adaptive advantages depending on the niche occupied. The type VI secretion system (T6SS) is a multi-protein complex that delivers effector proteins to the extracellular environment or directly to eukaryotic or prokaryotic cells. T6SSs are widely distributed in Gram-negative bacteria and play an important role in bacterial virulence and the interactions between bacteria and other microorganisms or the environment. This study aimed to enhance the understanding of the characteristics of T6SSs in K. pneumoniae through an in-depth comparative genomic analysis of the T6SS in 241 sequenced strains of K. pneumoniae. We identified the T6SS loci, the synteny of the loci in different species, as well as the effectors and core T6SS-related genes in K. pneumoniae. The presence of a T6SS was a common occurrence in K. pneumoniae, and two T6SS clusters are the most prevalent. The variable region downstream of the gene vgrG usually encodes effector proteins. Conserved domain analysis indicated that the identified putative effectors in K. pneumoniae had the functions of lipase, ribonuclease, deoxyribonuclease, and polysaccharide hydrolase. However, some effectors did not contain predicted functional domains, and their specific functions have yet to be elucidated. This in silico study represents a detailed analysis of T6SS-associated genes in K. pneumoniae and provides a foundation for future studies on the mechanism(s) of T6SSs, especially effectors, which may generate new insights into pathogenicity and lead to the identification of proteins with novel antimicrobial properties.
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Affiliation(s)
- Wanzhen Li
- Institute of Antibiotics, Huashan Hospital, Fudan University, Shanghai, China
- Key Laboratory of Clinical Pharmacology of Antibiotics, Shanghai, China
- National Health Commission and National Clinical Research Center for Aging and Medicine, Huashan Hospital, Fudan University, Shanghai, China
| | - Xiaofen Liu
- Institute of Antibiotics, Huashan Hospital, Fudan University, Shanghai, China
- Key Laboratory of Clinical Pharmacology of Antibiotics, Shanghai, China
- National Health Commission and National Clinical Research Center for Aging and Medicine, Huashan Hospital, Fudan University, Shanghai, China
| | - Waitang Tsui
- State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, Department of Biochemistry, School of Life Sciences, Fudan University, Shanghai, China
| | - An Xu
- Institute of Antibiotics, Huashan Hospital, Fudan University, Shanghai, China
| | - Dan Li
- Institute of Antibiotics, Huashan Hospital, Fudan University, Shanghai, China
| | - Xuefei Zhang
- Institute of Antibiotics, Huashan Hospital, Fudan University, Shanghai, China
| | - Pei Li
- Institute of Antibiotics, Huashan Hospital, Fudan University, Shanghai, China
| | - Xingchen Bian
- Institute of Antibiotics, Huashan Hospital, Fudan University, Shanghai, China
- Key Laboratory of Clinical Pharmacology of Antibiotics, Shanghai, China
- National Health Commission and National Clinical Research Center for Aging and Medicine, Huashan Hospital, Fudan University, Shanghai, China
| | - Jing Zhang
- Institute of Antibiotics, Huashan Hospital, Fudan University, Shanghai, China
- Key Laboratory of Clinical Pharmacology of Antibiotics, Shanghai, China
- National Health Commission and National Clinical Research Center for Aging and Medicine, Huashan Hospital, Fudan University, Shanghai, China
- Phase I Unit, Huashan Hospital, Fudan University, Shanghai, China
- *Correspondence: Jing Zhang,
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19
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Unni R, Pintor KL, Diepold A, Unterweger D. Presence and absence of type VI secretion systems in bacteria. MICROBIOLOGY (READING, ENGLAND) 2022; 168. [PMID: 35467500 DOI: 10.1099/mic.0.001151] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The type VI secretion system (T6SS) is a molecular puncturing device that enables Gram-negative bacteria to kill competitors, manipulate host cells and take up nutrients. Who would want to miss such superpowers? Indeed, many studies show how widespread the secretion apparatus is among microbes. However, it is becoming evident that, on multiple taxonomic levels, from phyla to species and strains, some bacteria lack a T6SS. Here, we review who does and does not have a type VI secretion apparatus and speculate on the dynamic process of gaining and losing the secretion system to better understand its spread and distribution across the microbial world.
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Affiliation(s)
- Rahul Unni
- Max Planck Institute for Evolutionary Biology, August-Thienemann-Straße 2, 24306 Plön, Germany.,Institute for Experimental Medicine, Kiel University, Michaelisstraße 5, 24105 Kiel, Germany
| | - Katherine L Pintor
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Karl-von-Frisch-Str. 10, 35043 Marburg, Germany
| | - Andreas Diepold
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Karl-von-Frisch-Str. 10, 35043 Marburg, Germany
| | - Daniel Unterweger
- Max Planck Institute for Evolutionary Biology, August-Thienemann-Straße 2, 24306 Plön, Germany.,Institute for Experimental Medicine, Kiel University, Michaelisstraße 5, 24105 Kiel, Germany
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20
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Liyanapathiranage P, Wagner N, Avram O, Pupko T, Potnis N. Phylogenetic Distribution and Evolution of Type VI Secretion System in the Genus Xanthomonas. Front Microbiol 2022; 13:840308. [PMID: 35495725 PMCID: PMC9048695 DOI: 10.3389/fmicb.2022.840308] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Accepted: 02/10/2022] [Indexed: 11/13/2022] Open
Abstract
The type VI secretion system (T6SS) present in many Gram-negative bacteria is a contact-dependent apparatus that can directly deliver secreted effectors or toxins into diverse neighboring cellular targets including both prokaryotic and eukaryotic organisms. Recent reverse genetics studies with T6 core gene loci have indicated the importance of functional T6SS toward overall competitive fitness in various pathogenic Xanthomonas spp. To understand the contribution of T6SS toward ecology and evolution of Xanthomonas spp., we explored the distribution of the three distinguishable T6SS clusters, i3*, i3***, and i4, in approximately 1,740 Xanthomonas genomes, along with their conservation, genetic organization, and their evolutionary patterns in this genus. Screening genomes for core genes of each T6 cluster indicated that 40% of the sequenced strains possess two T6 clusters, with combinations of i3*** and i3* or i3*** and i4. A few strains of Xanthomonas citri, Xanthomonas phaseoli, and Xanthomonas cissicola were the exception, possessing a unique combination of i3* and i4. The findings also indicated clade-specific distribution of T6SS clusters. Phylogenetic analysis demonstrated that T6SS clusters i3* and i3*** were probably acquired by the ancestor of the genus Xanthomonas, followed by gain or loss of individual clusters upon diversification into subsequent clades. T6 i4 cluster has been acquired in recent independent events by group 2 xanthomonads followed by its spread via horizontal dissemination across distinct clades across groups 1 and 2 xanthomonads. We also noted reshuffling of the entire core T6 loci, as well as T6SS spike complex components, hcp and vgrG, among different species. Our findings indicate that gain or loss events of specific T6SS clusters across Xanthomonas phylogeny have not been random.
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Affiliation(s)
| | - Naama Wagner
- The Shmunis School of Biomedicine and Cancer Research, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Oren Avram
- The Shmunis School of Biomedicine and Cancer Research, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Tal Pupko
- The Shmunis School of Biomedicine and Cancer Research, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Neha Potnis
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL, United States
- *Correspondence: Neha Potnis,
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21
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Nie H, Xiao Y, Song M, Wu N, Peng Q, Duan W, Chen W, Huang Q. Wsp system oppositely modulates antibacterial activity and biofilm formation via FleQ-FleN complex in Pseudomonas putida. Environ Microbiol 2022; 24:1543-1559. [PMID: 35178858 DOI: 10.1111/1462-2920.15905] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Accepted: 01/13/2022] [Indexed: 11/29/2022]
Abstract
Type VI secretion systems (T6SS) are specific antibacterial weapons employed by diverse bacteria to protect themselves from competitors. Pseudomonas putida KT2440 possesses a functional T6SS (K1-T6SS) and exhibits antibacterial activity towards a broad range of bacteria. Here we found that the Wsp signal transduction system regulated K1-T6SS expression via synthesizing the second messenger cyclic di-GMP (c-di-GMP), thus mediating antibacterial activity in P. putida. High-level c-di-GMP produced by Wsp system repressed the transcription of K1-T6SS genes in structural operon and vgrG1 operon. Transcriptional regulator FleQ and ATPase FleN functioned as repressors in the Wsp system-modulated K1-T6SS transcription. However, FleQ and FleN functioned as activators in biofilm formation, and Wsp system promoted biofilm formation largely in a FleQ/FleN-dependent manner. Furthermore, FleQ-FleN complex bound directly to the promoter of K1-T6SS structural operon in vitro, and c-di-GMP promoted the binding. Besides, P. putida biofilm cells showed higher c-di-GMP levels and lower antibacterial activity than planktonic cells. Overall, our findings reveal a mechanism by which Wsp system oppositely modulates antibacterial activity and biofilm formation via FleQ-FleN, and demonstrate the relationship between plankton/biofilm lifestyles and antibacterial activity in P. putida.
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Affiliation(s)
- Hailing Nie
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, 430070, China
| | - Yujie Xiao
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, 430070, China
| | - Miaomiao Song
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, 430070, China
| | - Nianqi Wu
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, 430070, China
| | - Qi Peng
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, 430070, China
| | - Wei Duan
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, 430070, China
| | - Wenli Chen
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, 430070, China
| | - Qiaoyun Huang
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, 430070, China.,Hubei Key Laboratory of Soil Environment and Pollution Remediation, College of Resources and Environment, Huazhong Agricultural University, Wuhan, 430070, China
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22
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Xu J, Ericson CF, Lien YW, Rutaganira FUN, Eisenstein F, Feldmüller M, King N, Pilhofer M. Identification and structure of an extracellular contractile injection system from the marine bacterium Algoriphagus machipongonensis. Nat Microbiol 2022; 7:397-410. [PMID: 35165385 PMCID: PMC8894135 DOI: 10.1038/s41564-022-01059-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Accepted: 01/05/2022] [Indexed: 12/11/2022]
Abstract
Contractile injection systems (CISs) are phage tail-like nanomachines, mediating bacterial cell–cell interactions as either type VI secretion systems (T6SSs) or extracellular CISs (eCISs). Bioinformatic studies uncovered a phylogenetic group of hundreds of putative CIS gene clusters that are highly diverse and widespread; however, only four systems have been characterized. Here we studied a putative CIS gene cluster in the marine bacterium Algoriphagus machipongonensis. Using an integrative approach, we show that the system is compatible with an eCIS mode of action. Our cryo-electron microscopy structure revealed several features that differ from those seen in other CISs: a ‘cap adaptor’ located at the distal end, a ‘plug’ exposed to the tube lumen, and a ‘cage’ formed by massive extensions of the baseplate. These elements are conserved in other CISs, and our genetic tools identified that they are required for assembly, cargo loading and function. Furthermore, our atomic model highlights specific evolutionary hotspots and will serve as a framework for understanding and re−engineering CISs. The characterization of an extracellular contractile injection system (eCIS) from the marine bacterium Algoriphagus machipongonensis (AlgoCIS) reveals structural features linked to the assembly and function of this nanomachine.
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23
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Tall tails: cryo-electron microscopy of phage tail DNA ejection conduits. Biochem Soc Trans 2022; 50:459-22W. [PMID: 35129586 PMCID: PMC9022992 DOI: 10.1042/bst20210799] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Revised: 01/06/2022] [Accepted: 01/12/2022] [Indexed: 11/17/2022]
Abstract
The majority of phages, viruses that infect prokaryotes, inject their genomic material into their host through a tubular assembly known as a tail. Despite the genomic diversity of tailed phages, only three morphological archetypes have been described: contractile tails of Myoviridae-like phages; short non-contractile tails of Podoviridae-like phages; and long and flexible non-contractile tails of Siphoviridae-like phages. While early cryo-electron microscopy (cryo-EM) work elucidated the organisation of the syringe-like injection mechanism of contractile tails, the intrinsic flexibility of the long non-contractile tails prevented high-resolution structural determination. In 2020, four cryo-EM structures of Siphoviridae-like tail tubes were solved and revealed common themes and divergences. The central tube is structurally conserved and homologous to the hexameric rings of the tail tube protein (TTP) also found in contractile tails, bacterial pyocins, and type VI secretion systems. The interior surface of the tube presents analogous motifs of negatively charged amino acids proposed to facilitate ratcheting of the DNA during genome ejection. The lack of a conformational change upon genome ejection implicates the tape measure protein in triggering genome release. A distinctive feature of Siphoviridae-like tails is their flexibility. This results from loose inter-ring connections that can asymmetrically stretch on one side to allow bending and flexing of the tube without breaking. The outer surface of the tube differs greatly and may be smooth or rugged due to additional Ig-like domains in TTP. Some of these variable domains may contribute to adsorption of the phage to prokaryotic and eukaryotic cell surfaces affecting tropism and virulence.
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24
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Kitao T, Kubori T, Nagai H. Recent advances in structural studies of the Legionella pneumophila Dot/Icm type IV secretion system. Microbiol Immunol 2021; 66:67-74. [PMID: 34807482 PMCID: PMC9302130 DOI: 10.1111/1348-0421.12951] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Accepted: 11/15/2021] [Indexed: 11/29/2022]
Abstract
The intracellular bacterial pathogen Legionella pneumophila utilizes the Dot/Icm type IV secretion system to translocate approximately 300 effector proteins to establish a replicative niche known as the Legionella‐containing vacuole. The Dot/Icm system is classified as a type IVB secretion system, which is evolutionarily closely related to the I‐type conjugation systems and is distinct from type IVA secretion systems, such as the Agrobacterium VirB/D4 system. Although both type IVA and IVB systems directly transport nucleic acids or proteins into the cytosol of recipient cells, the components and architecture of type IVB systems are much more complex than those of type IVA systems. Taking full advantage of rapidly developing cryo‐electron microscopy techniques, the structural details of the transport apparatus and coupling complexes in the Dot/Icm system have been clarified in the past few years. In this review, we summarize recent progress in the structural studies of the L. pneumophila type IVB secretion system and the insights gained into the mechanisms of substrate recognition and transport.
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Affiliation(s)
- Tomoe Kitao
- Department of Microbiology, Graduate School of Medicine, Gifu University, Gifu, Gifu, 501-1194, Japan
| | - Tomoko Kubori
- Department of Microbiology, Graduate School of Medicine, Gifu University, Gifu, Gifu, 501-1194, Japan.,G-CHAIN, Gifu University, Gifu, Gifu, 501-1194, Japan
| | - Hiroki Nagai
- Department of Microbiology, Graduate School of Medicine, Gifu University, Gifu, Gifu, 501-1194, Japan.,G-CHAIN, Gifu University, Gifu, Gifu, 501-1194, Japan
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Abstract
Legionella pneumophila, the causative agent of Legionnaires' disease, is a facultative intracellular pathogen that survives inside phagocytic host cells by establishing a protected replication niche, termed the "Legionella-containing vacuole" (LCV). To form an LCV and subvert pivotal host pathways, L. pneumophila employs a type IV secretion system (T4SS), which translocates more than 300 different effector proteins into the host cell. The L. pneumophila T4SS complex has been shown to span the bacterial cell envelope at the bacterial poles. However, the interactions between the T4SS and the LCV membrane are not understood. Using cryo-focused ion beam milling, cryo-electron tomography, and confocal laser scanning fluorescence microscopy, we show that up to half of the intravacuolar L. pneumophila bacteria tether their cell pole to the LCV membrane. Tethering coincides with the presence and function of T4SSs and likely promotes the establishment of distinct contact sites between T4SSs and the LCV membrane. Contact sites are characterized by indentations in the limiting LCV membrane and localize juxtaposed to T4SS machineries. The data are in agreement with the notion that effector translocation occurs by close membrane contact rather than by an extended pilus. Our findings provide novel insights into the interactions of the L. pneumophila T4SS with the LCV membrane in situ. IMPORTANCE Legionnaires' disease is a life-threatening pneumonia, which is characterized by high fever, coughing, shortness of breath, muscle pain, and headache. The disease is caused by the amoeba-resistant bacterium L. pneumophila found in various soil and aquatic environments and is transmitted to humans via the inhalation of small bacteria-containing droplets. An essential virulence factor of L. pneumophila is a so-called "type IV secretion system" (T4SS), which, by injecting a plethora of "effector proteins" into the host cell, determines pathogen-host interactions and the formation of a distinct intracellular compartment, the "Legionella-containing vacuole" (LCV). It is unknown how the T4SS makes contact to the LCV membrane to deliver the effectors. In this study, we identify indentations in the host cell membrane in close proximity to functional T4SSs localizing at the bacterial poles. Our work reveals first insights into the architecture of Legionella-LCV contact sites.
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Sibinelli-Sousa S, de Araújo-Silva AL, Hespanhol JT, Bayer-Santos E. Revisiting the steps of Salmonella gut infection with a focus on antagonistic interbacterial interactions. FEBS J 2021; 289:4192-4211. [PMID: 34546626 DOI: 10.1111/febs.16211] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Revised: 09/12/2021] [Accepted: 09/20/2021] [Indexed: 12/20/2022]
Abstract
A commensal microbial community is established in the mammalian gut during its development, and these organisms protect the host against pathogenic invaders. The hallmark of noninvasive Salmonella gut infection is the induction of inflammation via effector proteins secreted by the type III secretion system, which modulate host responses to create a new niche in which the pathogen can overcome the colonization resistance imposed by the microbiota. Several studies have shown that endogenous microbes are important to control Salmonella infection by competing for resources. However, there is limited information about antimicrobial mechanisms used by commensals and pathogens during these in vivo disputes for niche control. This review aims to revisit the steps that Salmonella needs to overcome during gut colonization-before and after the induction of inflammation-to achieve an effective infection. We focus on a series of reported and hypothetical antagonistic interbacterial interactions in which both contact-independent and contact-dependent mechanisms might define the outcome of the infection.
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Affiliation(s)
| | | | - Julia Takuno Hespanhol
- Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, Brazil
| | - Ethel Bayer-Santos
- Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, Brazil
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27
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Differential Cellular Response to Translocated Toxic Effectors and Physical Penetration by the Type VI Secretion System. Cell Rep 2021; 31:107766. [PMID: 32553162 DOI: 10.1016/j.celrep.2020.107766] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 04/28/2020] [Accepted: 05/21/2020] [Indexed: 01/06/2023] Open
Abstract
The type VI secretion system (T6SS) is a lethal microbial weapon that injects a large needle-like structure carrying toxic effectors into recipient cells through physical penetration. How recipients respond to physical force and effectors remains elusive. Here, we use a series of effector mutants of Vibrio cholerae to determine how T6SS elicits response in Pseudomonas aeruginosa and Escherichia coli. We show that TseL, but no other effectors or physical puncture, triggers the tit-for-tat response of P. aeruginosa H1-T6SS. Although E. coli is sensitive to all periplasmically expressed effectors, P. aeruginosa is most sensitive to TseL alone. We identify a number of stress response pathways that confer protection against TseL. Physical puncture of T6SS has a moderate inhibitory effect only on envelope-impaired tolB and rseA mutants. Our data reveal that recipient cells primarily respond to effector toxicity but not to physical contact, and they rely on the stress response for immunity-independent protection.
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28
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Abstract
The type VI secretion system (T6SS) is a bacterial nanoscale weapon that delivers toxins into prey ranging from bacteria and fungi to animal hosts. The cytosolic contractile sheath of the system wraps around stacked hexameric rings of Hcp proteins, which form an inner tube. At the tip of this tube is a puncturing device comprising a trimeric VgrG topped by a monomeric PAAR protein. The number of toxins a single system delivers per firing event remains unknown, since effectors can be loaded on diverse sites of the T6SS apparatus, notably the inner tube and the puncturing device. Each VgrG or PAAR can bind one effector, and additional effector cargoes can be carried in the Hcp ring lumen. While many VgrG- and PAAR-bound toxins have been characterized, to date, very few Hcp-bound effectors are known. Here, we used 3 known Pseudomonas aeruginosa Hcp proteins (Hcp1 to -3), each of which associates with one of the three T6SSs in this organism (H1-T6SS, H2-T6SS, and H3-T6SS), to perform in vivo pulldown assays. We confirmed the known interactions of Hcp1 with Tse1 to -4, further copurified a Hcp1-Tse4 complex, and identified potential novel Hcp1-bound effectors. Moreover, we demonstrated that Hcp2 and Hcp3 can shuttle T6SS cargoes toxic to Escherichia coli. Finally, we used a Tse1-Bla chimera to probe the loading strategy for Hcp passengers and found that while large effectors can be loaded onto Hcp, the formed complex jams the system, abrogating T6SS function.
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29
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Wang N, Han N, Tian R, Chen J, Gao X, Wu Z, Liu Y, Huang L. Role of the Type VI Secretion System in the Pathogenicity of Pseudomonas syringae pv. actinidiae, the Causative Agent of Kiwifruit Bacterial Canker. Front Microbiol 2021; 12:627785. [PMID: 33679650 PMCID: PMC7933208 DOI: 10.3389/fmicb.2021.627785] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Accepted: 01/29/2021] [Indexed: 02/03/2023] Open
Abstract
The type VI secretion system (T6SS), a macromolecular machine, plays an important role in the pathogenicity of many Gram-negative bacteria. However, the role of T6SS in the pathogenicity of Pseudomonas syringae pv. actinidiae (Psa), the pathogen of kiwifruit bacterial canker, is yet to be studied. Here, we found a T6SS gene cluster consisting of 13 core genes (A-J) in the genome of Psa M228 based on a genome-wide analysis. To determine whether the T6SS gene cluster affects the pathogenicity of Psa M228, T6SS and its 13 core gene deletion mutants were constructed and their pathogenicity was determined. The deletion mutants showed different degrees of reduction in pathogenicity compared with the wild-type strain M228; in tssM and tssJ mutants, pathogenicity was significantly reduced by 78.7 and 71.3%, respectively. The pathogenicity results were also confirmed by electron microscopy. To further confirm that the reduction in pathogenicity is related to the function of T6SS, we selected the T6SS gene cluster, comprising tssM and tssJ, for further analyses. Western blot results revealed that tssM and tssJ were necessary for hemolytic co-regulatory protein secretion, indicating that they encode a functional T6SS. Further, we explored the mechanism by which T6SS affects the pathogenicity of Psa M228. The ability of bacterial competition, biofilm formation, hydrogen peroxide tolerance, and proteolytic activity were all weakened in the deletion mutants M228ΔT6SS, M228ΔtssM, and M228ΔtssJ. All these properties of the two gene complementation mutants were restored to the same levels as those of the wild-type strain, M228. Quantitative real-time results showed that during the interaction between the deletion mutant M228ΔT6SS and the host, expression levels of T3SS transcriptional regulatory gene hrpR, structural genes hrpZ, hrcC, hopP1, and effector genes hopH1 and hopM1 were down-regulated at different levels. Taken together, our data provide evidence for the first time that the T6SS plays an important role in the pathogenicity of Psa, probably via effects on bacterial competition, biofilm formation, and environmental adaptability. Moreover, a complicated relationship exists between T6SS and T3SS.
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Affiliation(s)
- Nana Wang
- State Key Laboratory of Crop Stress Biology for Arid Areas, Northwest A&F University, Yangling, China.,College of Life Science, Northwest A&F University, Yangling, China
| | - Ning Han
- State Key Laboratory of Crop Stress Biology for Arid Areas, Northwest A&F University, Yangling, China.,College of Plant Protection, Northwest A&F University, Yangling, China
| | - Runze Tian
- State Key Laboratory of Crop Stress Biology for Arid Areas, Northwest A&F University, Yangling, China.,College of Plant Protection, Northwest A&F University, Yangling, China
| | - Jiliang Chen
- State Key Laboratory of Crop Stress Biology for Arid Areas, Northwest A&F University, Yangling, China.,College of Plant Protection, Northwest A&F University, Yangling, China
| | - Xiaoning Gao
- Institute of Bioengineering, Guangdong Academy of Sciences, Guangzhou, China
| | - Zhiran Wu
- State Key Laboratory of Crop Stress Biology for Arid Areas, Northwest A&F University, Yangling, China.,College of Plant Protection, Northwest A&F University, Yangling, China
| | - Yuqi Liu
- State Key Laboratory of Crop Stress Biology for Arid Areas, Northwest A&F University, Yangling, China.,College of Life Science, Northwest A&F University, Yangling, China
| | - Lili Huang
- State Key Laboratory of Crop Stress Biology for Arid Areas, Northwest A&F University, Yangling, China.,College of Plant Protection, Northwest A&F University, Yangling, China
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30
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Smith WPJ, Brodmann M, Unterweger D, Davit Y, Comstock LE, Basler M, Foster KR. The evolution of tit-for-tat in bacteria via the type VI secretion system. Nat Commun 2020; 11:5395. [PMID: 33106492 PMCID: PMC7589516 DOI: 10.1038/s41467-020-19017-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Accepted: 09/22/2020] [Indexed: 02/06/2023] Open
Abstract
Tit-for-tat is a familiar principle from animal behavior: individuals respond in kind to being helped or harmed by others. Remarkably some bacteria appear to display tit-for-tat behavior, but how this evolved is not understood. Here we combine evolutionary game theory with agent-based modelling of bacterial tit-for-tat, whereby cells stab rivals with poisoned needles (the type VI secretion system) after being stabbed themselves. Our modelling shows tit-for-tat retaliation is a surprisingly poor evolutionary strategy, because tit-for-tat cells lack the first-strike advantage of preemptive attackers. However, if cells retaliate strongly and fire back multiple times, we find that reciprocation is highly effective. We test our predictions by competing Pseudomonas aeruginosa (a tit-for-tat species) with Vibrio cholerae (random-firing), revealing that P. aeruginosa does indeed fire multiple times per incoming attack. Our work suggests bacterial competition has led to a particular form of reciprocation, where the principle is that of strong retaliation, or 'tits-for-tat'.
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Affiliation(s)
- William P J Smith
- Department of Zoology, University of Oxford, Oxford, OX1 3SZ, UK.
- Department of Biochemistry, University of Oxford, Oxford, OX1 3QU, UK.
| | - Maj Brodmann
- Biozentrum, University of Basel, Klingelbergstrasse 50/70, CH-4056, Basel, Switzerland
| | - Daniel Unterweger
- Institute for Experimental Medicine, Kiel University, 24105, Kiel, Germany
- Max-Planck Institute for Evolutionary Biology, 24306, Plön, Germany
| | - Yohan Davit
- Institut de Mécanique des Fluides de Toulouse, CNRS and Université de Toulouse, 31400, Toulouse, France
| | - Laurie E Comstock
- Division of Infectious Diseases, Brigham and Women's Hospital, Boston, MA, 02115, USA
| | - Marek Basler
- Biozentrum, University of Basel, Klingelbergstrasse 50/70, CH-4056, Basel, Switzerland
| | - Kevin R Foster
- Department of Zoology, University of Oxford, Oxford, OX1 3SZ, UK.
- Department of Biochemistry, University of Oxford, Oxford, OX1 3QU, UK.
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31
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Monjarás Feria J, Valvano MA. An Overview of Anti-Eukaryotic T6SS Effectors. Front Cell Infect Microbiol 2020; 10:584751. [PMID: 33194822 PMCID: PMC7641602 DOI: 10.3389/fcimb.2020.584751] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2020] [Accepted: 09/22/2020] [Indexed: 12/24/2022] Open
Abstract
The type VI secretion system (T6SS) is a transmembrane multiprotein nanomachine employed by many Gram-negative bacterial species to translocate, in a contact-dependent manner, effector proteins into adjacent prokaryotic or eukaryotic cells. Typically, the T6SS gene cluster encodes at least 13 conserved core components for the apparatus assembly and other less conserved accessory proteins and effectors. It functions as a contractile tail machine comprising a TssB/C sheath and an expelled puncturing device consisting of an Hcp tube topped by a spike complex of VgrG and PAAR proteins. Contraction of the sheath propels the tube out of the bacterial cell into a target cell and leads to the injection of toxic proteins. Different bacteria use the T6SS for specific roles according to the niche and versatility of the organism. Effectors are present both as cargo (by non-covalent interactions with one of the core components) or specialized domains (fused to structural components). Although several anti-prokaryotic effectors T6SSs have been studied, recent studies have led to a substantial increase in the number of characterized anti-eukaryotic effectors. Against eukaryotic cells, the T6SS is involved in modifying and manipulating diverse cellular processes that allows bacteria to colonize, survive and disseminate, including adhesion modification, stimulating internalization, cytoskeletal rearrangements and evasion of host innate immune responses.
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Affiliation(s)
| | - Miguel A. Valvano
- Wellcome-Wolfson Institute for Experimental Medicine, Queen's University Belfast, Belfast, United Kingdom
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32
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Structural Characterization of TssL from Acinetobacter baumannii: a Key Component of the Type VI Secretion System. J Bacteriol 2020; 202:JB.00210-20. [PMID: 32571965 DOI: 10.1128/jb.00210-20] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2020] [Accepted: 06/12/2020] [Indexed: 02/06/2023] Open
Abstract
The type VI secretion system (T6SS) is a complex molecular nanomachine used by Gram-negative bacteria to deliver diverse effectors into adjacent cells. A membrane complex (MC) anchors this transport system to the bacterial cell wall. One of the proteins forming the MC is TssL, a cytoplasmic protein bound to the inner membrane through a single transmembrane helix. Here, we report the structure of the cytoplasmic N-terminal region of TssL from Acinetobacter baumannii, a bacterium encoding in a single locus a secretion system that is a special case among other T6SSs. The protein structure, consisting of two antiparallel alpha-helical bundles connected by a short loop, reveals several interesting particularities compared with homologous proteins from other organisms. In addition, we demonstrate the structural significance of residues Asp98 and Glu99, which are strongly conserved among T6SS-encoding Gram-negative bacteria. Mutations in these two residues strongly impact protein dynamics, expression, and functionality. Our results improve our understanding of the T6SS of A. baumannii, which remains largely understudied compared with that of other pathogens.IMPORTANCE Several Acinetobacter species carry one functional type VI secretion system (T6SS). The T6SS is encoded in a single locus containing 16 conserved genes, most of which code for proteins essential to T6SS activity. One of these key components is TssL, a cytoplasmic protein bound to the inner membrane. Despite its importance and its particular characteristics, the structure of T6SS in A. baumannii remains understudied. Here, we present structural, in silico, and in vivo studies of TssL, highlighting the importance of two well-conserved residues and improving our understanding of this secretion system in this bacterium.
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Kochanowsky RM, Bradshaw C, Forlastro I, Stock SP. Xenorhabdus bovienii strain jolietti uses a type 6 secretion system to kill closely related Xenorhabdus strains. FEMS Microbiol Ecol 2020; 96:fiaa073. [PMID: 32558899 PMCID: PMC7353953 DOI: 10.1093/femsec/fiaa073] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Accepted: 04/21/2020] [Indexed: 01/25/2023] Open
Abstract
Xenorhabdus bovienii strain jolietti (XBJ) is a Gram-negative bacterium that interacts with several organisms as a part of its life cycle. It is a beneficial symbiont of nematodes, a potent pathogen of a wide range of soil-dwelling insects and also has the ability to kill soil- and insect-associated microbes. Entomopathogenic Steinernema nematodes vector XBJ into insects, releasing the bacteria into the insect body cavity. There, XBJ produce a variety of insecticidal toxins and antimicrobials. XBJ's genome also encodes two separate Type Six Secretion Systems (T6SSs), structures that allow bacteria to inject specific proteins directly into other cells, but their roles in the XBJ life cycle are mostly unknown. To probe the function of these T6SSs, we generated mutant strains lacking the key structural protein Hcp from each T6SS and assessed phenotypes related to different parts of XBJ's life cycle. Here we demonstrate that one of the T6SSs is more highly expressed in in vitro growth conditions and has antibacterial activity against other Xenorhabdus strains, and that the two T6SSs have a redundant role in biofilm formation.
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Affiliation(s)
- Rebecca M Kochanowsky
- School of Animal and Comparative Biomedical Sciences, University of Arizona, 1117 E. Lowell St., Tucson, AZ 85721, USA
- Center for Insect Science, University of Arizona, 1007 E. Lowell St., Tucson, AZ 85721, USA
| | - Christine Bradshaw
- School of Animal and Comparative Biomedical Sciences, University of Arizona, 1117 E. Lowell St., Tucson, AZ 85721, USA
| | - Isabel Forlastro
- School of Animal and Comparative Biomedical Sciences, University of Arizona, 1117 E. Lowell St., Tucson, AZ 85721, USA
| | - S Patricia Stock
- School of Animal and Comparative Biomedical Sciences, University of Arizona, 1117 E. Lowell St., Tucson, AZ 85721, USA
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Hernandez RE, Gallegos‐Monterrosa R, Coulthurst SJ. Type
VI
secretion system effector proteins: Effective weapons for bacterial competitiveness. Cell Microbiol 2020; 22:e13241. [DOI: 10.1111/cmi.13241] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 06/08/2020] [Accepted: 06/15/2020] [Indexed: 12/31/2022]
Affiliation(s)
- Ruth E. Hernandez
- Division of Molecular Microbiology, School of Life SciencesUniversity of Dundee Dundee UK
| | | | - Sarah J. Coulthurst
- Division of Molecular Microbiology, School of Life SciencesUniversity of Dundee Dundee UK
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35
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A Family of T6SS Antibacterial Effectors Related to l,d-Transpeptidases Targets the Peptidoglycan. Cell Rep 2020; 31:107813. [DOI: 10.1016/j.celrep.2020.107813] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Revised: 04/20/2020] [Accepted: 06/03/2020] [Indexed: 12/17/2022] Open
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36
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The evolution of the type VI secretion system as a disintegration weapon. PLoS Biol 2020; 18:e3000720. [PMID: 32453732 PMCID: PMC7274471 DOI: 10.1371/journal.pbio.3000720] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 06/05/2020] [Accepted: 04/30/2020] [Indexed: 12/22/2022] Open
Abstract
The type VI secretion system (T6SS) is a nanomachine used by many bacteria to drive a toxin-laden needle into other bacterial cells. Although the potential to influence bacterial competition is clear, the fitness impacts of wielding a T6SS are not well understood. Here we present a new agent-based model that enables detailed study of the evolutionary costs and benefits of T6SS weaponry during competition with other bacteria. Our model identifies a key problem with the T6SS. Because of its short range, T6SS activity becomes self-limiting, as dead cells accumulate in its way, forming “corpse barriers” that block further attacks. However, further exploration with the model presented a solution to this problem: if injected toxins can quickly lyse target cells in addition to killing them, the T6SS becomes a much more effective weapon. We tested this prediction with single-cell analysis of combat between T6SS-wielding Acinetobacter baylyi and T6SS-sensitive Escherichia coli. As predicted, delivery of lytic toxins is highly effective, whereas nonlytic toxins leave large patches of E. coli alive. We then analyzed hundreds of bacterial species using published genomic data, which suggest that the great majority of T6SS-wielding species do indeed use lytic toxins, indicative of a general principle underlying weapon evolution. Our work suggests that, in the T6SS, bacteria have evolved a disintegration weapon whose effectiveness often rests upon the ability to break up competitors. Understanding the evolutionary function of bacterial weapons can help in the design of probiotics that can both establish well and eliminate problem species. Bacteria attack each other with poison-tipped spears. This study combines theory and experiments to show that these spears (Type VI Secretion Systems) have evolved to break their targets apart with lytic toxins, as this then clears the way to rapidly stab new victims.
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37
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Allsopp LP, Bernal P, Nolan LM, Filloux A. Causalities of war: The connection between type VI secretion system and microbiota. Cell Microbiol 2020; 22:e13153. [PMID: 31872954 PMCID: PMC7540082 DOI: 10.1111/cmi.13153] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2019] [Revised: 11/23/2019] [Accepted: 12/19/2019] [Indexed: 12/14/2022]
Abstract
Microbiota niches have space and/or nutrient restrictions, which has led to the coevolution of cooperation, specialisation, and competition within the population. Different animal and environmental niches contain defined resident microbiota that tend to be stable over time and offer protection against undesired intruders. Yet fluxes can occur, which alter the composition of a bacterial population. In humans, the microbiota are now considered a key contributor to maintenance of health and homeostasis, and its alteration leads to dysbiosis. The bacterial type VI secretion system (T6SS) transports proteins into the environment, directly into host cells or can function as an antibacterial weapon by killing surrounding competitors. Upon contact with neighbouring cells, the T6SS fires, delivering a payload of effector proteins. In the absence of an immunity protein, this results in growth inhibition or death of prey leading to a competitive advantage for the attacker. It is becoming apparent that the T6SS has a role in modulating and shaping the microbiota at multiple levels, which is the focus of this review. Discussed here is the T6SS, its role in competition, key examples of its effect upon the microbiota, and future avenues of research.
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Affiliation(s)
- Luke P Allsopp
- National Heart and Lung Institute, Imperial College London, London, UK
| | - Patricia Bernal
- Department of Biology, Faculty of Sciences, Universidad Autónoma de Madrid, Madrid, Spain
| | - Laura M Nolan
- National Heart and Lung Institute, Imperial College London, London, UK
| | - Alain Filloux
- Department of Life Sciences, MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, UK
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38
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Mariano G, Trunk K, Williams DJ, Monlezun L, Strahl H, Pitt SJ, Coulthurst SJ. A family of Type VI secretion system effector proteins that form ion-selective pores. Nat Commun 2019; 10:5484. [PMID: 31792213 PMCID: PMC6889166 DOI: 10.1038/s41467-019-13439-0] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Accepted: 11/05/2019] [Indexed: 12/25/2022] Open
Abstract
Type VI secretion systems (T6SSs) are nanomachines widely used by bacteria to deliver toxic effector proteins directly into neighbouring cells. However, the modes of action of many effectors remain unknown. Here we report that Ssp6, an anti-bacterial effector delivered by a T6SS of the opportunistic pathogen Serratia marcescens, is a toxin that forms ion-selective pores. Ssp6 inhibits bacterial growth by causing depolarisation of the inner membrane in intoxicated cells, together with increased outer membrane permeability. Reconstruction of Ssp6 activity in vitro demonstrates that it forms cation-selective pores. A survey of bacterial genomes reveals that genes encoding Ssp6-like effectors are widespread in Enterobacteriaceae and often linked with T6SS genes. We conclude that Ssp6 and similar proteins represent a new family of T6SS-delivered anti-bacterial effectors.
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Affiliation(s)
- Giuseppina Mariano
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dow St, Dundee, DD1 5EH, UK
| | - Katharina Trunk
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dow St, Dundee, DD1 5EH, UK
| | - David J Williams
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dow St, Dundee, DD1 5EH, UK
| | - Laura Monlezun
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dow St, Dundee, DD1 5EH, UK
| | - Henrik Strahl
- Centre for Bacterial Cell Biology, Newcastle University, Richardson Road, Newcastle-upon-Tyne, NE2 4AX, UK
| | - Samantha J Pitt
- School of Medicine, University of St Andrews, North Haugh, St Andrews, KY16 9TF, UK
| | - Sarah J Coulthurst
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dow St, Dundee, DD1 5EH, UK.
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Ziveri J, Chhuon C, Jamet A, Rytter H, Prigent G, Tros F, Barel M, Coureuil M, Lays C, Henry T, Keep NH, Guerrera IC, Charbit A. Critical Role of a Sheath Phosphorylation Site On the Assembly and Function of an Atypical Type VI Secretion System. Mol Cell Proteomics 2019; 18:2418-2432. [PMID: 31578219 PMCID: PMC6885697 DOI: 10.1074/mcp.ra119.001532] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Revised: 09/03/2019] [Indexed: 12/12/2022] Open
Abstract
The bacterial pathogen Francisella tularensis possesses a noncanonical type VI secretion system (T6SS) that is required for phagosomal escape in infected macrophages. KCl stimulation has been previously used to trigger assembly and secretion of the T6SS in culture. By differential proteomics, we found here that the amounts of the T6SS proteins remained unchanged upon KCl stimulation, suggesting involvement of post-translational modifications in T6SS assembly. A phosphoproteomic analysis indeed identified a unique phosphorylation site on IglB, a key component of the T6SS sheath. Substitutions of Y139 with alanine or phosphomimetics prevented T6SS formation and abolished phagosomal escape whereas substitution with phenylalanine delayed but did not abolish phagosomal escape in J774-1 macrophages. Altogether our data demonstrated that the Y139 site of IglB plays a critical role in T6SS biogenesis, suggesting that sheath phosphorylation could participate to T6SS dynamics.Data are available via ProteomeXchange with identifier PXD013619; and on MS-Viewer, key lkaqkllxwx.
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Affiliation(s)
- Jason Ziveri
- Université Paris Descartes, Sorbonne Paris Cité, INSERM U1151-CNRS UMR 8253, Institut Necker-Enfants Malades. Team 7: Pathogenesis of Systemic Infections, Paris 75015, France; Plateforme protéomique 3P5-Necker, Universit[c33c]zpi;● Paris Descartes - Structure Fédérative de Recherche Necker, INSERM US24/CNRS UMS3633, Paris 75015, France
| | - Cerina Chhuon
- Plateforme protéomique 3P5-Necker, Universit[c33c]zpi;● Paris Descartes - Structure Fédérative de Recherche Necker, INSERM US24/CNRS UMS3633, Paris 75015, France; Plateforme protéomique 3P5-Necker, Universit[c33c]zpi;● Paris Descartes - Structure Fédérative de Recherche Necker, INSERM US24/CNRS UMS3633, Paris 75015, France
| | - Anne Jamet
- Université Paris Descartes, Sorbonne Paris Cité, INSERM U1151-CNRS UMR 8253, Institut Necker-Enfants Malades. Team 7: Pathogenesis of Systemic Infections, Paris 75015, France; Plateforme protéomique 3P5-Necker, Universit[c33c]zpi;● Paris Descartes - Structure Fédérative de Recherche Necker, INSERM US24/CNRS UMS3633, Paris 75015, France
| | - Héloïse Rytter
- Université Paris Descartes, Sorbonne Paris Cité, INSERM U1151-CNRS UMR 8253, Institut Necker-Enfants Malades. Team 7: Pathogenesis of Systemic Infections, Paris 75015, France; Plateforme protéomique 3P5-Necker, Universit[c33c]zpi;● Paris Descartes - Structure Fédérative de Recherche Necker, INSERM US24/CNRS UMS3633, Paris 75015, France
| | - Guénolé Prigent
- Université Paris Descartes, Sorbonne Paris Cité, INSERM U1151-CNRS UMR 8253, Institut Necker-Enfants Malades. Team 7: Pathogenesis of Systemic Infections, Paris 75015, France; Plateforme protéomique 3P5-Necker, Universit[c33c]zpi;● Paris Descartes - Structure Fédérative de Recherche Necker, INSERM US24/CNRS UMS3633, Paris 75015, France
| | - Fabiola Tros
- Université Paris Descartes, Sorbonne Paris Cité, INSERM U1151-CNRS UMR 8253, Institut Necker-Enfants Malades. Team 7: Pathogenesis of Systemic Infections, Paris 75015, France; Plateforme protéomique 3P5-Necker, Universit[c33c]zpi;● Paris Descartes - Structure Fédérative de Recherche Necker, INSERM US24/CNRS UMS3633, Paris 75015, France
| | - Monique Barel
- Université Paris Descartes, Sorbonne Paris Cité, INSERM U1151-CNRS UMR 8253, Institut Necker-Enfants Malades. Team 7: Pathogenesis of Systemic Infections, Paris 75015, France; Plateforme protéomique 3P5-Necker, Universit[c33c]zpi;● Paris Descartes - Structure Fédérative de Recherche Necker, INSERM US24/CNRS UMS3633, Paris 75015, France
| | - Mathieu Coureuil
- Université Paris Descartes, Sorbonne Paris Cité, INSERM U1151-CNRS UMR 8253, Institut Necker-Enfants Malades. Team 7: Pathogenesis of Systemic Infections, Paris 75015, France; Plateforme protéomique 3P5-Necker, Universit[c33c]zpi;● Paris Descartes - Structure Fédérative de Recherche Necker, INSERM US24/CNRS UMS3633, Paris 75015, France
| | - Claire Lays
- CIRI, Centre International de Recherche en Infectiologie, Université Lyon, Inserm, U1111, University Claude Bernard Lyon 1, CNRS, UMR5308, École Normale Supérieure de Lyon, Labex ECOFECT, Eco-evolutionary dynamics of infectious diseases, F-69007, LYON, France
| | - Thomas Henry
- CIRI, Centre International de Recherche en Infectiologie, Université Lyon, Inserm, U1111, University Claude Bernard Lyon 1, CNRS, UMR5308, École Normale Supérieure de Lyon, Labex ECOFECT, Eco-evolutionary dynamics of infectious diseases, F-69007, LYON, France
| | - Nicholas H Keep
- Crystallography, Institute for Structural and Molecular Biology, Department of Biological Sciences Birkbeck, University of London, United Kingdom
| | - Ida Chiara Guerrera
- Plateforme protéomique 3P5-Necker, Universit[c33c]zpi;● Paris Descartes - Structure Fédérative de Recherche Necker, INSERM US24/CNRS UMS3633, Paris 75015, France; Plateforme protéomique 3P5-Necker, Universit[c33c]zpi;● Paris Descartes - Structure Fédérative de Recherche Necker, INSERM US24/CNRS UMS3633, Paris 75015, France.
| | - Alain Charbit
- Université Paris Descartes, Sorbonne Paris Cité, INSERM U1151-CNRS UMR 8253, Institut Necker-Enfants Malades. Team 7: Pathogenesis of Systemic Infections, Paris 75015, France; Plateforme protéomique 3P5-Necker, Universit[c33c]zpi;● Paris Descartes - Structure Fédérative de Recherche Necker, INSERM US24/CNRS UMS3633, Paris 75015, France.
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40
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Peñil-Celis A, Garcillán-Barcia MP. Crosstalk Between Type VI Secretion System and Mobile Genetic Elements. Front Mol Biosci 2019; 6:126. [PMID: 31799257 PMCID: PMC6863884 DOI: 10.3389/fmolb.2019.00126] [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: 09/23/2019] [Accepted: 10/28/2019] [Indexed: 12/11/2022] Open
Abstract
Many bacterial processes require cell-cell contacts. Such are the cases of bacterial conjugation, one of the main horizontal gene transfer mechanisms that physically spreads DNA, and the type VI secretion systems (T6SSs), which deploy antibacterial activity. Bacteria depend on conjugation to adapt to changing environments, while T6SS killing activity could pose a threat to mating partners. Here we review the experimental evidences of overlapping and interaction between the T6SSs, bacterial conjugation, and conjugative genetic elements.
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Affiliation(s)
- Arancha Peñil-Celis
- Instituto de Biomedicina y Biotecnología de Cantabria, Universidad de Cantabria-Consejo Superior de Investigaciones Científicas, Santander, Spain
| | - M Pilar Garcillán-Barcia
- Instituto de Biomedicina y Biotecnología de Cantabria, Universidad de Cantabria-Consejo Superior de Investigaciones Científicas, Santander, Spain
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41
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Jana B, Salomon D. Type VI secretion system: a modular toolkit for bacterial dominance. Future Microbiol 2019; 14:1451-1463. [DOI: 10.2217/fmb-2019-0194] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Bacteria use toxin delivery systems, such as the type VI secretion system (T6SS), to antagonize competitors. The T6SS transports toxins, called effectors, directly into recipient cells. In the absence of cognate immunity proteins that protect against kin-intoxication, these effectors target conserved and essential cell components resulting in growth arrest or cell death. Here, we focus on antibacterial T6SS effectors and explore their different activities, modes of delivery, and the domains and proteins that are associated with them to provide a modular and dynamic toxin arsenal. We conclude that these natural machines present a lucrative pool and platform for future antibacterial treatments.
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Affiliation(s)
- Biswanath Jana
- Department of Clinical Microbiology & Immunology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Dor Salomon
- Department of Clinical Microbiology & Immunology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv 6997801, Israel
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42
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A Mechanistic Perspective on PEX1 and PEX6, Two AAA+ Proteins of the Peroxisomal Protein Import Machinery. Int J Mol Sci 2019; 20:ijms20215246. [PMID: 31652724 PMCID: PMC6862443 DOI: 10.3390/ijms20215246] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Revised: 10/18/2019] [Accepted: 10/21/2019] [Indexed: 12/11/2022] Open
Abstract
In contrast to many protein translocases that use ATP or GTP hydrolysis as the driving force to transport proteins across biological membranes, the peroxisomal matrix protein import machinery relies on a regulated self-assembly mechanism for this purpose and uses ATP hydrolysis only to reset its components. The ATP-dependent protein complex in charge of resetting this machinery—the Receptor Export Module (REM)—comprises two members of the “ATPases Associated with diverse cellular Activities” (AAA+) family, PEX1 and PEX6, and a membrane protein that anchors the ATPases to the organelle membrane. In recent years, a large amount of data on the structure/function of the REM complex has become available. Here, we discuss the main findings and their mechanistic implications.
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43
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Lepore R, Kryshtafovych A, Alahuhta M, Veraszto HA, Bomble YJ, Bufton JC, Bullock AN, Caba C, Cao H, Davies OR, Desfosses A, Dunne M, Fidelis K, Goulding CW, Gurusaran M, Gutsche I, Harding CJ, Hartmann MD, Hayes CS, Joachimiak A, Leiman PG, Loppnau P, Lovering AL, Lunin VV, Michalska K, Mir-Sanchis I, Mitra AK, Moult J, Phillips GN, Pinkas DM, Rice PA, Tong Y, Topf M, Walton JD, Schwede T. Target highlights in CASP13: Experimental target structures through the eyes of their authors. Proteins 2019; 87:1037-1057. [PMID: 31442339 PMCID: PMC6851490 DOI: 10.1002/prot.25805] [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: 05/10/2019] [Revised: 08/09/2019] [Accepted: 08/19/2019] [Indexed: 01/10/2023]
Abstract
The functional and biological significance of selected CASP13 targets are described by the authors of the structures. The structural biologists discuss the most interesting structural features of the target proteins and assess whether these features were correctly reproduced in the predictions submitted to the CASP13 experiment.
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Affiliation(s)
- Rosalba Lepore
- BSC-CNS Barcelona Supercomputing Center, Barcelona, Spain
| | | | - Markus Alahuhta
- Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado
| | - Harshul A Veraszto
- Department of Protein Evolution, Max Planck Institute for Developmental Biology, Tübingen, Germany
| | - Yannick J Bomble
- Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado
| | - Joshua C Bufton
- Nuffield Department of Medicine; Structural Genomics Consortium, University of Oxford, Oxford, UK.,School of Biochemistry, University of Bristol, Bristol, UK
| | - Alex N Bullock
- Nuffield Department of Medicine; Structural Genomics Consortium, University of Oxford, Oxford, UK
| | - Cody Caba
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario, Canada
| | - Hongnan Cao
- Department of BioSciences, Rice University, Houston, Texas.,Great Lakes Bioenergy Research Center, University of Wisconsin, Madison, Wisconsin
| | - Owen R Davies
- Institute for Cell and Molecular Biosciences, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK
| | - Ambroise Desfosses
- School of Biological Sciences, University of Auckland, Auckland, New Zealand.,Institut de Biologie Structurale, Université Grenoble Alpes, CEA, CNRS, Grenoble, France
| | - Matthew Dunne
- Institute of Food, Nutrition and Health, Zurich, Switzerland
| | | | - Celia W Goulding
- Department of Molecular Biology and Biochemistry; Pharmaceutical Sciences, University of California Irvine, Irvine, California
| | - Manickam Gurusaran
- Institute for Cell and Molecular Biosciences, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK
| | - Irina Gutsche
- Institut de Biologie Structurale, Université Grenoble Alpes, CEA, CNRS, Grenoble, France
| | | | - Marcus D Hartmann
- Department of Protein Evolution, Max Planck Institute for Developmental Biology, Tübingen, Germany
| | - Christopher S Hayes
- Department of Molecular, Cellular and Developmental Biology, Biomolecular Science and Engineering Program, University of California, Santa Barbara, California
| | - Andrzej Joachimiak
- Structural Biology Center, Biosciences Division, Midwest Center for Structural Genomics, Argonne.,Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois
| | - Petr G Leiman
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, Texas
| | - Peter Loppnau
- Structural Genomics Consortium, University of Toronto, Toronto, Ontario, Canada
| | | | - Vladimir V Lunin
- Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado
| | - Karolina Michalska
- Structural Biology Center, Biosciences Division, Midwest Center for Structural Genomics, Argonne
| | - Ignacio Mir-Sanchis
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois
| | - A K Mitra
- School of Biological Sciences, University of Auckland, Auckland, New Zealand
| | - John Moult
- Institute for Bioscience and Biotechnology Research, Department of Cell Biology and Molecular genetics, University of Maryland, Rockville, Maryland, USA
| | - George N Phillips
- Department of BioSciences, Rice University, Houston, Texas.,Great Lakes Bioenergy Research Center, University of Wisconsin, Madison, Wisconsin
| | - Daniel M Pinkas
- Nuffield Department of Medicine; Structural Genomics Consortium, University of Oxford, Oxford, UK
| | - Phoebe A Rice
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois
| | - Yufeng Tong
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario, Canada.,Structural Genomics Consortium, University of Toronto, Toronto, Ontario, Canada
| | - Maya Topf
- Institute of Structural and Molecular Biology, Birkbeck, University College London, London, UK
| | - Jonathan D Walton
- Great Lakes Bioenergy Research Center and Department of Plant Biology, Michigan State University, East Lansing, Michigan
| | - Torsten Schwede
- Biozentrum University of Basel, Basel, Switzerland.,SIB Swiss Institute of Bioinformatics, Biozentrum University of Basel, Basel, Switzerland
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44
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Jana B, Fridman CM, Bosis E, Salomon D. A modular effector with a DNase domain and a marker for T6SS substrates. Nat Commun 2019; 10:3595. [PMID: 31399579 PMCID: PMC6688995 DOI: 10.1038/s41467-019-11546-6] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 07/16/2019] [Indexed: 12/30/2022] Open
Abstract
Bacteria deliver toxic effectors via type VI secretion systems (T6SSs) to dominate competitors, but the identity and function of many effectors remain unknown. Here we identify a Vibrio antibacterial T6SS effector that contains a previously undescribed, widespread DNase toxin domain that we call PoNe (Polymorphic Nuclease effector). PoNe belongs to a diverse superfamily of PD-(D/E)xK phosphodiesterases, and is associated with several toxin delivery systems including type V, type VI, and type VII. PoNe toxicity is antagonized by cognate immunity proteins (PoNi) containing DUF1911 and DUF1910 domains. In addition to PoNe, the effector contains a domain of unknown function (FIX domain) that is also found N-terminal to known toxin domains and is genetically and functionally linked to T6SS. FIX sequences can be used to identify T6SS effector candidates with potentially novel toxin domains. Our findings underline the modular nature of bacterial effectors harboring delivery or marker domains, specific to a secretion system, fused to interchangeable toxins. Bacteria deliver toxic effectors via type VI secretion systems (T6SSs) to dominate competitors. Here, the authors identify a Vibrio antibacterial effector that contains a new DNase toxin domain and a domain of unknown function that can be used as a marker to identify new T6SS effectors.
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Affiliation(s)
- Biswanath Jana
- Department of Clinical Microbiology and Immunology, Sackler Faculty of Medicine, Tel Aviv University, 6997801, Tel Aviv, Israel
| | - Chaya M Fridman
- Department of Clinical Microbiology and Immunology, Sackler Faculty of Medicine, Tel Aviv University, 6997801, Tel Aviv, Israel
| | - Eran Bosis
- Department of Biotechnology Engineering, ORT Braude College of Engineering, 2161002, Karmiel, Israel.
| | - Dor Salomon
- Department of Clinical Microbiology and Immunology, Sackler Faculty of Medicine, Tel Aviv University, 6997801, Tel Aviv, Israel.
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45
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Desfosses A, Venugopal H, Joshi T, Felix J, Jessop M, Jeong H, Hyun J, Heymann JB, Hurst MRH, Gutsche I, Mitra AK. Atomic structures of an entire contractile injection system in both the extended and contracted states. Nat Microbiol 2019; 4:1885-1894. [PMID: 31384001 PMCID: PMC6817355 DOI: 10.1038/s41564-019-0530-6] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Accepted: 07/02/2019] [Indexed: 02/07/2023]
Abstract
Contractile injection systems are sophisticated multiprotein nanomachines that puncture target cell membranes. While the amount of atomic resolution insights into contractile bacteriophage tails, bacterial type six secretion systems and R-pyocins is rapidly increasing, structural information about contraction of bacterial phage-like protein-translocation structures directed towards eukaryotic hosts is scarce. Here we characterise the antifeeding prophage AFP from Serratia entomophila by cryo-electron microscopy. We present the high-resolution structure of the entire AFP particle in the extended state, trace 11 protein chains de novo from the apical cap to the needle tip, describe localisation variants and perform specific structural comparisons with related systems. We analyse intersubunit interactions and highlight their universal conservation within contractile injection systems while revealing the specificities of AFP. Furthermore, we provide the structure of the AFP sheath-baseplate complex in a contracted state. This study reveals atomic details of interaction networks that accompany and define the contraction mechanism of toxin-delivery tailocins, offering a comprehensive framework for understanding their mode of action and for their possible adaptation as biocontrol agents.
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Affiliation(s)
- Ambroise Desfosses
- School of Biological Sciences, University of Auckland, Auckland, New Zealand.,Institut de Biologie Structurale (IBS), University Grenoble Alpes, CEA, CNRS, Grenoble, France
| | - Hariprasad Venugopal
- School of Biological Sciences, University of Auckland, Auckland, New Zealand.,Ramaciotti Centre for Cryo Electron Microscopy, Monash University, Melbourne, Victoria, Australia
| | - Tapan Joshi
- School of Biological Sciences, University of Auckland, Auckland, New Zealand
| | - Jan Felix
- Institut de Biologie Structurale (IBS), University Grenoble Alpes, CEA, CNRS, Grenoble, France
| | - Matthew Jessop
- School of Biological Sciences, University of Auckland, Auckland, New Zealand.,Institut de Biologie Structurale (IBS), University Grenoble Alpes, CEA, CNRS, Grenoble, France
| | - Hyengseop Jeong
- Electron Microscopy Research Center, Korea Basic Science Institute, Cheongju-si, Republic of Korea
| | - Jaekyung Hyun
- Electron Microscopy Research Center, Korea Basic Science Institute, Cheongju-si, Republic of Korea.,Molecular Cryo-Electron Microscopy Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| | - J Bernard Heymann
- Laboratory for Structural Biology Research, National Institute of Arthritis, Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Mark R H Hurst
- Forage Science, AgResearch, Lincoln Research Centre, Christchurch, New Zealand. .,Bio-Protection Research Centre, Christchurch, New Zealand.
| | - Irina Gutsche
- Institut de Biologie Structurale (IBS), University Grenoble Alpes, CEA, CNRS, Grenoble, France.
| | - Alok K Mitra
- School of Biological Sciences, University of Auckland, Auckland, New Zealand.
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46
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McCarthy RR, Yu M, Eilers K, Wang Y, Lai E, Filloux A. Cyclic di-GMP inactivates T6SS and T4SS activity in Agrobacterium tumefaciens. Mol Microbiol 2019; 112:632-648. [PMID: 31102484 PMCID: PMC6771610 DOI: 10.1111/mmi.14279] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/15/2019] [Indexed: 01/17/2023]
Abstract
The Type VI secretion system (T6SS) is a bacterial nanomachine that delivers effector proteins into prokaryotic and eukaryotic preys. This secretion system has emerged as a key player in regulating the microbial diversity in a population. In the plant pathogen Agrobacterium tumefaciens, the signalling cascades regulating the activity of this secretion system are poorly understood. Here, we outline how the universal eubacterial second messenger cyclic di-GMP impacts the production of T6SS toxins and T6SS structural components. We demonstrate that this has a significant impact on the ability of the phytopathogen to compete with other bacterial species in vitro and in planta. Our results suggest that, as opposed to other bacteria, c-di-GMP turns down the T6SS in A. tumefaciens thus impacting its ability to compete with other bacterial species within the rhizosphere. We also demonstrate that elevated levels of c-di-GMP within the cell decrease the activity of the Type IV secretion system (T4SS) and subsequently the capacity of A. tumefaciens to transform plant cells. We propose that such peculiar control reflects on c-di-GMP being a key second messenger that silences energy-costing systems during early colonization phase and biofilm formation, while low c-di-GMP levels unleash T6SS and T4SS to advance plant colonization.
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Affiliation(s)
- Ronan R. McCarthy
- MRC Centre for Molecular Bacteriology and Infection, Department of Life SciencesImperial College LondonLondonSW7 2AZUK
- Division of Biosciences, Department of Life SciencesCollege of Health and Life Sciences, Brunel University LondonUxbridgeUB8 3PHUK
| | - Manda Yu
- Institute of Plant and Microbial BiologyAcademia SinicaTaipei11529Taiwan
| | - Kira Eilers
- MRC Centre for Molecular Bacteriology and Infection, Department of Life SciencesImperial College LondonLondonSW7 2AZUK
| | - Yi‐Chieh Wang
- Institute of Plant and Microbial BiologyAcademia SinicaTaipei11529Taiwan
| | - Erh‐Min Lai
- Institute of Plant and Microbial BiologyAcademia SinicaTaipei11529Taiwan
| | - Alain Filloux
- MRC Centre for Molecular Bacteriology and Infection, Department of Life SciencesImperial College LondonLondonSW7 2AZUK
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Lennings J, Makhlouf M, Olejnik P, Mayer C, Brötz-Oesterhelt H, Schwarz S. Environmental and cellular factors affecting the localization of T6SS proteins in Burkholderia thailandensis. Int J Med Microbiol 2019; 309:151335. [PMID: 31378704 DOI: 10.1016/j.ijmm.2019.151335] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2019] [Revised: 07/15/2019] [Accepted: 07/17/2019] [Indexed: 01/22/2023] Open
Abstract
The type VI secretion system (T6SS) injects effector proteins into neighboring bacteria and host cells. Effector translocation is driven by contraction of a tubular sheath in the cytoplasm that expels an inner needle across the cell envelope. The AAA + ATPase ClpV disassembles and recycles the contracted sheath. While ClpV-1-GFP of the Burkholderia T6SS-1, which targets prokaryotic cells, assembles into randomly localized foci, ClpV-5-GFP of the virulence-associated T6SS-5 displays a polar distribution. The mechanisms underlying the localization of T6SSs to a particular site in the bacterial cell are currently unknown. We recently showed that ClpV-5-GFP retains its polar localization in the absence of all T6SS-5 components during infection of host cells. Herein, we set out to identify factors involved in the distribution of ClpV-5 and ClpV-1 in Burkholderia thailandensis. We show that focal assembly and polar localization of ClpV-5-GFP is not dependent on the intracellular host cell environment, known to contain the signal to induce T6SS-5 gene expression. In contrast to ClpV-5-GFP, localization of ClpV-1-GFP was dependent on the cognate T6SS. Foci formation of both ClpV5-GFP and ClpV-1-GFP was decreased by D cycloserine-mediated inhibition of peptidoglycan synthesis while treatment of B. thailandensis with A22 blocking the cytoskeletal protein MreB did not affect assembly of ClpV-5 and ClpV-1 into single discrete foci. Furthermore, we found that surface contact promotes but is not essential for localization of ClpV-5-GFP to the pole whereas expression of clpV-1-gfp appears to be induced by surface contact. In summary, the study provides novel insights into the localization of ClpV ATPases of T6SSs targeting prokaryotic and eukaryotic cells.
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Affiliation(s)
- Jan Lennings
- Interfaculty Institute of Microbiology and Infection Medicine, Department of Medical Microbiology and Hygiene, University of Tübingen, Tübingen, Germany
| | - Munira Makhlouf
- Interfaculty Institute of Microbiology and Infection Medicine, Department of Medical Microbiology and Hygiene, University of Tübingen, Tübingen, Germany
| | - Przemyslaw Olejnik
- Interfaculty Institute of Microbiology and Infection Medicine, Department of Medical Microbiology and Hygiene, University of Tübingen, Tübingen, Germany
| | - Christian Mayer
- Interfaculty Institute of Microbiology and Infection Medicine, Department of Microbial Bioactive Compounds, University of Tübingen, Tübingen, Germany
| | - Heike Brötz-Oesterhelt
- Interfaculty Institute of Microbiology and Infection Medicine, Department of Microbial Bioactive Compounds, University of Tübingen, Tübingen, Germany
| | - Sandra Schwarz
- Interfaculty Institute of Microbiology and Infection Medicine, Department of Medical Microbiology and Hygiene, University of Tübingen, Tübingen, Germany.
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48
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Bayer-Santos E, Ceseti LDM, Farah CS, Alvarez-Martinez CE. Distribution, Function and Regulation of Type 6 Secretion Systems of Xanthomonadales. Front Microbiol 2019; 10:1635. [PMID: 31379785 PMCID: PMC6653060 DOI: 10.3389/fmicb.2019.01635] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Accepted: 07/02/2019] [Indexed: 11/13/2022] Open
Abstract
Members of the Xanthomonadales order include several plant pathogens of significant economic and agricultural impact, such as Xanthomonas spp. Type 6 secretion systems (T6SSs) are contractile nanomachines used by many bacterial species to inject protein effectors into target prokaryotic and eukaryotic cells and provide a competitive advantage for bacteria in different environments. Effectors with antibacterial properties include peptidoglycan hydrolases, lipases and phospholipases that break down structural components of the cell envelope, promoting target-cell lysis; and RNases, DNAses, and NADases that affect target-cell metabolism, arresting growth. Effectors with anti-eukaryotic properties are functionally more diverse. The T6SS of Xanthomonas citri is the only example experimentally characterized so far within the Xanthomonadales order and displays anti-eukaryotic function by providing resistance to predation by amoeba. This T6SS is regulated at the transcriptional level by a signaling cascade involving a Ser/Thr kinase and an extracytoplasmic function (ECF) sigma factor. In this review, we performed in silico analyses of 35 genomes of Xanthomonadales and showed that T6SSs are widely distributed and phylogenetically classified into three major groups. In silico predictions identified a series of proteins with known toxic domains as putative T6SS effectors, suggesting that the T6SSs of Xanthomonadales display both anti-prokaryotic and anti-eukaryotic properties depending on the phylogenetic group and bacterial species.
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Affiliation(s)
- Ethel Bayer-Santos
- Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil
| | - Lucas de Moraes Ceseti
- Departamento de Genética, Evolução, Microbiologia e Imunologia, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, Brazil
| | - Chuck Shaker Farah
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil
| | - Cristina Elisa Alvarez-Martinez
- Departamento de Genética, Evolução, Microbiologia e Imunologia, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, Brazil
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Species-specific mechanisms of cytotoxicity toward immune cells determine the successful outcome of Vibrio infections. Proc Natl Acad Sci U S A 2019; 116:14238-14247. [PMID: 31221761 DOI: 10.1073/pnas.1905747116] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Vibrio species cause infectious diseases in humans and animals, but they can also live as commensals within their host tissues. How Vibrio subverts the host defenses to mount a successful infection remains poorly understood, and this knowledge is critical for predicting and managing disease. Here, we have investigated the cellular and molecular mechanisms underpinning infection and colonization of 2 virulent Vibrio species in an ecologically relevant host model, oyster, to study interactions with marine Vibrio species. All Vibrio strains were recognized by the immune system, but only nonvirulent strains were controlled. We showed that virulent strains were cytotoxic to hemocytes, oyster immune cells. By analyzing host and bacterial transcriptional responses to infection, together with Vibrio gene knock-outs, we discovered that Vibrio crassostreae and Vibrio tasmaniensis use distinct mechanisms to cause hemocyte lysis. Whereas V. crassostreae cytotoxicity is dependent on a direct contact with hemocytes and requires an ancestral gene encoding a protein of unknown function, r5.7, V. tasmaniensis cytotoxicity is dependent on phagocytosis and requires intracellular secretion of T6SS effectors. We conclude that proliferation of commensal vibrios is controlled by the host immune system, preventing systemic infections in oysters, whereas the successful infection of virulent strains relies on Vibrio species-specific molecular determinants that converge to compromise host immune cell function, allowing evasion of the host immune system.
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50
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Barbosa VAA, Lery LMS. Insights into Klebsiella pneumoniae type VI secretion system transcriptional regulation. BMC Genomics 2019; 20:506. [PMID: 31215404 PMCID: PMC6580597 DOI: 10.1186/s12864-019-5885-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2019] [Accepted: 06/05/2019] [Indexed: 12/21/2022] Open
Abstract
Background Klebsiella pneumoniae (KP) is an opportunistic pathogen that mainly causes respiratory and urinary tract infections. The frequent occurrence of simultaneously virulent and multiple drug-resistant isolates led WHO to include this species in the list of top priorities for research and development of therapeutic alternatives. The comprehensive knowledge of the molecular mechanisms underlying KP virulence may lead to the proposal of more efficient and specific drugs. One of its virulence factors is the Type VI Secretion System (T6SS), which contributes to bacterial competition, cell invasion and in vivo colonisation. Despite the few studies showing the involvement of T6SS in KP pathogenesis, little is known concerning the regulation of its expression. The understanding of regulatory mechanisms may give more clues about the function of the system and the possibilities of future interference in this process. This work aimed to standardise the annotation of T6SS genes in KP strains and identify mechanisms of their transcriptional regulation through computational predictions. Results We analyzed the genomes of Kp52.145, HS11286 and NTUH-K2044 strains to perform a broad prediction and re-annotation of T6SS genes through similarity searches, comparative and linear discriminant analysis. 38 genes were found in Kp52.145, while 29 in HS11286 and 30 in NTUH-K2044. Genes coding for iron uptake systems are encoded in adjacencies of T6SS, suggesting that KP T6SS might also play a role in ion import. Some of the T6SS genes are comprised in syntenic regions. 17 sigma 70-dependent promoter regions were identified in Kp52.145, 12 in HS11286 and 12 in NTUH-K2044. Using VirtualFootprint algorithm, binding sites for 13 transcriptional regulators were found in Kp52.145 and 9 in HS11286 and 17 in NTUH-K2044. Six of them are common to the 3 strains: OxyR, H-NS, RcsAB, GcvA, Fis, and OmpR. Conclusions The data presented herein are derived from computational analysis. Although future experimental studies are required to confirm those predictions, they suggest that KP T6SS might be regulated in response to environmental signals that are indeed sensed by the bacteria inside the human host: temperature (H-NS), nutrition-limitation (GcvA and Fis), oxidative stress (OxyR) and osmolarity (RscAB and OmpR). Electronic supplementary material The online version of this article (10.1186/s12864-019-5885-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Victor Augusto Araújo Barbosa
- Cellular Microbiology Laboratory, Oswaldo Cruz Foundation - Oswaldo Cruz Institute, Av. Brasil, 4365 - Manguinhos, Rio de Janeiro, RJ, CEP: 21040-900, Brazil
| | - Leticia Miranda Santos Lery
- Cellular Microbiology Laboratory, Oswaldo Cruz Foundation - Oswaldo Cruz Institute, Av. Brasil, 4365 - Manguinhos, Rio de Janeiro, RJ, CEP: 21040-900, Brazil.
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