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Wu CF, Smith DA, Lai EM, Chang JH. The Agrobacterium Type VI Secretion System: A Contractile Nanomachine for Interbacterial Competition. Curr Top Microbiol Immunol 2018; 418:215-231. [PMID: 29992360 DOI: 10.1007/82_2018_99] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The bacterial type VI secretion system (T6SS) is a contractile nanomachine dedicated to delivering molecules out of bacterial cells. T6SS-encoding loci are in the genome sequences of many Gram-negative bacteria, and T6SS has been implicated in a plethora of roles. In the majority of cases, the T6SSs deliver effector proteins in a contact-dependent manner to antagonize other bacteria. Current models suggest that the effectors are deployed to influence social interactions in microbial communities. In this chapter, we describe the structure, function, and regulation of the T6SS and its effectors. We provide focus on the T6SS of Agrobacterium tumefaciens, the causative agent of crown gall disease, and relate the role of the T6SS to the ecology of A. tumefaciens.
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Affiliation(s)
- Chih-Feng Wu
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR, USA
| | - Delaney A Smith
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR, USA
| | - Erh-Min Lai
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei, 11529, Taiwan
| | - Jeff H Chang
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR, USA.
- Center for Genome Research and Biocomputing, Oregon State University, Corvallis, OR, USA.
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Bernal P, Llamas MA, Filloux A. Type VI secretion systems in plant-associated bacteria. Environ Microbiol 2017; 20:1-15. [PMID: 29027348 PMCID: PMC5813230 DOI: 10.1111/1462-2920.13956] [Citation(s) in RCA: 132] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2017] [Revised: 10/02/2017] [Accepted: 10/05/2017] [Indexed: 11/28/2022]
Abstract
The type VI secretion system (T6SS) is a bacterial nanomachine used to inject effectors into prokaryotic or eukaryotic cells and is thus involved in both host manipulation and interbacterial competition. The T6SS is widespread among Gram‐negative bacteria, mostly within the Proteobacterium Phylum. This secretion system is commonly found in commensal and pathogenic plant‐associated bacteria. Phylogenetic analysis of phytobacterial T6SS clusters shows that they are distributed in the five main clades previously described (group 1–5). The even distribution of the system among commensal and pathogenic phytobacteria suggests that the T6SS provides fitness and colonization advantages in planta and that the role of the T6SS is not restricted to virulence. This manuscript reviews the phylogeny and biological roles of the T6SS in plant‐associated bacteria, highlighting a remarkable diversity both in terms of mechanism and function.
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Affiliation(s)
- Patricia Bernal
- Department of Life Sciences, MRC Centre for Molecular Bacteriology and Infection, Flowers Building, 1st floor South Kensington Campus, Imperial College London, London SW7 2AZ, UK
| | - María A Llamas
- Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, 18008 Granada, Spain
| | - Alain Filloux
- Department of Life Sciences, MRC Centre for Molecular Bacteriology and Infection, Flowers Building, 1st floor South Kensington Campus, Imperial College London, London SW7 2AZ, UK
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Park JM, You YH, Park JH, Kim HH, Ghim SY, Back CG. Cutaneous Microflora from Geographically Isolated Groups of Bradysia agrestis, an Insect Vector of Diverse Plant Pathogens. MYCOBIOLOGY 2017; 45:160-171. [PMID: 29138620 PMCID: PMC5673511 DOI: 10.5941/myco.2017.45.3.160] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Revised: 06/15/2017] [Accepted: 07/03/2017] [Indexed: 06/07/2023]
Abstract
Larvae of Bradysia agrestis, an insect vector that transports plant pathogens, were sampled from geographically isolated regions in Korea to identify their cutaneous fungal and bacterial flora. Sampled areas were chosen within the distribution range of B. agrestis; each site was more than 91 km apart to ensure geographical segregation. We isolated 76 microbial (fungi and bacteria) strains (site 1, 29; site 2, 29; site 3, 18 strains) that were identified on the basis of morphological differences. Species identification was molecularly confirmed by determination of universal fungal internal transcribed spacer and bacterial 16S rRNA gene sequences in comparison to sequences in the EzTaxon database and the NCBI GenBank database, and their phylogenetic relationships were determined. The fungal isolates belonged to 2 phyla, 5 classes, and 7 genera; bacterial species belonged to 23 genera and 32 species. Microbial diversity differed significantly among the geographical groups with respect to Margalef's richness (3.9, 3.6, and 4.5), Menhinick's index (2.65, 2.46, and 3.30), Simpson's index (0.06, 0.12, and 0.01), and Shannon's index (2.50, 2.17, and 2.58). Although the microbial genera distribution or diversity values clearly varied among geographical groups, common genera were identified in all groups, including the fungal genus Cladosporium, and the bacterial genera Bacillus and Rhodococcus. According to classic principles of co-evolutionary relationship, these genera might have a closer association with their host insect vector B. agrestis than other genera identified. Some cutaneous bacterial genera (e.g., Pseudomonas) displaying weak interdependency with insect vectors may be hazardous to agricultural environments via mechanical transmission via B. agrestis. This study provides comprehensive information regarding the cutaneous microflora of B. agrestis, which can help in the control of such pests for crop management.
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Affiliation(s)
- Jong Myong Park
- School of Life Sciences, BK21 Plus KNU Creative BioResearch Group, Institute for Microorganisms, Kyungpook National University, Daegu 41566, Korea
| | - Young-Hyun You
- Microorganism Resources Division, National Institute of Biological Resources, Incheon 22689, Korea
| | - Jong-Han Park
- Horticultural & Herbal Crop Environment Division, National Institute of Horticultural & Herbal Science, Rural Development Administration, Wanju 55365, Korea
| | - Hyeong-Hwan Kim
- Horticultural & Herbal Crop Environment Division, National Institute of Horticultural & Herbal Science, Rural Development Administration, Wanju 55365, Korea
| | - Sa-Youl Ghim
- School of Life Sciences, BK21 Plus KNU Creative BioResearch Group, Institute for Microorganisms, Kyungpook National University, Daegu 41566, Korea
| | - Chang-Gi Back
- Horticultural & Herbal Crop Environment Division, National Institute of Horticultural & Herbal Science, Rural Development Administration, Wanju 55365, Korea
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Gallique M, Bouteiller M, Merieau A. The Type VI Secretion System: A Dynamic System for Bacterial Communication? Front Microbiol 2017; 8:1454. [PMID: 28804481 PMCID: PMC5532429 DOI: 10.3389/fmicb.2017.01454] [Citation(s) in RCA: 94] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Accepted: 07/18/2017] [Indexed: 11/13/2022] Open
Abstract
Numerous studies in Gram-negative bacteria have focused on the Type VISecretion Systems (T6SSs), Quorum Sensing (QS), and social behavior, such as in biofilms. These interconnected mechanisms are important for bacterial survival; T6SSs allow bacteria to battle other cells, QS is devoted to the perception of bacterial cell density, and biofilm formation is essentially controlled by QS. Here, we review data concerning T6SS dynamics and T6SS–QS cross-talk that suggest the existence of inter-bacterial communication via T6SSs.
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Affiliation(s)
- Mathias Gallique
- Laboratoire de Microbiologie Signaux et Microenvironnement EA 4312, l'Institut Universitaire de Technologie d'Evreux (IUT), Université de Rouen, Normandy UniversityEvreux, France
| | - Mathilde Bouteiller
- Laboratoire de Microbiologie Signaux et Microenvironnement EA 4312, l'Institut Universitaire de Technologie d'Evreux (IUT), Université de Rouen, Normandy UniversityEvreux, France
| | - Annabelle Merieau
- Laboratoire de Microbiologie Signaux et Microenvironnement EA 4312, l'Institut Universitaire de Technologie d'Evreux (IUT), Université de Rouen, Normandy UniversityEvreux, France
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Lien YW, Lai EM. Type VI Secretion Effectors: Methodologies and Biology. Front Cell Infect Microbiol 2017; 7:254. [PMID: 28664151 PMCID: PMC5471719 DOI: 10.3389/fcimb.2017.00254] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Accepted: 05/31/2017] [Indexed: 12/26/2022] Open
Abstract
The type VI secretion system (T6SS) is a nanomachine deployed by many Gram-negative bacteria as a weapon against eukaryotic hosts or prokaryotic competitors. It assembles into a bacteriophage tail-like structure that can transport effector proteins into the environment or target cells for competitive survival or pathogenesis. T6SS effectors have been identified by a variety of approaches, including knowledge/hypothesis-dependent and discovery-driven approaches. Here, we review and discuss the methods that have been used to identify T6SS effectors and the biological and biochemical functions of known effectors. On the basis of the nature and transport mechanisms of T6SS effectors, we further propose potential strategies that may be applicable to identify new T6SS effectors.
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Affiliation(s)
- Yun-Wei Lien
- Institute of Plant and Microbial Biology, Academia SinicaTaipei, Taiwan.,Department of Plant Pathology and Microbiology, National Taiwan UniversityTaipei, Taiwan
| | - Erh-Min Lai
- Institute of Plant and Microbial Biology, Academia SinicaTaipei, Taiwan.,Department of Plant Pathology and Microbiology, National Taiwan UniversityTaipei, Taiwan
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A Pseudomonas T6SS effector recruits PQS-containing outer membrane vesicles for iron acquisition. Nat Commun 2017; 8:14888. [PMID: 28348410 PMCID: PMC5379069 DOI: 10.1038/ncomms14888] [Citation(s) in RCA: 202] [Impact Index Per Article: 28.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Accepted: 02/09/2017] [Indexed: 01/20/2023] Open
Abstract
Iron sequestration by host proteins contributes to the defence against bacterial pathogens, which need iron for their metabolism and virulence. A Pseudomonas aeruginosa mutant lacking all three known iron acquisition systems retains the ability to grow in media containing iron chelators, suggesting the presence of additional pathways involved in iron uptake. Here we screen P. aeruginosa mutants defective in growth in iron-depleted media and find that gene PA2374, proximal to the type VI secretion system H3 (H3-T6SS), functions synergistically with known iron acquisition systems. PA2374 (which we have renamed TseF) appears to be secreted by H3-T6SS and is incorporated into outer membrane vesicles (OMVs) by directly interacting with the iron-binding Pseudomonas quinolone signal (PQS), a cell–cell signalling compound. TseF facilitates the delivery of OMV-associated iron to bacterial cells by engaging the Fe(III)-pyochelin receptor FptA and the porin OprF. Our results reveal links between type VI secretion, cell–cell signalling and classic siderophore receptors for iron acquisition in P. aeruginosa. Pathogens require iron for their metabolism and virulence. Here the authors identify an iron acquisition system in Pseudomonas aeruginosa involving a protein secreted by a type VI secretion system, the PQS signalling compound and siderophore receptors.
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Manganese scavenging and oxidative stress response mediated by type VI secretion system in Burkholderia thailandensis. Proc Natl Acad Sci U S A 2017; 114:E2233-E2242. [PMID: 28242693 DOI: 10.1073/pnas.1614902114] [Citation(s) in RCA: 162] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Type VI secretion system (T6SS) is a versatile protein export machinery widely distributed in Gram-negative bacteria. Known to translocate protein substrates to eukaryotic and prokaryotic target cells to cause cellular damage, the T6SS has been primarily recognized as a contact-dependent bacterial weapon for microbe-host and microbial interspecies competition. Here we report contact-independent functions of the T6SS for metal acquisition, bacteria competition, and resistance to oxidative stress. We demonstrate that the T6SS-4 in Burkholderia thailandensis is critical for survival under oxidative stress and is regulated by OxyR, a conserved oxidative stress regulator. The T6SS-4 is important for intracellular accumulation of manganese (Mn2+) under oxidative stress. Next, we identified a T6SS-4-dependent Mn2+-binding effector TseM, and its interacting partner MnoT, a Mn2+-specific TonB-dependent outer membrane transporter. Similar to the T6SS-4 genes, expression of mnoT is regulated by OxyR and is induced under oxidative stress and low Mn2+ conditions. Both TseM and MnoT are required for efficient uptake of Mn2+ across the outer membrane under Mn2+-limited and -oxidative stress conditions. The TseM-MnoT-mediated active Mn2+ transport system is also involved in contact-independent bacteria-bacteria competition and bacterial virulence. This finding provides a perspective for understanding the mechanisms of metal ion uptake and the roles of T6SS in bacteria-bacteria competition.
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Molina L, Geoffroy VA, Segura A, Udaondo Z, Ramos JL. Iron Uptake Analysis in a Set of Clinical Isolates of Pseudomonas putida. Front Microbiol 2016; 7:2100. [PMID: 28082966 PMCID: PMC5187384 DOI: 10.3389/fmicb.2016.02100] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Accepted: 12/12/2016] [Indexed: 11/13/2022] Open
Abstract
Pseudomonas putida strains are frequent inhabitants of soil and aquatic niches and they are occasionally isolated from hospital environments. As the available iron sources in human tissues, edaphic, and aquatic niches are different, we have analyzed iron-uptake related genes in different P. putida strains that were isolated from all these environments. We found that these isolates can be grouped into different clades according to the genetics of siderophore biosynthesis and recycling. The pyoverdine locus of the six P. putida clinical isolates that have so far been completely sequenced, are not closely related; three strains (P. putida HB13667, HB3267, and NBRC14164T) are grouped in Clade I and the other three in Clade II, suggesting possible different origins and evolution. In one clinical strain, P. putida HB4184, the production of siderophores is induced under high osmolarity conditions. The pyoverdine locus in this strain is closely related to that of strain P. putida HB001 which was isolated from sandy shore soil of the Yellow Sea in Korean marine sand, suggesting their possible origin, and evolution. The acquisition of two unique TonB-dependent transporters for xenosiderophore acquisition, similar to those existing in the opportunistic pathogen P. aeruginosa PAO, is an interesting adaptation trait of the clinical strain P. putida H8234 that may confer adaptive advantages under low iron availability conditions.
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Affiliation(s)
- Lázaro Molina
- Environmental Protection Department, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas Granada, Spain
| | - Valérie A Geoffroy
- Centre National de la Recherche Scientifique, UMR 7242, Université de Strasbourg, (ESBS) Illkirch, France
| | - Ana Segura
- Environmental Protection Department, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas Granada, Spain
| | - Zulema Udaondo
- Environmental Protection Department, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas Granada, Spain
| | - Juan-Luis Ramos
- Environmental Protection Department, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas Granada, Spain
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