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Klebsiella pneumoniae type VI secretion system-mediated microbial competition is PhoPQ controlled and reactive oxygen species dependent. PLoS Pathog 2020; 16:e1007969. [PMID: 32191774 PMCID: PMC7108748 DOI: 10.1371/journal.ppat.1007969] [Citation(s) in RCA: 74] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Revised: 03/31/2020] [Accepted: 02/17/2020] [Indexed: 12/21/2022] Open
Abstract
Klebsiella pneumoniae is recognized as an urgent threat to human health due to the increasing isolation of multidrug resistant strains. Hypervirulent strains are a major concern due to their ability to cause life-threating infections in healthy hosts. The type VI secretion system (T6SS) is widely implicated in microbial antagonism, and it mediates interactions with host eukaryotic cells in some cases. In silico search for genes orthologous to T6SS component genes and T6SS effector genes across 700 K. pneumoniae genomes shows extensive diversity in T6SS genes across the K. pneumoniae species. Temperature, oxygen tension, pH, osmolarity, iron levels, and NaCl regulate the expression of the T6SS encoded by a hypervirulent K. pneumoniae strain. Polymyxins and human defensin 3 also increase the activity of the T6SS. A screen for regulators governing T6SS uncover the correlation between the transcription of the T6SS and the ability to kill E. coli prey. Whereas H-NS represses the T6SS, PhoPQ, PmrAB, Hfq, Fur, RpoS and RpoN positively regulate the T6SS. K. pneumoniae T6SS mediates intra and inter species bacterial competition. This antagonism is only evident when the prey possesses an active T6SS. The PhoPQ two component system governs the activation of K. pneumoniae T6SS in bacterial competitions. Mechanistically, PhoQ periplasmic domain, and the acid patch within, is essential to activate K. pneumoniae T6SS. Klebsiella T6SS also mediates anti-fungal competition. We have delineated the contribution of each of the individual VgrGs in microbial competition and identified VgrG4 as a T6SS effector. The DUF2345 domain of VgrG4 is sufficient to intoxicate bacteria and yeast. ROS generation mediates the antibacterial effects of VgrG4, and the antitoxin Sel1E protects against the toxic activity of VgrG4. Our findings provide a better understanding of the regulation of the T6SS in bacterial competitions, and place ROS as an early event in microbial competition. Klebsiella pneumoniae has been singled out as an “urgent threat to human health” due to extremely drug resistant strains. Numerous studies investigate the molecular mechanisms underlying antibiotic resistance in K. pneumoniae, while others dissect the virulence strategies of this pathogen. However, there is still limited knowledge on the fitness of Klebsiella in the environment, and, particularly, the competition of Klebsiella with other species. Here, we demonstrate that Klebsiella exploits the type VI secretion system (T6SS) nanoweapon to kill bacterial competitors and fungi. K. pneumoniae perceives T6SS attacks from bacterial competitors, resulting in retaliation against the aggressive cell. The perception of the attack involved the sensor PhoPQ and led to the up-regulation of the T6SS. We identified one of the toxins deployed by the T6SS to antagonize other microbes and revealed how Klebsiella protects itself from this toxin. Our findings provide a better understanding of the T6SS role in microbial competition and uncover new aspects on how bacteria regulate T6SS-mediated microbial antagonism.
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52
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Repizo GD, Espariz M, Seravalle JL, Salcedo SP. Bioinformatic Analysis of the Type VI Secretion System and Its Potential Toxins in the Acinetobacter Genus. Front Microbiol 2019; 10:2519. [PMID: 31736933 PMCID: PMC6838775 DOI: 10.3389/fmicb.2019.02519] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Accepted: 10/18/2019] [Indexed: 12/14/2022] Open
Abstract
Several Acinetobacter strains are important nosocomial pathogens, with Acinetobacter baumannii as the species of greatest concern worldwide due to its multi-drug resistance and recent appearance of hyper-virulent strains in the clinical setting. Acinetobacter colonization of the environment and the host is associated with a multitude of factors which remain poorly characterized. Among them, the secretion systems (SS) encoded by Acinetobacter species confer adaptive advantages depending on the niche occupied. Different SS have been characterized in this group of microorganisms, including T6SS used by several Acinetobacter species to outcompete other bacteria and in some A. baumannii strains for Galleria mellonella colonization. Therefore, to better understand the distribution of the T6SS in this genus we carried out an in-depth comparative genomic analysis of the T6SS in 191 sequenced strains. To this end, we analyzed the gene content, sequence similarity, synteny and operon structure of each T6SS loci. The presence of a single conserved T6SS-main cluster (T6SS-1), with two different genetic organizations, was detected in the genomes of several ecologically diverse species. Furthermore, a second main cluster (T6SS-2) was detected in a subgroup of 3 species of environmental origin. Detailed analysis also showed an impressive genetic versatility in T6SS-associated islands, carrying VgrG, PAAR and putative toxin-encoding genes. This in silico study represents the first detailed intra-species comparative analysis of T6SS-associated genes in the Acinetobacter genus, that should contribute to the future experimental characterization of T6SS proteins and effectors.
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Affiliation(s)
- Guillermo D Repizo
- Departamento de Microbiologia, Facultad de Ciencias Bioquimicas y Farmaceuticas, Instituto de Biologia Molecular y Celular de Rosario (IBR, CONICET), Universidad Nacional de Rosario, Rosario, Argentina
| | - Martín Espariz
- Departamento de Microbiologia, Facultad de Ciencias Bioquimicas y Farmaceuticas, Instituto de Biologia Molecular y Celular de Rosario (IBR, CONICET), Universidad Nacional de Rosario, Rosario, Argentina
| | - Joana L Seravalle
- Departamento de Microbiologia, Facultad de Ciencias Bioquimicas y Farmaceuticas, Instituto de Biologia Molecular y Celular de Rosario (IBR, CONICET), Universidad Nacional de Rosario, Rosario, Argentina
| | - Suzana P Salcedo
- Laboratory of Molecular Microbiology and Structural Biochemistry, CNRS UMR 5086, University of Lyon, Lyon, France
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53
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Wang J, Brodmann M, Basler M. Assembly and Subcellular Localization of Bacterial Type VI Secretion Systems. Annu Rev Microbiol 2019; 73:621-638. [DOI: 10.1146/annurev-micro-020518-115420] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Bacteria need to deliver large molecules out of the cytosol to the extracellular space or even across membranes of neighboring cells to influence their environment, prevent predation, defeat competitors, or communicate. A variety of protein-secretion systems have evolved to make this process highly regulated and efficient. The type VI secretion system (T6SS) is one of the largest dynamic assemblies in gram-negative bacteria and allows for delivery of toxins into both bacterial and eukaryotic cells. The recent progress in structural biology and live-cell imaging shows the T6SS as a long contractile sheath assembled around a rigid tube with associated toxins anchored to a cell envelope by a baseplate and membrane complex. Rapid sheath contraction releases a large amount of energy used to push the tube and toxins through the membranes of neighboring target cells. Because reach of the T6SS is limited, some bacteria dynamically regulate its subcellular localization to precisely aim at their targets and thus increase efficiency of toxin translocation.
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Affiliation(s)
- Jing Wang
- Biozentrum, University of Basel, CH 4056 Basel, Switzerland
| | - Maj Brodmann
- Biozentrum, University of Basel, CH 4056 Basel, Switzerland
| | - Marek Basler
- Biozentrum, University of Basel, CH 4056 Basel, Switzerland
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54
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Bayer-Santos E, Cenens W, Matsuyama BY, Oka GU, Di Sessa G, Mininel IDV, Alves TL, Farah CS. The opportunistic pathogen Stenotrophomonas maltophilia utilizes a type IV secretion system for interbacterial killing. PLoS Pathog 2019; 15:e1007651. [PMID: 31513674 PMCID: PMC6759196 DOI: 10.1371/journal.ppat.1007651] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Revised: 09/24/2019] [Accepted: 08/09/2019] [Indexed: 12/11/2022] Open
Abstract
Bacterial type IV secretion systems (T4SS) are a highly diversified but evolutionarily related family of macromolecule transporters that can secrete proteins and DNA into the extracellular medium or into target cells. It was recently shown that a subtype of T4SS harboured by the plant pathogen Xanthomonas citri transfers toxins into target cells. Here, we show that a similar T4SS from the multi-drug-resistant opportunistic pathogen Stenotrophomonas maltophilia is proficient in killing competitor bacterial species. T4SS-dependent duelling between S. maltophilia and X. citri was observed by time-lapse fluorescence microscopy. A bioinformatic search of the S. maltophilia K279a genome for proteins containing a C-terminal domain conserved in X. citri T4SS effectors (XVIPCD) identified twelve putative effectors and their cognate immunity proteins. We selected a putative S. maltophilia effector with unknown function (Smlt3024) for further characterization and confirmed that it is indeed secreted in a T4SS-dependent manner. Expression of Smlt3024 in the periplasm of E. coli or its contact-dependent delivery via T4SS into E. coli by X. citri resulted in reduced growth rates, which could be counteracted by expression of its cognate inhibitor Smlt3025 in the target cell. Furthermore, expression of the VirD4 coupling protein of X. citri can restore the function of S. maltophilia ΔvirD4, demonstrating that effectors from one species can be recognized for transfer by T4SSs from another species. Interestingly, Smlt3024 is homologous to the N-terminal domain of large Ca2+-binding RTX proteins and the crystal structure of Smlt3025 revealed a topology similar to the iron-regulated protein FrpD from Neisseria meningitidis which has been shown to interact with the RTX protein FrpC. This work expands our current knowledge about the function of bacteria-killing T4SSs and increases the panel of effectors known to be involved in T4SS-mediated interbacterial competition, which possibly contribute to the establishment of S. maltophilia in clinical and environmental settings.
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Affiliation(s)
- Ethel Bayer-Santos
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, São Paulo, Brazil
- Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, São Paulo, Brazil
| | - William Cenens
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, São Paulo, Brazil
| | - Bruno Yasui Matsuyama
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, São Paulo, Brazil
| | - Gabriel Umaji Oka
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, São Paulo, Brazil
| | - Giancarlo Di Sessa
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, São Paulo, Brazil
| | - Izabel Del Valle Mininel
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, São Paulo, Brazil
| | - Tiago Lubiana Alves
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, São Paulo, Brazil
| | - Chuck Shaker Farah
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, São Paulo, Brazil
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55
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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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56
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Zeng C, Zou L. An account of in silico identification tools of secreted effector proteins in bacteria and future challenges. Brief Bioinform 2019; 20:110-129. [PMID: 28981574 DOI: 10.1093/bib/bbx078] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Indexed: 01/08/2023] Open
Abstract
Bacterial pathogens secrete numerous effector proteins via six secretion systems, type I to type VI secretion systems, to adapt to new environments or to promote virulence by bacterium-host interactions. Many computational approaches have been used in the identification of effector proteins before the subsequent experimental verification because they tolerate laborious biological procedures and are genome scale, automated and highly efficient. Prevalent examples include machine learning methods and statistical techniques. In this article, we summarize the computational progress toward predicting secreted effector proteins in bacteria, with an opening of an introduction of features that are used to discriminate effectors from non-effectors. The mechanism, contribution and deficiency of previous developed detection tools are presented, which are further benchmarked based on a curated testing data set. According to the results of benchmarking, potential improvements of the prediction performance are discussed, which include (1) more informative features for discriminating the effectors from non-effectors; (2) the construction of comprehensive training data set of the machine learning algorithms; (3) the advancement of reliable prediction methods and (4) a better interpretation of the mechanisms behind the molecular processes. The future of in silico identification of bacterial secreted effectors includes both opportunities and challenges.
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Affiliation(s)
- Cong Zeng
- Bioinformatics Center, Third Military Medical University (TMMU), China
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57
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Liebl D, Robert-Genthon M, Job V, Cogoni V, Attrée I. Baseplate Component TssK and Spatio-Temporal Assembly of T6SS in Pseudomonas aeruginosa. Front Microbiol 2019; 10:1615. [PMID: 31379775 PMCID: PMC6657622 DOI: 10.3389/fmicb.2019.01615] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Accepted: 06/28/2019] [Indexed: 11/22/2022] Open
Abstract
The Gram-negative bacteria use the contractile multi-molecular structure, called the Type VI Secretion System (T6SS) to inject toxic products into eukaryotic and prokaryotic cells. In this study, we use fluorescent protein fusions and time-lapse microscopy imaging to study the assembly dynamics of the baseplate protein TssK in Pseudomonas aeruginosa T6SS. TssK formed transient higher-order structures that correlated with dynamics of sheath component TssB. Assembly of peri-membrane TssK structures occurred de novo upon contact with competing bacteria. We show that this assembly required presence of TagQ-TagR envelope sensors, activity of PpkA kinase and anchoring to the inner membrane via TssM. Disassembly and repositioning of TssK component was dependent on PppA phosphatase and indispensable for repositioning and deployment of the entire contractile apparatus toward a new target cell. We also show that TssE is necessary for correct elongation and stability of TssB-sheath, but not for TssK assembly. Therefore, in P. aeruginosa, assembly of the TssK-containing structure relays on the post-translational regulatory envelope module and acts as spatio-temporal marker for further recruitment and subsequent assembly of the contractile apparatus.
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Affiliation(s)
- David Liebl
- Univ. Grenoble Alpes, CNRS, Bacterial Pathogenesis and Cellular Responses, ERL 5261, INSERM, UMR-S 1036, CEA, Grenoble, France
| | - Mylène Robert-Genthon
- Univ. Grenoble Alpes, CNRS, Bacterial Pathogenesis and Cellular Responses, ERL 5261, INSERM, UMR-S 1036, CEA, Grenoble, France
| | - Viviana Job
- Univ. Grenoble Alpes, CNRS, Bacterial Pathogenesis and Cellular Responses, ERL 5261, INSERM, UMR-S 1036, CEA, Grenoble, France.,Univ. Grenoble Alpes, CEA, CNRS, Institut de Biologie Structurale (IBS), Grenoble, France
| | - Valentina Cogoni
- Univ. Grenoble Alpes, CNRS, Bacterial Pathogenesis and Cellular Responses, ERL 5261, INSERM, UMR-S 1036, CEA, Grenoble, France
| | - Ina Attrée
- Univ. Grenoble Alpes, CNRS, Bacterial Pathogenesis and Cellular Responses, ERL 5261, INSERM, UMR-S 1036, CEA, Grenoble, France
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58
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Mariano G, Monlezun L, Coulthurst SJ. Dual Role for DsbA in Attacking and Targeted Bacterial Cells during Type VI Secretion System-Mediated Competition. Cell Rep 2019; 22:774-785. [PMID: 29346773 PMCID: PMC5792426 DOI: 10.1016/j.celrep.2017.12.075] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Revised: 12/15/2017] [Accepted: 12/21/2017] [Indexed: 01/23/2023] Open
Abstract
Incorporation of disulfide bonds into proteins can be critical for function or stability. In bacterial cells, the periplasmic enzyme DsbA is responsible for disulfide incorporation into many extra-cytoplasmic proteins. The type VI secretion system (T6SS) is a widely occurring nanomachine that delivers toxic effector proteins directly into rival bacterial cells, playing a key role in inter-bacterial competition. We report that two redundant DsbA proteins are required for virulence and for proper deployment of the T6SS in the opportunistic pathogen Serratia marcescens, with several T6SS components being subject to the action of DsbA in secreting cells. Importantly, we demonstrate that DsbA also plays a critical role in recipient target cells, being required for the toxicity of certain incoming effector proteins. Thus we reveal that target cell functions can be hijacked by T6SS effectors for effector activation, adding a further level of complexity to the T6SS-mediated inter-bacterial interactions which define varied microbial communities. Type VI secretion systems (T6SSs) are used by bacteria to attack competitors Disulfide bond formation by DsbA promotes assembly of an active T6SS in Serratia DsbA in the target cell is needed for activation of certain incoming T6SS effectors This work reveals that T6SS-delivered effectors can hijack target cell functions
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Affiliation(s)
- Giuseppina Mariano
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK
| | - Laura Monlezun
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK
| | - Sarah J Coulthurst
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK.
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Cherrak Y, Flaugnatti N, Durand E, Journet L, Cascales E. Structure and Activity of the Type VI Secretion System. Microbiol Spectr 2019; 7:10.1128/microbiolspec.psib-0031-2019. [PMID: 31298206 PMCID: PMC10957189 DOI: 10.1128/microbiolspec.psib-0031-2019] [Citation(s) in RCA: 79] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Indexed: 12/16/2022] Open
Abstract
The type VI secretion system (T6SS) is a multiprotein machine that uses a spring-like mechanism to inject effectors into target cells. The injection apparatus is composed of a baseplate on which is built a contractile tail tube/sheath complex. The inner tube, topped by the spike complex, is propelled outside of the cell by the contraction of the sheath. The injection system is anchored to the cell envelope and oriented towards the cell exterior by a trans-envelope complex. Effectors delivered by the T6SS are loaded within the inner tube or on the spike complex and can target prokaryotic and/or eukaryotic cells. Here we summarize the structure, assembly, and mechanism of action of the T6SS. We also review the function of effectors and their mode of recruitment and delivery.
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Affiliation(s)
- Yassine Cherrak
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie de la Méditerranée (IMM), Aix-Marseille Université, CNRS, UMR 7255, 13402 Marseille Cedex 20, France
- Y.C. and N.F. contributed equally to this review
| | - Nicolas Flaugnatti
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie de la Méditerranée (IMM), Aix-Marseille Université, CNRS, UMR 7255, 13402 Marseille Cedex 20, France
- Y.C. and N.F. contributed equally to this review
- Present address: Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Eric Durand
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie de la Méditerranée (IMM), Aix-Marseille Université, CNRS, UMR 7255, 13402 Marseille Cedex 20, France
| | - Laure Journet
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie de la Méditerranée (IMM), Aix-Marseille Université, CNRS, UMR 7255, 13402 Marseille Cedex 20, France
| | - Eric Cascales
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie de la Méditerranée (IMM), Aix-Marseille Université, CNRS, UMR 7255, 13402 Marseille Cedex 20, France
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60
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Role and Recruitment of the TagL Peptidoglycan-Binding Protein during Type VI Secretion System Biogenesis. J Bacteriol 2019; 201:JB.00173-19. [PMID: 30910811 DOI: 10.1128/jb.00173-19] [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: 03/04/2019] [Accepted: 03/19/2019] [Indexed: 12/29/2022] Open
Abstract
The type VI secretion system (T6SS) is an injection apparatus that uses a springlike mechanism for effector delivery. The contractile tail is composed of a needle tipped by a sharpened spike and wrapped by the sheath that polymerizes in an extended conformation on the assembly platform, or baseplate. Contraction of the sheath propels the needle and effectors associated with it into target cells. The passage of the needle through the cell envelope of the attacker is ensured by a dedicated trans-envelope channel complex. This membrane complex (MC) comprises the TssJ lipoprotein and the TssL and TssM inner membrane proteins. MC assembly is a hierarchized mechanism in which the different subunits are recruited in a specific order: TssJ, TssM, and then TssL. Once assembled, the MC serves as a docking station for the baseplate. In enteroaggregative Escherichia coli, the MC is accessorized by TagL, a peptidoglycan-binding (PGB) inner membrane-anchored protein. Here, we show that the PGB domain is the only functional domain of TagL and that the N-terminal transmembrane region mediates contact with the TssL transmembrane helix. Finally, we conduct fluorescence microscopy experiments to position TagL in the T6SS biogenesis pathway, demonstrating that TagL is recruited to the membrane complex downstream of TssL and is not required for baseplate docking.IMPORTANCE Bacteria use weapons to deliver effectors into target cells. One of these weapons, called the type VI secretion system (T6SS), could be compared to a nano-spear gun using a springlike mechanism for effector injection. By targeting bacteria and eukaryotic cells, the T6SS reshapes bacterial communities and hijacks host cell defenses. In enteroaggregative Escherichia coli, the T6SS is a multiprotein machine that comprises a cytoplasmic tail and a peptidoglycan-anchored trans-envelope channel. In this work, we show that TagL comprises an N-terminal domain that mediates contact with the channel and a peptidoglycan-binding domain that binds the cell wall. We then determine at which stage of T6SS biogenesis TagL is recruited and how TagL absence impacts the assembly pathway.
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61
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Coulthurst S. The Type VI secretion system: a versatile bacterial weapon. Microbiology (Reading) 2019; 165:503-515. [DOI: 10.1099/mic.0.000789] [Citation(s) in RCA: 114] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Affiliation(s)
- Sarah Coulthurst
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK
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62
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Abstract
The Type VI secretion system (T6SS) is a protein nanomachine that is widespread in Gram-negative bacteria and is used to translocate effector proteins directly into neighbouring cells. It represents a versatile bacterial weapon that can deliver effectors into distinct classes of target cells, playing key roles in inter-bacterial competition and bacterial interactions with eukaryotic cells. This versatility is underpinned by the ability of the T6SS to deliver a vast array of effector proteins, with many distinct activities and modes of interaction with the secretion machinery. Recent work has highlighted the importance and diversity of interactions mediated by T6SSs within polymicrobial communities, and offers new molecular insights into effector delivery and action in target cells.
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Affiliation(s)
- Sarah Coulthurst
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK
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63
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Zong B, Zhang Y, Wang X, Liu M, Zhang T, Zhu Y, Zheng Y, Hu L, Li P, Chen H, Tan C. Characterization of multiple type-VI secretion system (T6SS) VgrG proteins in the pathogenicity and antibacterial activity of porcine extra-intestinal pathogenic Escherichia coli. Virulence 2019; 10:118-132. [PMID: 30676217 PMCID: PMC6363058 DOI: 10.1080/21505594.2019.1573491] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Porcine extra-intestinal pathogenic Escherichia coli (ExPEC) causes great economic losses to the pig industry and poses a serious threat to public health worldwide. Some secreted virulence factors have been reported to be involved in the pathogenicity of the infection caused by ExPEC. Type-VI secretion system (T6SS) is discovered in many Gram-negative bacteria and contributes to the virulence of pathogenic bacteria. Valine-glycine repeat protein G (VgrG) has been reported as an important component of the functional T6SS. In our previous studies, a functional T6SS was identified in porcine ExPEC strain PCN033. Further analysis of the PCN033 genome identified two putative vgrGs genes (vgrG1 and 0248) located inside T6SS cluster and another two (vgrG2 and 1588) outside it. This study determined the function of the four putative VgrG proteins by constructing a series of mutants and complemented strains. In vitro, the VgrG1 protein was observed to be involved in the antibacterial ability and the interactions with cells. The animal model experiment showed that the deletion of vgrG1 significantly led to the decrease in the multiplication capacity of PCN033. However, the deletion of 0248 and/or the deletion of vgrG2 and 1588 had no effect on the pathogenicity of PCN033. The study of four putative VgrGs in PCN033 indicated that only VgrG1 plays an important role in the interaction between PCN033 and other bacteria or host cells. This study can provide a novel perspective to the pathogenesis of PCN033 and lay the foundation for discovering potential T6SS effectors.
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Affiliation(s)
- Bingbing Zong
- a State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine , Huazhong Agricultural University , Wuhan , Hubei , China.,b Key Laboratory of Preventive Veterinary Medicine in Hubei Province , The Cooperative Innovation Center for Sustainable Pig Production , Wuhan , Hubei , China.,c Key Laboratory of Development of Veterinary Diagnostic Products , Ministry of Agriculture of the People's Republic of China , Wuhan , Hubei , China.,d International Research Center for Animal Disease, Ministry of Science and Technology of the People's Republic of China , Wuhan , Hubei , China
| | - Yanyan Zhang
- a State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine , Huazhong Agricultural University , Wuhan , Hubei , China.,b Key Laboratory of Preventive Veterinary Medicine in Hubei Province , The Cooperative Innovation Center for Sustainable Pig Production , Wuhan , Hubei , China.,c Key Laboratory of Development of Veterinary Diagnostic Products , Ministry of Agriculture of the People's Republic of China , Wuhan , Hubei , China.,d International Research Center for Animal Disease, Ministry of Science and Technology of the People's Republic of China , Wuhan , Hubei , China
| | - Xiangru Wang
- a State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine , Huazhong Agricultural University , Wuhan , Hubei , China.,b Key Laboratory of Preventive Veterinary Medicine in Hubei Province , The Cooperative Innovation Center for Sustainable Pig Production , Wuhan , Hubei , China.,c Key Laboratory of Development of Veterinary Diagnostic Products , Ministry of Agriculture of the People's Republic of China , Wuhan , Hubei , China.,d International Research Center for Animal Disease, Ministry of Science and Technology of the People's Republic of China , Wuhan , Hubei , China
| | - Manli Liu
- e Hubei Biopesticide Engineering Research Centre , Hubei Academy of Agricultural Sciences , Wuhan Hubei , China
| | - Tongchao Zhang
- a State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine , Huazhong Agricultural University , Wuhan , Hubei , China.,b Key Laboratory of Preventive Veterinary Medicine in Hubei Province , The Cooperative Innovation Center for Sustainable Pig Production , Wuhan , Hubei , China.,c Key Laboratory of Development of Veterinary Diagnostic Products , Ministry of Agriculture of the People's Republic of China , Wuhan , Hubei , China.,d International Research Center for Animal Disease, Ministry of Science and Technology of the People's Republic of China , Wuhan , Hubei , China
| | - Yongwei Zhu
- a State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine , Huazhong Agricultural University , Wuhan , Hubei , China.,b Key Laboratory of Preventive Veterinary Medicine in Hubei Province , The Cooperative Innovation Center for Sustainable Pig Production , Wuhan , Hubei , China.,c Key Laboratory of Development of Veterinary Diagnostic Products , Ministry of Agriculture of the People's Republic of China , Wuhan , Hubei , China.,d International Research Center for Animal Disease, Ministry of Science and Technology of the People's Republic of China , Wuhan , Hubei , China
| | - Yucheng Zheng
- a State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine , Huazhong Agricultural University , Wuhan , Hubei , China.,b Key Laboratory of Preventive Veterinary Medicine in Hubei Province , The Cooperative Innovation Center for Sustainable Pig Production , Wuhan , Hubei , China.,c Key Laboratory of Development of Veterinary Diagnostic Products , Ministry of Agriculture of the People's Republic of China , Wuhan , Hubei , China.,d International Research Center for Animal Disease, Ministry of Science and Technology of the People's Republic of China , Wuhan , Hubei , China
| | - Linlin Hu
- a State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine , Huazhong Agricultural University , Wuhan , Hubei , China.,b Key Laboratory of Preventive Veterinary Medicine in Hubei Province , The Cooperative Innovation Center for Sustainable Pig Production , Wuhan , Hubei , China.,c Key Laboratory of Development of Veterinary Diagnostic Products , Ministry of Agriculture of the People's Republic of China , Wuhan , Hubei , China.,d International Research Center for Animal Disease, Ministry of Science and Technology of the People's Republic of China , Wuhan , Hubei , China
| | - Pei Li
- a State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine , Huazhong Agricultural University , Wuhan , Hubei , China.,b Key Laboratory of Preventive Veterinary Medicine in Hubei Province , The Cooperative Innovation Center for Sustainable Pig Production , Wuhan , Hubei , China.,c Key Laboratory of Development of Veterinary Diagnostic Products , Ministry of Agriculture of the People's Republic of China , Wuhan , Hubei , China.,d International Research Center for Animal Disease, Ministry of Science and Technology of the People's Republic of China , Wuhan , Hubei , China
| | - Huanchun Chen
- a State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine , Huazhong Agricultural University , Wuhan , Hubei , China.,b Key Laboratory of Preventive Veterinary Medicine in Hubei Province , The Cooperative Innovation Center for Sustainable Pig Production , Wuhan , Hubei , China.,c Key Laboratory of Development of Veterinary Diagnostic Products , Ministry of Agriculture of the People's Republic of China , Wuhan , Hubei , China.,d International Research Center for Animal Disease, Ministry of Science and Technology of the People's Republic of China , Wuhan , Hubei , China
| | - Chen Tan
- a State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine , Huazhong Agricultural University , Wuhan , Hubei , China.,b Key Laboratory of Preventive Veterinary Medicine in Hubei Province , The Cooperative Innovation Center for Sustainable Pig Production , Wuhan , Hubei , China.,c Key Laboratory of Development of Veterinary Diagnostic Products , Ministry of Agriculture of the People's Republic of China , Wuhan , Hubei , China.,d International Research Center for Animal Disease, Ministry of Science and Technology of the People's Republic of China , Wuhan , Hubei , China
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64
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Metzger LC, Matthey N, Stoudmann C, Collas EJ, Blokesch M. Ecological implications of gene regulation by TfoX and TfoY among diverse Vibrio species. Environ Microbiol 2019; 21:2231-2247. [PMID: 30761714 PMCID: PMC6618264 DOI: 10.1111/1462-2920.14562] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Revised: 01/16/2019] [Accepted: 02/10/2019] [Indexed: 01/26/2023]
Abstract
Bacteria of the genus Vibrio are common members of aquatic environments where they compete with other prokaryotes and defend themselves against grazing predators. A macromolecular protein complex called the type VI secretion system (T6SS) is used for both purposes. Previous research showed that the sole T6SS of the human pathogen V. cholerae is induced by extracellular (chitin) or intracellular (low c‐di‐GMP levels) cues and that these cues lead to distinctive signalling pathways for which the proteins TfoX and TfoY serve as master regulators. In this study, we tested whether the TfoX‐ and TfoY‐mediated regulation of T6SS, concomitantly with natural competence or motility, was conserved in non‐cholera Vibrio species, and if so, how these regulators affected the production of individual T6SSs in double‐armed vibrios. We show that, alongside representative competence genes, TfoX regulates at least one T6SS in all tested Vibrio species. TfoY, on the other hand, fostered motility in all vibrios but had a more versatile T6SS response in that it did not foster T6SS‐mediated killing in all tested vibrios. Collectively, our data provide evidence that the TfoX‐ and TfoY‐mediated signalling pathways are mostly conserved in diverse Vibrio species and important for signal‐specific T6SS induction.
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Affiliation(s)
- Lisa C Metzger
- Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Noémie Matthey
- Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Candice Stoudmann
- Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Esther J Collas
- Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Melanie Blokesch
- Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
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65
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Jiang X, Beust A, Sappa PK, Völker U, Dinse T, Herglotz J, Reinhold-Hurek B. Two Functionally Deviating Type 6 Secretion Systems Occur in the Nitrogen-Fixing Endophyte Azoarcus olearius BH72. Front Microbiol 2019; 10:459. [PMID: 30915056 PMCID: PMC6423157 DOI: 10.3389/fmicb.2019.00459] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Accepted: 02/21/2019] [Indexed: 12/18/2022] Open
Abstract
Type VI protein secretion systems (T6SSs) have been identified in many plant-associated bacteria. However, despite the fact that effector proteins may modulate host responses or interbacterial competition, only a few have been functionally dissected in detail. We dissected the T6SS in Azoarcus olearius strain BH72, a nitrogen-fixing model endophyte of grasses. The genome harbors two gene clusters encoding putative T6SSs, tss-1 and tss-2, of which only T6SS-2 shared genetic organization and functional homology with the H1-T6SS of Pseudomonas aeruginosa. While tss-2 genes were constitutively expressed, tss-1 genes were strongly up-regulated under conditions of nitrogen fixation. A comparative analysis of the wild type and mutants lacking either functional tss-1 or tss-2 allowed to differentiate the functions of both secretion systems. Abundance of Hcp in the culture supernatant as an indication for T6SS activity revealed that only T6SS-2 was active, either under aerobic or nitrogen-fixing conditions. Our data show that T6SS-2 but not T6SS-1 is post-translationally regulated by phosphorylation mediated by TagE/TagG (PpkA/PppA), and by the phosphorylation-independent inhibitory protein TagF, similar to published work in Pseudomonas. Therefore, T6SS-1 appears to be post-translationally regulated by yet unknown mechanisms. Thus, both T6SS systems appear to perform different functions in Azoarcus, one of them specifically adapted to the nitrogen-fixing lifestyle.
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Affiliation(s)
- Xun Jiang
- Department of Microbe-Plant Interactions, Faculty of Biology and Chemistry, Center for Biomolecular Interactions Bremen, University of Bremen, Bremen, Germany
| | - Andreas Beust
- Department of Microbe-Plant Interactions, Faculty of Biology and Chemistry, Center for Biomolecular Interactions Bremen, University of Bremen, Bremen, Germany
| | - Praveen K. Sappa
- Interfaculty Institute of Genetics and Functional Genomics, University Medicine Greifswald, Greifswald, Germany
| | - Uwe Völker
- Interfaculty Institute of Genetics and Functional Genomics, University Medicine Greifswald, Greifswald, Germany
| | - Theresa Dinse
- Department of Microbe-Plant Interactions, Faculty of Biology and Chemistry, Center for Biomolecular Interactions Bremen, University of Bremen, Bremen, Germany
| | - Julia Herglotz
- Department of Microbe-Plant Interactions, Faculty of Biology and Chemistry, Center for Biomolecular Interactions Bremen, University of Bremen, Bremen, Germany
| | - Barbara Reinhold-Hurek
- Department of Microbe-Plant Interactions, Faculty of Biology and Chemistry, Center for Biomolecular Interactions Bremen, University of Bremen, Bremen, Germany
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66
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Vacheron J, Péchy-Tarr M, Brochet S, Heiman CM, Stojiljkovic M, Maurhofer M, Keel C. T6SS contributes to gut microbiome invasion and killing of an herbivorous pest insect by plant-beneficial Pseudomonas protegens. ISME JOURNAL 2019; 13:1318-1329. [PMID: 30683920 DOI: 10.1038/s41396-019-0353-8] [Citation(s) in RCA: 57] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Revised: 01/09/2019] [Accepted: 01/09/2019] [Indexed: 12/31/2022]
Abstract
Pseudomonas protegens are multi-talented plant-colonizing bacteria that suppress plant pathogens and stimulate plant defenses. In addition, they are capable of invading and killing agriculturally important plant pest insects that makes them promising candidates for biocontrol applications. Here we assessed the role of type VI secretion system (T6SS) components of type strain CHA0 during interaction with larvae of the cabbage pest Pieris brassicae. We show that the T6SS core apparatus and two VgrG modules, encompassing the respective T6SS spikes (VgrG1a and VgrG1b) and associated effectors (RhsA and Ghh1), contribute significantly to insect pathogenicity of P. protegens in oral infection assays but not when bacteria are injected directly into the hemolymph. Monitoring of the colonization levels of P. protegens in the gut, hemolymph, and excrements of the insect larvae revealed that the invader relies on T6SS and VgrG1a module function to promote hemocoel invasion. A 16S metagenomic analysis demonstrated that T6SS-supported invasion by P. protegens induces significant changes in the insect gut microbiome affecting notably Enterobacteriaceae, a dominant group of the commensal gut bacteria. Our study supports the concept that pathogens deploy T6SS-based strategies to disrupt the commensal microbiota in order to promote host colonization and pathogenesis.
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Affiliation(s)
- Jordan Vacheron
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
| | - Maria Péchy-Tarr
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
| | - Silvia Brochet
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
| | - Clara Margot Heiman
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
| | - Marina Stojiljkovic
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
| | - Monika Maurhofer
- Plant Pathology, Institute of Integrative Biology, Swiss Federal Institute of Technology (ETH) Zurich, Zurich, Switzerland.
| | - Christoph Keel
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland.
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67
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Nakamoto N, Sasaki N, Aoki R, Miyamoto K, Suda W, Teratani T, Suzuki T, Koda Y, Chu PS, Taniki N, Yamaguchi A, Kanamori M, Kamada N, Hattori M, Ashida H, Sakamoto M, Atarashi K, Narushima S, Yoshimura A, Honda K, Sato T, Kanai T. Gut pathobionts underlie intestinal barrier dysfunction and liver T helper 17 cell immune response in primary sclerosing cholangitis. Nat Microbiol 2019; 4:492-503. [PMID: 30643240 DOI: 10.1038/s41564-018-0333-1] [Citation(s) in RCA: 258] [Impact Index Per Article: 51.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Accepted: 11/29/2018] [Indexed: 02/07/2023]
Abstract
Primary sclerosing cholangitis (PSC) is a chronic inflammatory liver disease and its frequent complication with ulcerative colitis highlights the pathogenic role of epithelial barrier dysfunction. Intestinal barrier dysfunction has been implicated in the pathogenesis of PSC, yet its underlying mechanism remains unknown. Here, we identify Klebsiella pneumonia in the microbiota of patients with PSC and demonstrate that K. pneumoniae disrupts the epithelial barrier to initiate bacterial translocation and liver inflammatory responses. Gnotobiotic mice inoculated with PSC-derived microbiota exhibited T helper 17 (TH17) cell responses in the liver and increased susceptibility to hepatobiliary injuries. Bacterial culture of mesenteric lymph nodes in these mice isolated K. pneumoniae, Proteus mirabilis and Enterococcus gallinarum, which were prevalently detected in patients with PSC. A bacterial-organoid co-culture system visualized the epithelial-damaging effect of PSC-derived K. pneumoniae that was associated with bacterial translocation and susceptibility to TH17-mediated hepatobiliary injuries. We also show that antibiotic treatment ameliorated the TH17 immune response induced by PSC-derived microbiota. These results highlight the role of pathobionts in intestinal barrier dysfunction and liver inflammation, providing insights into therapeutic strategies for PSC.
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Affiliation(s)
- Nobuhiro Nakamoto
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, Keio University School of Medicine, Shinanomachi, Tokyo, Japan
| | - Nobuo Sasaki
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, Keio University School of Medicine, Shinanomachi, Tokyo, Japan.,AMED-CREST, Japan Agency for Medical Research and Development, Tokyo, Japan
| | - Ryo Aoki
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, Keio University School of Medicine, Shinanomachi, Tokyo, Japan.,Institute of Health Science, Ezaki Glico Co., Ltd, Osaka, Japan
| | - Kentaro Miyamoto
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, Keio University School of Medicine, Shinanomachi, Tokyo, Japan.,Miyarisan Pharmaceutical Co., Ltd, Tokyo, Japan
| | - Wataru Suda
- Department of Microbiology and Immunology, Keio University School of Medicine, Shinanomachi, Tokyo, Japan.,Laboratory of Metagenomics, Department of Computational Biology and Medical Sciences, The University of Tokyo, Chiba, Japan
| | - Toshiaki Teratani
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, Keio University School of Medicine, Shinanomachi, Tokyo, Japan
| | - Takahiro Suzuki
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, Keio University School of Medicine, Shinanomachi, Tokyo, Japan.,Miyarisan Pharmaceutical Co., Ltd, Tokyo, Japan
| | - Yuzo Koda
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, Keio University School of Medicine, Shinanomachi, Tokyo, Japan.,Research Unit/Immunology & Inflammation, Sohyaku Innovative Research Division, Mitsubishi Tanabe Pharma Corporation, Kanagawa, Japan
| | - Po-Sung Chu
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, Keio University School of Medicine, Shinanomachi, Tokyo, Japan
| | - Nobuhito Taniki
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, Keio University School of Medicine, Shinanomachi, Tokyo, Japan
| | - Akihiro Yamaguchi
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, Keio University School of Medicine, Shinanomachi, Tokyo, Japan
| | - Mitsuhiro Kanamori
- Department of Microbiology and Immunology, Keio University School of Medicine, Shinanomachi, Tokyo, Japan
| | - Nobuhiko Kamada
- Division of Gastroenterology, Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Masahira Hattori
- Laboratory of Metagenomics, Department of Computational Biology and Medical Sciences, The University of Tokyo, Chiba, Japan.,Cooperative Major in Advanced Health Science, Graduate School of Advanced Science and Engineering, Faculty of Science and Engineering, Waseda University, Tokyo, Japan
| | - Hiroshi Ashida
- Department of Bacterial Infection and Host Response, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
| | - Michiie Sakamoto
- Department of Pathology, Keio University School of Medicine, Shinanomachi, Tokyo, Japan
| | - Koji Atarashi
- Department of Microbiology and Immunology, Keio University School of Medicine, Shinanomachi, Tokyo, Japan.,RIKEN Center for Integrative Medical Sciences, Laboratory for Gut Homeostasis, Kanagawa, Japan
| | - Seiko Narushima
- Department of Microbiology and Immunology, Keio University School of Medicine, Shinanomachi, Tokyo, Japan.,RIKEN Center for Integrative Medical Sciences, Laboratory for Gut Homeostasis, Kanagawa, Japan
| | - Akihiko Yoshimura
- Department of Microbiology and Immunology, Keio University School of Medicine, Shinanomachi, Tokyo, Japan
| | - Kenya Honda
- Department of Microbiology and Immunology, Keio University School of Medicine, Shinanomachi, Tokyo, Japan.,RIKEN Center for Integrative Medical Sciences, Laboratory for Gut Homeostasis, Kanagawa, Japan
| | - Toshiro Sato
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, Keio University School of Medicine, Shinanomachi, Tokyo, Japan.
| | - Takanori Kanai
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, Keio University School of Medicine, Shinanomachi, Tokyo, Japan. .,AMED-CREST, Japan Agency for Medical Research and Development, Tokyo, Japan.
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68
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Transcriptome and Comparative Genomics Analyses Reveal New Functional Insights on Key Determinants of Pathogenesis and Interbacterial Competition in Pectobacterium and Dickeya spp. Appl Environ Microbiol 2019; 85:AEM.02050-18. [PMID: 30413477 DOI: 10.1128/aem.02050-18] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Accepted: 10/29/2018] [Indexed: 02/07/2023] Open
Abstract
Soft-rot Enterobacteriaceae (SRE), typified by Pectobacterium and Dickeya genera, are phytopathogenic bacteria inflicting soft-rot disease in crops worldwide. By combining genomic information from 100 SRE with whole-transcriptome data sets, we identified novel genomic and transcriptional associations among key pathogenicity themes in this group. Comparative genomics revealed solid linkage between the type I secretion system (T1SS) and the carotovoricin bacteriophage (Ctv) conserved in 96.7% of Pectobacterium genomes. Moreover, their coactivation during infection indicates a novel functional association involving T1SS and Ctv. Another bacteriophage-borne genomic region, mostly confined to less than 10% of Pectobacterium strains, was found, presumably comprising a novel lineage-specific prophage in the genus. We also detected the transcriptional coregulation of a previously predicted toxin/immunity pair (WHH and SMI1_KNR4 families), along with the type VI secretion system (T6SS), which includes hcp and/or vgrG genes, suggesting a role in disease development as T6SS-dependent effectors. Further, we showed that another predicted T6SS-dependent endonuclease (AHH family) exhibited toxicity in ectopic expression assays, indicating antibacterial activity. Additionally, we report the striking conservation of the group 4 capsule (GFC) cluster in 100 SRE strains which consistently features adjacently conserved serotype-specific gene arrays comprising a previously unknown organization in GFC clusters. Also, extensive sequence variations found in gfcA orthologs suggest a serotype-specific role in the GfcABCD machinery.IMPORTANCE Despite the considerable loss inflicted on important crops yearly by Pectobacterium and Dickeya diseases, investigations on key virulence and interbacterial competition assets relying on extensive comparative genomics are still surprisingly lacking for these genera. Such approaches become more powerful over time, underpinned by the growing amount of genomic information in public databases. In particular, our findings point to new functional associations among well-known genomic themes enabling alternative means of neutralizing SRE diseases through disruption of pivotal virulence programs. By elucidating novel transcriptional and genomic associations, this study adds valuable information on virulence candidates that could be decisive in molecular applications in the near future. The utilization of 100 genomes of Pectobacterium and Dickeya strains in this study is unprecedented for comparative analyses in these taxa, and it provides novel insights on the biology of economically important plant pathogens.
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69
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Timmis K, Timmis JK, Brüssow H, Fernández LÁ. Synthetic consortia of nanobody-coupled and formatted bacteria for prophylaxis and therapy interventions targeting microbiome dysbiosis-associated diseases and co-morbidities. Microb Biotechnol 2019; 12:58-65. [PMID: 30575298 PMCID: PMC6302794 DOI: 10.1111/1751-7915.13355] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Designed nanobody-linked synthetic consortia for microbiota dysbiosis therapies. A. Nanobodies (Nb) are selected for specific antigens on target bacteria destined for a synthetic therapy consortium that may consist of two (B) or multiple (C) members. For the treatment of dysbiosis co-morbidities requiring two functionally distinct consortia, these may be linked through a common member to generate a single bi-functional microbiota therapy (D).
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Affiliation(s)
- Kenneth Timmis
- Institute of MicrobiologyTechnical University BraunschweigBraunschweigGermany
| | | | - Harald Brüssow
- Division of Animal and Human Health EngineeringDepartment of BiosystemsKatholieke Universiteit LeuvenLeuvenBelgium
| | - Luis Ángel Fernández
- Department of Microbial BiotechnologyCentro Nacional de BiotecnologíaConsejo Superior de Investigaciones CientíficasMadridSpain
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70
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Ting SY, Bosch DE, Mangiameli SM, Radey MC, Huang S, Park YJ, Kelly KA, Filip SK, Goo YA, Eng JK, Allaire M, Veesler D, Wiggins PA, Peterson SB, Mougous JD. Bifunctional Immunity Proteins Protect Bacteria against FtsZ-Targeting ADP-Ribosylating Toxins. Cell 2018; 175:1380-1392.e14. [PMID: 30343895 PMCID: PMC6239978 DOI: 10.1016/j.cell.2018.09.037] [Citation(s) in RCA: 77] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Revised: 08/13/2018] [Accepted: 09/18/2018] [Indexed: 12/31/2022]
Abstract
ADP-ribosylation of proteins can profoundly impact their function and serves as an effective mechanism by which bacterial toxins impair eukaryotic cell processes. Here, we report the discovery that bacteria also employ ADP-ribosylating toxins against each other during interspecies competition. We demonstrate that one such toxin from Serratia proteamaculans interrupts the division of competing cells by modifying the essential bacterial tubulin-like protein, FtsZ, adjacent to its protomer interface, blocking its capacity to polymerize. The structure of the toxin in complex with its immunity determinant revealed two distinct modes of inhibition: active site occlusion and enzymatic removal of ADP-ribose modifications. We show that each is sufficient to support toxin immunity; however, the latter additionally provides unprecedented broad protection against non-cognate ADP-ribosylating effectors. Our findings reveal how an interbacterial arms race has produced a unique solution for safeguarding the integrity of bacterial cell division machinery against inactivating post-translational modifications.
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Affiliation(s)
- See-Yeun Ting
- Department of Microbiology, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Dustin E Bosch
- Department of Pathology, University of Washington School of Medicine, Seattle, WA 98195, USA
| | | | - Matthew C Radey
- Department of Microbiology, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Shuo Huang
- Department of Microbiology, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Young-Jun Park
- Department of Biochemistry, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Katherine A Kelly
- Department of Microbiology, University of Washington School of Medicine, Seattle, WA 98195, USA
| | | | - Young Ah Goo
- Proteomics Center of Excellence, Northwestern University, Chicago, IL 60611, USA
| | - Jimmy K Eng
- Proteomics Resource, University of Washington, Seattle, WA 98195, USA
| | - Marc Allaire
- Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - David Veesler
- Department of Biochemistry, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Paul A Wiggins
- Department of Microbiology, University of Washington School of Medicine, Seattle, WA 98195, USA; Department of Physics, University of Washington, Seattle, WA 98195, USA; Department of Bioengineering, University of Washington, Seattle, WA 98195, USA
| | - S Brook Peterson
- Department of Microbiology, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Joseph D Mougous
- Department of Microbiology, University of Washington School of Medicine, Seattle, WA 98195, USA; Department of Biochemistry, University of Washington School of Medicine, Seattle, WA 98195, USA; Howard Hughes Medical Institute, University of Washington, Seattle, WA 98195, USA.
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71
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Biogenesis and structure of a type VI secretion baseplate. Nat Microbiol 2018; 3:1404-1416. [DOI: 10.1038/s41564-018-0260-1] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2018] [Accepted: 08/31/2018] [Indexed: 12/20/2022]
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72
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In vivo TssA proximity labelling during type VI secretion biogenesis reveals TagA as a protein that stops and holds the sheath. Nat Microbiol 2018; 3:1304-1313. [DOI: 10.1038/s41564-018-0234-3] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Accepted: 07/31/2018] [Indexed: 12/14/2022]
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73
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Bacterial symbionts use a type VI secretion system to eliminate competitors in their natural host. Proc Natl Acad Sci U S A 2018; 115:E8528-E8537. [PMID: 30127013 PMCID: PMC6130350 DOI: 10.1073/pnas.1808302115] [Citation(s) in RCA: 103] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Competition among cooccurring bacteria can change the structure and function of a microbial community. However, little is known about the molecular mechanisms that impact such interactions in vivo. We used the association between bioluminescent bacteria and their squid host to study how environmentally transmitted bacteria compete for a limited number of host colonization sites. Our work suggests that Vibrio fischeri use a type VI secretion system, acting as a contact-dependent interbacterial “weapon,” to eliminate competing strains from cooccupying sites in the host. This work illuminates a mechanism by which strain-specific differences drive closely related bacteria to engage in lethal battles as they establish a beneficial symbiosis, revealing how genetic variation among potential colonizers directly impacts the spatial structure of the host-associated population. Intraspecific competition describes the negative interaction that occurs when different populations of the same species attempt to fill the same niche. Such competition is predicted to occur among host-associated bacteria but has been challenging to study in natural biological systems. Although many bioluminescent Vibrio fischeri strains exist in seawater, only a few strains are found in the light-organ crypts of an individual wild-caught Euprymna scolopes squid, suggesting a possible role for intraspecific competition during early colonization. Using a culture-based assay to investigate the interactions of different V. fischeri strains, we found “lethal” and “nonlethal” isolates that could kill or not kill the well-studied light-organ isolate ES114, respectively. The killing phenotype of these lethal strains required a type VI secretion system (T6SS) encoded in a 50-kb genomic island. Multiple lethal and nonlethal strains could be cultured from the light organs of individual wild-caught adult squid. Although lethal strains eliminate nonlethal strains in vitro, two lethal strains could coexist in interspersed microcolonies that formed in a T6SS-dependent manner. This coexistence was destabilized upon physical mixing, resulting in one lethal strain consistently eliminating the other. When juvenile squid were coinoculated with lethal and nonlethal strains, they occupied different crypts, yet they were observed to coexist within crypts when T6SS function was disrupted. These findings, using a combination of natural isolates and experimental approaches in vitro and in the animal host, reveal the importance of T6SS in spatially separating strains during the establishment of host colonization in a natural symbiosis.
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Lin HH, Huang HM, Yu M, Lai EM, Chien HL, Liu CT. Functional Exploration of the Bacterial Type VI Secretion System in Mutualism: Azorhizobium caulinodans ORS571-Sesbania rostrata as a Research Model. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2018. [PMID: 29516754 DOI: 10.1094/mpmi-01-18-0026-r] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
The bacterial type VI secretion system (T6SS) has been considered the armed force of bacteria because it can deliver toxin effectors to prokaryotic or eukaryotic cells for survival and fitness. Although many legume symbiotic rhizobacteria encode T6SS in their genome, the biological function of T6SS in these bacteria is still unclear. To elucidate this issue, we used Azorhizobium caulinodans ORS571 and its symbiotic host Sesbania rostrata as our research model. By using T6SS gene deletion mutants, we found that T6SS provides A. caulinodans with better symbiotic competitiveness when coinfected with a T6SS-lacking strain, as demonstrated by two independent T6SS-deficient mutants. Meanwhile, the symbiotic effectiveness was not affected by T6SS because the nodule phenotype, nodule size, and nodule nitrogen-fixation ability did not differ between the T6SS mutants and the wild type when infected alone. Our data also suggest that under several lab culture conditions tested, A. caulinodans showed no T6SS-dependent interbacterial competition activity. Therefore, instead of being an antihost or antibacterial weapon of the bacterium, the T6SS in A. caulinodans ORS571 seems to participate specifically in symbiosis by increasing its symbiotic competitiveness.
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Affiliation(s)
- Hsiao-Han Lin
- 1 Institute of Biotechnology, National Taiwan University, No. 81, Chang-Xing St., Taipei 10617, Taiwan
- 2 Institute of Plant and Microbial Biology, Academia Sinica, No. 128 Section 2, Academia Rd., Nankang, Taipei 11529, Taiwan; and
| | - Hsin-Mei Huang
- 1 Institute of Biotechnology, National Taiwan University, No. 81, Chang-Xing St., Taipei 10617, Taiwan
| | - Manda Yu
- 2 Institute of Plant and Microbial Biology, Academia Sinica, No. 128 Section 2, Academia Rd., Nankang, Taipei 11529, Taiwan; and
| | - Erh-Min Lai
- 2 Institute of Plant and Microbial Biology, Academia Sinica, No. 128 Section 2, Academia Rd., Nankang, Taipei 11529, Taiwan; and
| | - Hsiao-Lin Chien
- 1 Institute of Biotechnology, National Taiwan University, No. 81, Chang-Xing St., Taipei 10617, Taiwan
| | - Chi-Te Liu
- 1 Institute of Biotechnology, National Taiwan University, No. 81, Chang-Xing St., Taipei 10617, Taiwan
- 3 Agricultural Biotechnology Research Center, Academia Sinica
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75
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Trunk K, Peltier J, Liu YC, Dill BD, Walker L, Gow NAR, Stark MJR, Quinn J, Strahl H, Trost M, Coulthurst SJ. The type VI secretion system deploys antifungal effectors against microbial competitors. Nat Microbiol 2018; 3:920-931. [PMID: 30038307 PMCID: PMC6071859 DOI: 10.1038/s41564-018-0191-x] [Citation(s) in RCA: 136] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2017] [Accepted: 06/07/2018] [Indexed: 12/28/2022]
Abstract
Interactions between bacterial and fungal cells shape many polymicrobial communities. Bacteria elaborate diverse strategies to interact and compete with other organisms, including the deployment of protein secretion systems. The type VI secretion system (T6SS) delivers toxic effector proteins into host eukaryotic cells and competitor bacterial cells, but, surprisingly, T6SS-delivered effectors targeting fungal cells have not been reported. Here we show that the 'antibacterial' T6SS of Serratia marcescens can act against fungal cells, including pathogenic Candida species, and identify the previously undescribed effector proteins responsible. These antifungal effectors, Tfe1 and Tfe2, have distinct impacts on the target cell, but both can ultimately cause fungal cell death. 'In competition' proteomics analysis revealed that T6SS-mediated delivery of Tfe2 disrupts nutrient uptake and amino acid metabolism in fungal cells, and leads to the induction of autophagy. Intoxication by Tfe1, in contrast, causes a loss of plasma membrane potential. Our findings extend the repertoire of the T6SS and suggest that antifungal T6SSs represent widespread and important determinants of the outcome of bacterial-fungal interactions.
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Affiliation(s)
- Katharina Trunk
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee, UK
| | - Julien Peltier
- MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dundee, UK
- Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle-upon-Tyne, UK
| | - Yi-Chia Liu
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee, UK
| | - Brian D Dill
- MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dundee, UK
| | - Louise Walker
- Aberdeen Fungal Group, Institute of Medical Sciences, MRC Centre for Medical Mycology at the University of Aberdeen, Aberdeen, UK
| | - Neil A R Gow
- Aberdeen Fungal Group, Institute of Medical Sciences, MRC Centre for Medical Mycology at the University of Aberdeen, Aberdeen, UK
| | - Michael J R Stark
- Centre for Gene Regulation and Expression, School of Life Sciences, University of Dundee, Dundee, UK
| | - Janet Quinn
- Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle-upon-Tyne, UK
| | - Henrik Strahl
- Centre for Bacterial Cell Biology, Newcastle University, Newcastle-upon-Tyne, UK
| | - Matthias Trost
- MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dundee, UK.
- Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle-upon-Tyne, UK.
| | - Sarah J Coulthurst
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee, UK.
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76
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Alam A, Golovliov I, Javed E, Sjöstedt A. ClpB mutants of Francisella tularensis subspecies holarctica and tularensis are defective for type VI secretion and intracellular replication. Sci Rep 2018; 8:11324. [PMID: 30054549 PMCID: PMC6063899 DOI: 10.1038/s41598-018-29745-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Accepted: 07/17/2018] [Indexed: 12/13/2022] Open
Abstract
Francisella tularensis, a highly infectious, intracellular bacterium possesses an atypical type VI secretion system (T6SS), which is essential for the virulence of the bacterium. Recent data suggest that the HSP100 family member, ClpB, is involved in T6SS disassembly in the subspecies Francisella novicida. Here, we investigated the role of ClpB for the function of the T6SS and for phenotypic characteristics of the human pathogenic subspecies holarctica and tularensis. The ∆clpB mutants of the human live vaccine strain, LVS, belonging to subspecies holarctica, and the highly virulent SCHU S4 strain, belonging to subspecies tularensis, both showed extreme susceptibility to heat shock and low pH, severely impaired type VI secretion (T6S), and significant, but impaired intracellular replication compared to the wild-type strains. Moreover, they showed essentially intact phagosomal escape. Infection of mice demonstrated that both ΔclpB mutants were highly attenuated, but the SCHU S4 mutant showed more effective replication than the LVS strain. Collectively, our data demonstrate that ClpB performs multiple functions in the F. tularensis subspecies holarctica and tularensis and its function is important for T6S, intracellular replication, and virulence.
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Affiliation(s)
- Athar Alam
- Department of Clinical Microbiology, Umeå University, SE-901 85, Umeå, Sweden
| | - Igor Golovliov
- Department of Clinical Microbiology, Umeå University, SE-901 85, Umeå, Sweden
| | - Eram Javed
- Department of Clinical Microbiology, Umeå University, SE-901 85, Umeå, Sweden
| | - Anders Sjöstedt
- Department of Clinical Microbiology, Umeå University, SE-901 85, Umeå, Sweden.
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77
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Identification of Novel Acinetobacter baumannii Type VI Secretion System Antibacterial Effector and Immunity Pairs. Infect Immun 2018; 86:IAI.00297-18. [PMID: 29735524 DOI: 10.1128/iai.00297-18] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Accepted: 05/04/2018] [Indexed: 12/21/2022] Open
Abstract
The type VI secretion system (T6SS) is a macromolecular machine that delivers protein effectors into host cells and/or competing bacteria. The effectors may be delivered as noncovalently bound cargo of T6SS needle proteins (VgrG/Hcp/PAAR) or as C-terminal extensions of these proteins. Many Acinetobacter baumannii strains produce a T6SS, but little is known about the specific effectors or how they are delivered. In this study, we show that A. baumannii AB307-0294 encodes three vgrG loci, each containing a vgrG gene, a T6SS toxic effector gene, and an antitoxin/immunity gene. Each of the T6SS toxic effectors could kill Escherichia coli when produced in trans unless the cognate immunity protein was coproduced. To determine the role of each VgrG in effector delivery, we performed interbacterial competitive killing assays using A. baumannii AB307-0294 vgrG mutants, together with Acinetobacter baylyi prey cells expressing pairs of immunity genes that protected against two toxic effectors but not a third. Using this approach, we showed that AB307-0294 produces only three T6SS toxic effectors capable of killing A. baylyi and that each VgrG protein is specific for the carriage of one effector. Finally, we analyzed a number of A. baumannii genomes and identified significant diversity in the range of encoded T6SS VgrG and effector proteins, with correlations between effector types and A. baumannii global clone lineages.
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78
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Renault MG, Zamarreno Beas J, Douzi B, Chabalier M, Zoued A, Brunet YR, Cambillau C, Journet L, Cascales E. The gp27-like Hub of VgrG Serves as Adaptor to Promote Hcp Tube Assembly. J Mol Biol 2018; 430:3143-3156. [PMID: 30031895 DOI: 10.1016/j.jmb.2018.07.018] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2017] [Revised: 07/06/2018] [Accepted: 07/12/2018] [Indexed: 12/25/2022]
Abstract
Contractile injection systems are multiprotein complexes that use a spring-like mechanism to deliver effectors into target cells. In addition to using a conserved mechanism, these complexes share a common core known as the tail. The tail comprises an inner tube tipped by a spike, wrapped by a contractile sheath, and assembled onto a baseplate. Here, using the type VI secretion system (T6SS) as a model of contractile injection systems, we provide molecular details on the interaction between the inner tube and the spike. Reconstitution into the Escherichia coli heterologous host in the absence of other T6SS components and in vitro experiments demonstrated that the Hcp tube component and the VgrG spike interact directly. VgrG deletion studies coupled to functional assays showed that the N-terminal domain of VgrG is sufficient to interact with Hcp, to initiate proper Hcp tube polymerization, and to promote sheath dynamics and Hcp release. The interaction interface between Hcp and VgrG was then mapped using docking simulations, mutagenesis, and cysteine-mediated cross-links. Based on these results, we propose a model in which the VgrG base serves as adaptor to recruit the first Hcp hexamer and initiates inner tube polymerization.
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Affiliation(s)
- Melvin G Renault
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie de la Méditerranée (IMM), Aix-Marseille Univ-Centre National de la Recherche Scientifique (CNRS), UMR7255, 31 chemin Joseph Aiguier, 13402 Marseille Cedex 20, France
| | - Jordi Zamarreno Beas
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie de la Méditerranée (IMM), Aix-Marseille Univ-Centre National de la Recherche Scientifique (CNRS), UMR7255, 31 chemin Joseph Aiguier, 13402 Marseille Cedex 20, France
| | - Badreddine Douzi
- Architecture et Fonction des Macromolécules Biologiques (AFMB), Aix-Marseille Univ-Centre National de la Recherche Scientifique (CNRS), UMR 7257, Campus de Luminy, Case 932, 13288 Marseille Cedex, 09, France
| | - Maïalène Chabalier
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie de la Méditerranée (IMM), Aix-Marseille Univ-Centre National de la Recherche Scientifique (CNRS), UMR7255, 31 chemin Joseph Aiguier, 13402 Marseille Cedex 20, France
| | - Abdelrahim Zoued
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie de la Méditerranée (IMM), Aix-Marseille Univ-Centre National de la Recherche Scientifique (CNRS), UMR7255, 31 chemin Joseph Aiguier, 13402 Marseille Cedex 20, France
| | - Yannick R Brunet
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie de la Méditerranée (IMM), Aix-Marseille Univ-Centre National de la Recherche Scientifique (CNRS), UMR7255, 31 chemin Joseph Aiguier, 13402 Marseille Cedex 20, France
| | - Christian Cambillau
- Architecture et Fonction des Macromolécules Biologiques (AFMB), Aix-Marseille Univ-Centre National de la Recherche Scientifique (CNRS), UMR 7257, Campus de Luminy, Case 932, 13288 Marseille Cedex, 09, France
| | - Laure Journet
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie de la Méditerranée (IMM), Aix-Marseille Univ-Centre National de la Recherche Scientifique (CNRS), UMR7255, 31 chemin Joseph Aiguier, 13402 Marseille Cedex 20, France
| | - Eric Cascales
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie de la Méditerranée (IMM), Aix-Marseille Univ-Centre National de la Recherche Scientifique (CNRS), UMR7255, 31 chemin Joseph Aiguier, 13402 Marseille Cedex 20, France.
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79
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Ostrowski A, Cianfanelli FR, Porter M, Mariano G, Peltier J, Wong JJ, Swedlow JR, Trost M, Coulthurst SJ. Killing with proficiency: Integrated post-translational regulation of an offensive Type VI secretion system. PLoS Pathog 2018; 14:e1007230. [PMID: 30052683 PMCID: PMC6082577 DOI: 10.1371/journal.ppat.1007230] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Revised: 08/08/2018] [Accepted: 07/17/2018] [Indexed: 11/20/2022] Open
Abstract
The Type VI secretion system (T6SS) is widely used by bacterial pathogens as an effective weapon against bacterial competitors and is also deployed against host eukaryotic cells in some cases. It is a contractile nanomachine which delivers toxic effector proteins directly into target cells by dynamic cycles of assembly and firing. Bacterial cells adopt distinct post-translational regulatory strategies for deployment of the T6SS. 'Defensive' T6SSs assemble and fire in response to incoming attacks from aggressive neighbouring cells, and can utilise the Threonine Protein Phosphorylation (TPP) regulatory pathway to achieve this control. However, many T6SSs are 'offensive', firing at all-comers without the need for incoming attack or other cell contact-dependent signal. Post-translational control of the offensive mode has been less well defined but can utilise components of the same TPP pathway. Here, we used the anti-bacterial T6SS of Serratia marcescens to elucidate post-translational regulation of offensive T6SS deployment, using single-cell microscopy and genetic analyses. We show that the integration of the TPP pathway with the negative regulator TagF to control core T6SS machine assembly is conserved between offensive and defensive T6SSs. Signal-dependent PpkA-mediated phosphorylation of Fha is required to overcome inhibition of membrane complex assembly by TagF, whilst PppA-mediated dephosphorylation promotes spatial reorientation and efficient killing. In contrast, the upstream input of the TPP pathway defines regulatory strategy, with a new periplasmic regulator, RtkS, shown to interact with the PpkA kinase in S. marcescens. We propose a model whereby the opposing actions of the TPP pathway and TagF impose a delay on T6SS re-assembly after firing, providing an opportunity for spatial re-orientation of the T6SS in order to maximise the efficiency of competitor cell targeting. Our findings provide a better understanding of how bacterial cells deploy competitive weapons effectively, with implications for the structure and dynamics of varied polymicrobial communities.
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Affiliation(s)
- Adam Ostrowski
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Francesca R. Cianfanelli
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Michael Porter
- Centre for Gene Regulation and Expression, School of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Giuseppina Mariano
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Julien Peltier
- Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle-upon-Tyne, United Kingdom
- MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Jun Jie Wong
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Jason R. Swedlow
- Centre for Gene Regulation and Expression, School of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Matthias Trost
- Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle-upon-Tyne, United Kingdom
- MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Sarah J. Coulthurst
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee, United Kingdom
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80
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Alcoforado Diniz J, Hollmann B, Coulthurst SJ. Quantitative Determination of Anti-bacterial Activity During Bacterial Co-culture. Methods Mol Biol 2018; 1615:517-524. [PMID: 28667634 DOI: 10.1007/978-1-4939-7033-9_36] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
Abstract
Anti-bacterial activity assays are an important tool in the assessment of the ability of one bacterium to kill or inhibit the growth of another, for example during the study of the Type VI secretion system (T6SS) and the anti-bacterial toxins it secretes. The method we describe here can detect the ability of a bacterial strain to kill or inhibit other bacterial cells in a contact-dependent manner when co-cultured on an agar surface. It is particularly useful since it enumerates the recovery of viable target cells and thus enables quantification of the anti-bacterial activity. We provide a detailed description of how to measure the T6SS-dependent anti-bacterial activity of a bacterium such as Serratia marcescens against a competitor prokaryotic organism, Escherichia coli, and also describe possible variations in the method to allow adaptation to other attacker and target organisms.
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Affiliation(s)
- Juliana Alcoforado Diniz
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dow Street, Dundee, DD1 5EH, UK
| | - Birte Hollmann
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dow Street, Dundee, DD1 5EH, UK
| | - Sarah J Coulthurst
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dow Street, Dundee, DD1 5EH, UK.
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81
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Elhosseiny NM, Attia AS. Acinetobacter: an emerging pathogen with a versatile secretome. Emerg Microbes Infect 2018; 7:33. [PMID: 29559620 PMCID: PMC5861075 DOI: 10.1038/s41426-018-0030-4] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Revised: 12/08/2017] [Accepted: 01/09/2018] [Indexed: 02/06/2023]
Abstract
Acinetobacter baumannii is a notorious pathogen that has emerged as a healthcare nightmare in recent years because it causes serious infections that are associated with high morbidity and mortality rates. Due to its exceptional ability to acquire resistance to almost all available antibiotics, A. baumannii is currently ranked as the first pathogen on the World Health Organization’s priority list for the development of new antibiotics. The versatile range of effectors secreted by A. baumannii represents a large proportion of the virulence arsenal identified in this bacterium to date. Thus, these factors, together with the secretory machinery responsible for their extrusion into the extracellular milieu, are key targets for novel therapeutics that are greatly needed to combat this deadly pathogen. In this review, we provide a comprehensive, up-to-date overview of the organization and regulatory aspects of the Acinetobacter secretion systems, with a special emphasis on their versatile substrates that could be targeted to fight the deadly infections caused by this elusive pathogen.
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Affiliation(s)
- Noha M Elhosseiny
- Department of Microbiology and Immunology, Faculty of Pharmacy, Cairo University, Cairo, 11562, Egypt
| | - Ahmed S Attia
- Department of Microbiology and Immunology, Faculty of Pharmacy, Cairo University, Cairo, 11562, Egypt.
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82
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LaCourse KD, Peterson SB, Kulasekara HD, Radey MC, Kim J, Mougous JD. Conditional toxicity and synergy drive diversity among antibacterial effectors. Nat Microbiol 2018; 3:440-446. [PMID: 29459733 PMCID: PMC5876133 DOI: 10.1038/s41564-018-0113-y] [Citation(s) in RCA: 77] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2017] [Accepted: 01/16/2018] [Indexed: 12/19/2022]
Abstract
Bacteria in polymicrobial habitats contend with a persistent barrage of competitors, often under rapidly changing environmental conditions1. The direct antagonism of competitor cells is thus an important bacterial survival strategy2. Towards this end, many bacterial species employ an arsenal of antimicrobial effectors with multiple activities; however, the benefits conferred by the simultaneous deployment of diverse toxins are unknown. Here we show that the multiple effectors delivered to competitor bacteria by the type VI secretion system (T6SS) of Pseudomonas aeruginosa display conditional efficacy and act synergistically. One of these effectors, Tse4, is most active in high salinity environments and synergizes with effectors that degrade the cell wall or inactivate intracellular electron carriers. We find Tse4 synergizes with these disparate mechanisms by forming pores that disrupt the ΔΨ component of the proton motive force. Our results provide evidence that the concomitant delivery of a cocktail of effectors serves as a bet-hedging strategy to promote bacterial competitiveness in the face of unpredictable and variable environmental conditions.
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Affiliation(s)
| | - S Brook Peterson
- Department of Microbiology, University of Washington, Seattle, WA, USA
| | | | - Matthew C Radey
- Department of Microbiology, University of Washington, Seattle, WA, USA
| | - Jungyun Kim
- Department of Microbiology, University of Washington, Seattle, WA, USA
| | - Joseph D Mougous
- Department of Microbiology, University of Washington, Seattle, WA, USA. .,Howard Hughes Medical Institute, University of Washington, Seattle, WA, USA.
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83
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Chassaing B, Cascales E. Antibacterial Weapons: Targeted Destruction in the Microbiota. Trends Microbiol 2018; 26:329-338. [PMID: 29452951 DOI: 10.1016/j.tim.2018.01.006] [Citation(s) in RCA: 87] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2017] [Revised: 01/18/2018] [Accepted: 01/23/2018] [Indexed: 01/18/2023]
Abstract
The intestinal microbiota plays an important role in health, particularly in promoting intestinal metabolic capacity and in maturing the immune system. The intestinal microbiota also mediates colonization resistance against pathogenic bacteria, hence protecting the host from infections. In addition, some bacterial pathogens deliver toxins that target phylogenetically related or distinct bacterial species in order to outcompete and establish within the microbiota. The most widely distributed weapons include bacteriocins, as well as contact-dependent growth inhibition and type VI secretion systems. In this review, we discuss important advances about the impact of such antibacterial systems on shaping the intestinal microbiota.
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Affiliation(s)
- Benoit Chassaing
- Neuroscience Institute, Georgia State University, Atlanta, GA, USA; Institute for Biomedical Sciences, Georgia State University, Atlanta, GA, USA.
| | - Eric Cascales
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie de la Méditerranée (IMM), Aix-Marseille Univ - Centre National de la Recherche Scientifique (CNRS) UMR7255, Marseille, France.
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84
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Structure and activity of ChiX: a peptidoglycan hydrolase required for chitinase secretion by Serratia marcescens. Biochem J 2018; 475:415-428. [PMID: 29229757 PMCID: PMC5778951 DOI: 10.1042/bcj20170633] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Revised: 12/05/2017] [Accepted: 12/07/2017] [Indexed: 11/17/2022]
Abstract
The Gram-negative bacterium Serratia marcescens secretes many proteins that are involved in extracellular chitin degradation. This so-called chitinolytic machinery includes three types of chitinase enzymes and a lytic polysaccharide monooxygenase. An operon has been identified in S. marcescens, chiWXYZ, that is thought to be involved in the secretion of the chitinolytic machinery. Genetic evidence points to the ChiX protein being a key player in the secretion mechanism, since deletion of the chiX gene in S. marcescens led to a mutant strain blocked for secretion of all members of the chitinolytic machinery. In this work, a detailed structural and biochemical characterisation of ChiX is presented. The high-resolution crystal structure of ChiX reveals the protein to be a member of the LAS family of peptidases. ChiX is shown to be a zinc-containing metalloenzyme, and in vitro assays demonstrate that ChiX is an l-Ala d-Glu endopeptidase that cleaves the cross-links in bacterial peptidoglycan. This catalytic activity is shown to be intimately linked with the secretion of the chitinolytic machinery, since substitution of the ChiX Asp-120 residue results in a variant protein that is both unable to digest peptidoglycan and cannot rescue the phenoytype of a chiX mutant strain.
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85
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Nazarov S, Schneider JP, Brackmann M, Goldie KN, Stahlberg H, Basler M. Cryo-EM reconstruction of Type VI secretion system baseplate and sheath distal end. EMBO J 2017; 37:embj.201797103. [PMID: 29255010 PMCID: PMC5813253 DOI: 10.15252/embj.201797103] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2017] [Revised: 11/09/2017] [Accepted: 11/16/2017] [Indexed: 01/02/2023] Open
Abstract
The bacterial Type VI secretion system (T6SS) assembles from three major parts: a membrane complex that spans inner and outer membranes, a baseplate, and a sheath-tube polymer. The baseplate assembles around a tip complex with associated effectors and connects to the membrane complex by TssK. The baseplate assembly initiates sheath-tube polymerization, which in some organisms requires TssA. Here, we analyzed both ends of isolated non-contractile Vibrio cholerae sheaths by cryo-electron microscopy. Our analysis suggests that the baseplate, solved to an average 8.0 Å resolution, is composed of six subunits of TssE/F2/G and the baseplate periphery is decorated by six TssK trimers. The VgrG/PAAR tip complex in the center of the baseplate is surrounded by a cavity, which may accommodate up to ~450 kDa of effector proteins. The distal end of the sheath, resolved to an average 7.5 Å resolution, shows sixfold symmetry; however, its protein composition is unclear. Our structures provide an important step toward an atomic model of the complete T6SS assembly.
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Affiliation(s)
- Sergey Nazarov
- Focal Area Infection Biology, Biozentrum, University of Basel, Basel, Switzerland
| | - Johannes P Schneider
- Focal Area Infection Biology, Biozentrum, University of Basel, Basel, Switzerland
| | - Maximilian Brackmann
- Focal Area Infection Biology, Biozentrum, University of Basel, Basel, Switzerland
| | - Kenneth N Goldie
- Center for Cellular Imaging and NanoAnalytics, Biozentrum, University of Basel, Basel, Switzerland
| | - Henning Stahlberg
- Center for Cellular Imaging and NanoAnalytics, Biozentrum, University of Basel, Basel, Switzerland.,Focal Area Structural Biology, Biozentrum, University of Basel, Basel, Switzerland
| | - Marek Basler
- Focal Area Infection Biology, Biozentrum, University of Basel, Basel, Switzerland
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86
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de Campos SB, Lardi M, Gandolfi A, Eberl L, Pessi G. Mutations in Two Paraburkholderia phymatum Type VI Secretion Systems Cause Reduced Fitness in Interbacterial Competition. Front Microbiol 2017; 8:2473. [PMID: 29312183 PMCID: PMC5732942 DOI: 10.3389/fmicb.2017.02473] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Accepted: 11/28/2017] [Indexed: 12/14/2022] Open
Abstract
Paraburkholderia phymatum is a highly effective microsymbiont of Mimosa spp. and has also been shown to nodulate papilionoid legumes. P. phymatum was found to be highly competitive both in a natural environment as well as under controlled test conditions and is more competitive for nodulation over other α- and β-rhizobial strains in a variety of different plant hosts. In order to elucidate the factors that make this bacterium highly competitive for legume infection, we here characterized the type VI secretion system (T6SS) clusters of P. phymatum. T6SSs have been shown to function as a contact-dependent injection system for both bacterial and eukaryotic cells. We identified two T6SS clusters in the genome, created respective mutant strains and showed that they are defective in biofilm formation and in interbacterial competition in vitro. While the T6SS mutants were as efficient as the wild-type in nodulating the non-cognate host Vigna unguiculata, the mutants were less competitive in in planta competition assays, suggesting that the T6SS is one of the factors responsible for the success of P. phymatum in infecting legumes by directly inhibiting competitors.
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Affiliation(s)
| | - Martina Lardi
- Institute of Plant and Microbial Biology, University of Zurich, Zurich, Switzerland
| | - Alessia Gandolfi
- Institute of Plant and Microbial Biology, University of Zurich, Zurich, Switzerland
| | - Leo Eberl
- Institute of Plant and Microbial Biology, University of Zurich, Zurich, Switzerland
| | - Gabriella Pessi
- Institute of Plant and Microbial Biology, University of Zurich, Zurich, Switzerland
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87
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Brackmann M, Wang J, Basler M. Type VI secretion system sheath inter-subunit interactions modulate its contraction. EMBO Rep 2017; 19:225-233. [PMID: 29222345 PMCID: PMC5797969 DOI: 10.15252/embr.201744416] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Revised: 11/07/2017] [Accepted: 11/17/2017] [Indexed: 11/09/2022] Open
Abstract
Secretion systems are essential for bacteria to survive and manipulate their environment. The bacterial type VI secretion system (T6SS) generates the force needed for protein translocation by the contraction of a long polymer called sheath. The sheath is a six-start helical assembly of interconnected VipA/VipB subunits. The mechanism of T6SS sheath contraction is unknown. Here, we show that elongating the N-terminal VipA linker or eliminating charge of a specific VipB residue abolishes sheath contraction and delivery of effectors into target cells. Mass spectrometry analysis identified the inner tube protein Hcp, spike protein VgrG, and other components of the T6SS baseplate significantly enriched in samples of the stable non-contractile sheaths. The ability to lock the T6SS in the pre-firing state opens new possibilities for understanding its mode of action.
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Affiliation(s)
- Maximilian Brackmann
- Focal Area Infection Biology, Biozentrum, University of Basel, Basel, Switzerland
| | - Jing Wang
- Focal Area Infection Biology, Biozentrum, University of Basel, Basel, Switzerland
| | - Marek Basler
- Focal Area Infection Biology, Biozentrum, University of Basel, Basel, Switzerland
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88
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Douzi B, Logger L, Spinelli S, Blangy S, Cambillau C, Cascales E. Structure-Function Analysis of the C-Terminal Domain of the Type VI Secretion TssB Tail Sheath Subunit. J Mol Biol 2017; 430:297-309. [PMID: 29223729 DOI: 10.1016/j.jmb.2017.11.015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2017] [Revised: 11/26/2017] [Accepted: 11/30/2017] [Indexed: 11/16/2022]
Abstract
The type VI secretion system (T6SS) is a specialized macromolecular complex dedicated to the delivery of protein effectors into both eukaryotic and bacterial cells. The general mechanism of action of the T6SS is similar to the injection of DNA by contractile bacteriophages. The cytoplasmic portion of the T6SS is evolutionarily, structurally and functionally related to the phage tail complex. It is composed of an inner tube made of stacked Hcp hexameric rings, engulfed within a sheath and built on a baseplate. This sheath undergoes cycles of extension and contraction, and the current model proposes that the sheath contraction propels the inner tube toward the target cell for effector delivery. The sheath comprises two subunits: TssB and TssC that polymerize under an extended conformation. Here, we show that isolated TssB forms trimers, and we report the crystal structure of a C-terminal fragment of TssB. This fragment comprises a long helix followed by a helical hairpin that presents surface-exposed charged residues. Site-directed mutagenesis coupled to functional assay further showed that these charges are required for proper assembly of the sheath. Positioning of these residues in the extended T6SS sheath structure suggests that they may mediate contacts with the baseplate.
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Affiliation(s)
- Badreddine Douzi
- Architecture et Fonction des Macromolécules Biologiques (AFMB), Aix-Marseille Univ-Centre National de la Recherche Scientifique (CNRS), UMR 7257, Campus de Luminy, Case 932, 13288 Marseille Cedex 09, France
| | - Laureen Logger
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie de la Méditerranée (IMM), Aix-Marseille Univ-Centre National de la Recherche Scientifique (CNRS), UMR7255, 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20, France
| | - Silvia Spinelli
- Architecture et Fonction des Macromolécules Biologiques (AFMB), Aix-Marseille Univ-Centre National de la Recherche Scientifique (CNRS), UMR 7257, Campus de Luminy, Case 932, 13288 Marseille Cedex 09, France
| | - Stéphanie Blangy
- Architecture et Fonction des Macromolécules Biologiques (AFMB), Aix-Marseille Univ-Centre National de la Recherche Scientifique (CNRS), UMR 7257, Campus de Luminy, Case 932, 13288 Marseille Cedex 09, France
| | - Christian Cambillau
- Architecture et Fonction des Macromolécules Biologiques (AFMB), Aix-Marseille Univ-Centre National de la Recherche Scientifique (CNRS), UMR 7257, Campus de Luminy, Case 932, 13288 Marseille Cedex 09, France.
| | - Eric Cascales
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie de la Méditerranée (IMM), Aix-Marseille Univ-Centre National de la Recherche Scientifique (CNRS), UMR7255, 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20, France.
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89
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Yu Z, Beck DAC, Chistoserdova L. Natural Selection in Synthetic Communities Highlights the Roles of Methylococcaceae and Methylophilaceae and Suggests Differential Roles for Alternative Methanol Dehydrogenases in Methane Consumption. Front Microbiol 2017; 8:2392. [PMID: 29259591 PMCID: PMC5723320 DOI: 10.3389/fmicb.2017.02392] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Accepted: 11/20/2017] [Indexed: 12/31/2022] Open
Abstract
We describe experiments that follow species dynamics and gene expression patterns in synthetic bacterial communities including species that compete for the single carbon substrate supplied, methane, and species unable to consume methane, which could only succeed through cooperative interactions. We demonstrate that these communities mostly select for two functional guilds, methanotrophs of the family Methylococcaceae and non-methanotrophic methylotrophs of the family Methylophilaceae, these taxonomic guilds outcompeting all other species included in the synthetic mix. The metatranscriptomics analysis uncovered that in both Methylococcaceae and Methylophilaceae, some of the most highly transcribed genes were the ones encoding methanol dehydrogenases (MDH). Remarkably, expression of alternative MDH genes (mxaFI versus xoxF), previously shown to be subjects to the rare Earth element switch, was found to depend on environmental conditions such as nitrogen source and methane and O2 partial pressures, and also to be species-specific. Along with the xoxF genes, genes encoding divergent cytochromes were highly expressed in both Methylophilaceae and Methylococcaceae, suggesting their function in methanol metabolism, likely encoding proteins serving as electron acceptors from XoxF enzymes. The research presented tested a synthetic community model that is much simplified compared to natural communities consuming methane, but more complex than the previously utilized two-species model. The performance of this model identifies prominent species for future synthetic ecology experiments and highlights both advantages of this approach and the challenges that it presents.
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Affiliation(s)
- Zheng Yu
- Department of Chemical Engineering, University of Washington, Seattle, WA, United States
| | - David A C Beck
- Department of Chemical Engineering, University of Washington, Seattle, WA, United States.,eScience Institute, University of Washington, Seattle, WA, United States
| | - Ludmila Chistoserdova
- Department of Chemical Engineering, University of Washington, Seattle, WA, United States
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90
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Kim IH, Aryal SK, Aghai DT, Casanova-Torres ÁM, Hillman K, Kozuch MP, Mans EJ, Mauer TJ, Ogier JC, Ensign JC, Gaudriault S, Goodman WG, Goodrich-Blair H, Dillman AR. The insect pathogenic bacterium Xenorhabdus innexi has attenuated virulence in multiple insect model hosts yet encodes a potent mosquitocidal toxin. BMC Genomics 2017; 18:927. [PMID: 29191166 PMCID: PMC5709968 DOI: 10.1186/s12864-017-4311-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Accepted: 11/16/2017] [Indexed: 11/25/2022] Open
Abstract
BACKGROUND Xenorhabdus innexi is a bacterial symbiont of Steinernema scapterisci nematodes, which is a cricket-specialist parasite and together the nematode and bacteria infect and kill crickets. Curiously, X. innexi expresses a potent extracellular mosquitocidal toxin activity in culture supernatants. We sequenced a draft genome of X. innexi and compared it to the genomes of related pathogens to elucidate the nature of specialization. RESULTS Using green fluorescent protein-expressing X. innexi we confirm previous reports using culture-dependent techniques that X. innexi colonizes its nematode host at low levels (~3-8 cells per nematode), relative to other Xenorhabdus-Steinernema associations. We found that compared to the well-characterized entomopathogenic nematode symbiont X. nematophila, X. innexi fails to suppress the insect phenoloxidase immune pathway and is attenuated for virulence and reproduction in the Lepidoptera Galleria mellonella and Manduca sexta, as well as the dipteran Drosophila melanogaster. To assess if, compared to other Xenorhabdus spp., X. innexi has a reduced capacity to synthesize virulence determinants, we obtained and analyzed a draft genome sequence. We found no evidence for several hallmarks of Xenorhabdus spp. toxicity, including Tc and Mcf toxins. Similar to other Xenorhabdus genomes, we found numerous loci predicted to encode non-ribosomal peptide/polyketide synthetases. Anti-SMASH predictions of these loci revealed one, related to the fcl locus that encodes fabclavines and zmn locus that encodes zeamines, as a likely candidate to encode the X. innexi mosquitocidal toxin biosynthetic machinery, which we designated Xlt. In support of this hypothesis, two mutants each with an insertion in an Xlt biosynthesis gene cluster lacked the mosquitocidal compound based on HPLC/MS analysis and neither produced toxin to the levels of the wild type parent. CONCLUSIONS The X. innexi genome will be a valuable resource in identifying loci encoding new metabolites of interest, but also in future comparative studies of nematode-bacterial symbiosis and niche partitioning among bacterial pathogens.
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Affiliation(s)
- Il-Hwan Kim
- Department of Entomology, University of Wisconsin-Madison, Madison, WI USA
- Present address: Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, Rockville, MD USA
| | | | - Dariush T. Aghai
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI USA
| | | | - Kai Hillman
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI USA
| | - Michael P. Kozuch
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI USA
| | - Erin J. Mans
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI USA
- Department of Microbiology, University of Tennessee-Knoxville, Knoxville, TN USA
| | - Terra J. Mauer
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI USA
- Department of Microbiology, University of Tennessee-Knoxville, Knoxville, TN USA
| | | | - Jerald C. Ensign
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI USA
| | | | - Walter G. Goodman
- Department of Entomology, University of Wisconsin-Madison, Madison, WI USA
| | - Heidi Goodrich-Blair
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI USA
- Department of Microbiology, University of Tennessee-Knoxville, Knoxville, TN USA
| | - Adler R. Dillman
- Department of Nematology, University of California, Riverside, CA USA
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91
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The Role of Type VI Secretion System Effectors in Target Cell Lysis and Subsequent Horizontal Gene Transfer. Cell Rep 2017; 21:3927-3940. [DOI: 10.1016/j.celrep.2017.12.020] [Citation(s) in RCA: 74] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Revised: 11/22/2017] [Accepted: 12/05/2017] [Indexed: 01/13/2023] Open
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92
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Abstract
The type VI secretion system (T6SS) is a multiprotein complex widespread in Proteobacteria and dedicated to the delivery of toxins into both prokaryotic and eukaryotic cells. It thus participates in interbacterial competition as well as pathogenesis. The T6SS is a contractile weapon, related to the injection apparatus of contractile tailed bacteriophages. Basically, it assembles an inner tube wrapped by a sheath-like structure and anchored to the cell envelope via a membrane complex. The energy released by the contraction of the sheath propels the inner tube through the membrane channel and toward the target cell. Although the assembly and the mechanism of action are conserved across species, the repertoire of secreted toxins and the diversity of the regulatory mechanisms and of target cells make the T6SS a highly versatile secretion system. The T6SS is particularly represented in Escherichia coli pathotypes and Salmonella serotypes. In this review we summarize the current knowledge regarding the prevalence, the assembly, the regulation, and the roles of the T6SS in E. coli, Salmonella, and related species.
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93
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Ray A, Schwartz N, de Souza Santos M, Zhang J, Orth K, Salomon D. Type VI secretion system MIX-effectors carry both antibacterial and anti-eukaryotic activities. EMBO Rep 2017; 18:1978-1990. [PMID: 28912123 PMCID: PMC5666596 DOI: 10.15252/embr.201744226] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Revised: 08/14/2017] [Accepted: 08/16/2017] [Indexed: 12/12/2022] Open
Abstract
Most type VI secretion systems (T6SSs) described to date are protein delivery apparatuses that mediate bactericidal activities. Several T6SSs were also reported to mediate virulence activities, although only few anti-eukaryotic effectors have been described. Here, we identify three T6SSs in the marine bacterium Vibrio proteolyticus and show that T6SS1 mediates bactericidal activities under warm marine-like conditions. Using comparative proteomics, we find nine potential T6SS1 effectors, five of which belong to the polymorphic MIX-effector class. Remarkably, in addition to six predicted bactericidal effectors, the T6SS1 secretome includes three putative anti-eukaryotic effectors. One of these is a MIX-effector containing a cytotoxic necrotizing factor 1 domain. We demonstrate that T6SS1 can use this MIX-effector to target phagocytic cells, resulting in morphological changes and actin cytoskeleton rearrangements. In conclusion, the V. proteolyticus T6SS1, a system homologous to one found in pathogenic vibrios, uses a suite of polymorphic effectors that target both bacteria and eukaryotic neighbors.
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Affiliation(s)
- Ann Ray
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Nika Schwartz
- Department of Clinical Microbiology and Immunology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Marcela de Souza Santos
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Junmei Zhang
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Kim Orth
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Dor Salomon
- Department of Clinical Microbiology and Immunology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
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94
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Bleves S. Don't judge a book by its cover: The Hcps are not only structural components of the T6SS machinery. Virulence 2017; 8:1053-1054. [PMID: 28277899 DOI: 10.1080/21505594.2017.1295908] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Affiliation(s)
- Sophie Bleves
- a Aix-Marseille Univ, CNRS, LISM UMR7255, IMM (Institut de Microbiologie de la Méditerranée) , Marseille , France
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95
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Olson RM, Anderson DM. Usurping bacterial virulence factors as self-delivery vehicles for therapeutic use. Virulence 2017. [PMID: 28636422 DOI: 10.1080/21505594.2017.1336595] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
Affiliation(s)
- Rachel M Olson
- a Department of Veterinary Pathobiology and the Laboratory for Infectious Disease Research , University of Missouri , Columbia , MO11 , USA
| | - Deborah M Anderson
- a Department of Veterinary Pathobiology and the Laboratory for Infectious Disease Research , University of Missouri , Columbia , MO11 , USA
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96
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Gao X, Mu Z, Qin B, Sun Y, Cui S. Structure-Based Prototype Peptides Targeting the Pseudomonas aeruginosa Type VI Secretion System Effector as a Novel Antibacterial Strategy. Front Cell Infect Microbiol 2017; 7:411. [PMID: 28979890 PMCID: PMC5611513 DOI: 10.3389/fcimb.2017.00411] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2017] [Accepted: 09/05/2017] [Indexed: 12/20/2022] Open
Abstract
The type VI secretion system (T6SS) secretes numerous toxins for bacteria-bacteria competition. TplE is a newly identified trans-kingdom toxin secreted by the T6SS in Pseudomonas aeruginosa, while TplEi neutralizes the toxic effect of TplE to protect bacteria autointoxication. Blocking the interaction of TplE-TplEi could unleash the toxin, causing bacterial cell death. In this study, we applied a crystallographic approach to design a structural-based antimicrobial peptides targeting the interaction of TplE and TplEi. We found that a peptide (designed as “L” peptide based on its shape) derived from TplE can form a crystal complex with TplEi after subtilisin treatment and the crystal structure was solved at 2.2Å. The “L” peptide displays strong binding affinity to TplEi in vitro and can release the TplE toxin to induce bacteria death in vivo. Our findings suggest that as a toxin activator, the “L” peptide could be a possible drug lead for treating P. aeruginosa infection. Our findings provide an example that the T6SS effector and immunity protein could be a potential drug target against bacteria infection.
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Affiliation(s)
- Xiaopan Gao
- MOH Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology, Chinese Academy of Medical Sciences and Peking Union Medical CollegeBeijing, China
| | - Zhixia Mu
- MOH Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology, Chinese Academy of Medical Sciences and Peking Union Medical CollegeBeijing, China
| | - Bo Qin
- MOH Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology, Chinese Academy of Medical Sciences and Peking Union Medical CollegeBeijing, China
| | - Yicheng Sun
- MOH Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology, Chinese Academy of Medical Sciences and Peking Union Medical CollegeBeijing, China
| | - Sheng Cui
- MOH Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology, Chinese Academy of Medical Sciences and Peking Union Medical CollegeBeijing, China
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97
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Brackmann M, Nazarov S, Wang J, Basler M. Using Force to Punch Holes: Mechanics of Contractile Nanomachines. Trends Cell Biol 2017; 27:623-632. [DOI: 10.1016/j.tcb.2017.05.003] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Revised: 05/10/2017] [Accepted: 05/12/2017] [Indexed: 12/25/2022]
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98
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Zoued A, Durand E, Santin YG, Journet L, Roussel A, Cambillau C, Cascales E. TssA: The cap protein of the Type VI secretion system tail. Bioessays 2017; 39. [DOI: 10.1002/bies.201600262] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Abdelrahim Zoued
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie de la Méditerranée (IMM); Aix-Marseille Université - CNRS; Marseille France
| | - Eric Durand
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie de la Méditerranée (IMM); Aix-Marseille Université - CNRS; Marseille France
| | - Yoann G. Santin
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie de la Méditerranée (IMM); Aix-Marseille Université - CNRS; Marseille France
| | - Laure Journet
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie de la Méditerranée (IMM); Aix-Marseille Université - CNRS; Marseille France
| | - Alain Roussel
- Architecture et Fonction des Macromolécules Biologiques; Centre National de la Recherche Scientifique; Marseille France
- Architecture et Fonction des Macromolécules Biologiques; Aix-Marseille Université; Marseille France
| | - Christian Cambillau
- Architecture et Fonction des Macromolécules Biologiques; Centre National de la Recherche Scientifique; Marseille France
- Architecture et Fonction des Macromolécules Biologiques; Aix-Marseille Université; Marseille France
| | - Eric Cascales
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie de la Méditerranée (IMM); Aix-Marseille Université - CNRS; Marseille France
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99
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Abstract
Horizontal gene transfer (HGT) can have profound effects on bacterial evolution by allowing individuals to rapidly acquire adaptive traits that shape their strategies for competition. One strategy for intermicrobial antagonism often used by Proteobacteria is the genetically encoded contact-dependent type VI secretion system (T6SS), a weapon used to kill heteroclonal neighbors by direct injection of toxic effectors. Here, we experimentally demonstrate that Vibrio cholerae can acquire new T6SS effector genes via horizontal transfer and utilize them to kill neighboring cells. Replacement of one or more parental alleles with novel effectors allows the recombinant strain to dramatically outcompete its parent. Using spatially explicit modeling, we examine how this process could affect the ecology and evolution of surface-attached microbial populations. HGT of T6SS effector-immunity pairs is risky: transformation brings a cell into conflict with its former clone mates but can be adaptive when superior T6SS alleles are acquired. More generally, we find that these costs and benefits are not symmetric and that high rates of HGT can act as a hedge against competitors with unpredictable T6SS efficacy. We conclude that antagonism and horizontal transfer drive successive rounds of weapon optimization and selective sweeps, dynamically shaping the composition of microbial communities. The contact-dependent type VI secretion system (T6SS) is frequently used by Proteobacteria to kill adjacent competitors. While DNA released by T6 killing can be horizontally acquired, it remains untested whether T6 genes themselves can be horizontally acquired and then utilized to compete with neighboring cells. Using naturally transformable Vibrio cholerae, we provide the first direct empirical support for the hypothesis that T6 genes are exchanged horizontally (e.g., from dead competitors) and functionally deployed to compete with neighboring cells. Using computational simulations, we also demonstrate that high rates of HGT can be adaptive, allowing V. cholerae to improve upon existing T6 weaponry and survive direct encounters with otherwise superior competitors. We anticipate that our evolutionary results are of broad microbiological relevance, applying to many bacteria capable of HGT that utilize the T6SS or similar antagonistic systems, and highlight the profound impact of HGT in shaping microbial community structure.
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Arming the Neighborhood. Dev Cell 2017; 39:5-6. [PMID: 27728781 DOI: 10.1016/j.devcel.2016.09.024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Bacteria use type 6 secretion systems in antagonistic behavior to compete for resources with other bacteria. In a recent issue of Cell, Vettiger and Basler (2016) show that bacteria can also use these systems to arm neighboring cells and force them to pass on a signal in the bacterial population.
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