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Type vi secretion system

Anoop Alex, Agostinho Antunes
Bacteria belonging to the genus Pseudovibrio have been frequently found in association with a wide variety of marine eukaryotic invertebrate hosts, indicative of their versatile and symbiotic lifestyle. A recent comparison of the sponge-associated Pseudovibrio genomes has shed light on the mechanisms influencing a successful symbiotic association with sponges. In contrast, the genomic architecture of Pseudovibrio bacteria associated with other marine hosts has received less attention. Here, we performed genus-wide comparative analyses of 18 Pseudovibrio isolated from sponges, coral, tunicates, flatworm, and seawater...
2018: PloS One
Yin-Yin Hu, Cai-Xia Liu, Peng Liu, Zhuo-Ying Wu, Ya-Dong Zhang, Xiao-Shun Xiong, Xiang-Yang Li
PURPOSE: The objective of the current study was to investigate whether hcp plays a role in the process of Acinetobacter baumannii infection and to examine clinically relevant factors that may affect hcp expression. METHODOLOGY: Seventy-seven A. baumannii isolates from patients with a respiratory infection at the Second Affiliated Hospital and Yuying Childrens Hospital of Wenzhou Medical University (Wenzhou, China) were included in this study. PCR was performed to screen for the presence of hcp...
May 17, 2018: Journal of Medical Microbiology
Xiaolong Shao, Xiaoning Zhang, Yingchao Zhang, Miao Zhu, Pan Yang, Jian Yuan, Yingpeng Xie, Tianhong Zhou, Wei Wang, Sheng Chen, Haihua Liang, Xin Deng
Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen of humans, particularly those with cystic fibrosis. As a global regulator, RpoN controls a group of virulence-related factors and quorum sensing (QS) genes in P. aeruginosa To further gain insights into the direct targets of RpoN in vivo , the present study focused on identifying the direct targets of RpoN regulation in QS and the type VI secretion system (T6SS). We performed a chromatin immunoprecipitation coupled to high-throughput sequencing (ChIP-seq) assay that identified 1,068 binding sites of RpoN, mostly including metabolic genes, a group of genes in QS ( lasI , rhlI and pqsR ) and the T6SS ( hcpA and hcpB )...
May 14, 2018: Journal of Bacteriology
Daniel L Clemens, Bai-Yu Lee, Marcus A Horwitz
Francisella tularensisis subsp. tularensis is an intracellular bacterial pathogen and the causative agent of the life-threatening zoonotic disease tularemia. The Francisella Pathogenicity Island encodes a large secretion apparatus, known as a Type VI Secretion System (T6SS), which is essential for Francisella to escape from its phagosome and multiply within host macrophages and to cause disease in animals. The T6SS, found in one-quarter of Gram-negative bacteria including many highly pathogenic ones, is a recently discovered secretion system that is not yet fully understood...
2018: Frontiers in Cellular and Infection Microbiology
Timothy C Fitzsimons, Jessica M Lewis, Amy Wright, Oded Kleifeld, Ralf B Schittenhelm, David Powell, Marina Harper, John D Boyce
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 non-covalently 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...
May 7, 2018: Infection and Immunity
Xiaobing Yang, Mingxiu Long, Xihui Shen
Type VI protein secretion systems (T6SSs) are specialized transport apparatus which can target both eukaryotic and prokaryotic cells and play key roles in host⁻pathogen⁻microbiota interactions. Therefore, T6SSs have attracted much attention as a research topic during the past ten years. In this review, we particularly summarized the T6SS antibacterial function, which involves an interesting offensive and defensive mechanism of the effector⁻immunity (E⁻I) pairs. The three main categories of effectors that target the cell wall, membranes, and nucleic acids during bacterial interaction, along with their corresponding immunity proteins are presented...
April 26, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Kyunglee Lee, Hye Kwon Kim, Sung-Kyun Park, Hawsun Sohn, Yuna Cho, Young-Min Choi, Dae Gwin Jeong, Ji Hyung Kim
Although several Edwardsiella tarda infections have been reported, its pathogenic role in marine mammals has not been investigated at the genome level. We investigated the genome of E. tarda strain KC-Pc-HB1, isolated from the false killer whale (Pseudorca crassidens) found bycaught in South Korea. The obtained genome was similar to that of human pathogenic E. tarda strains, but distinct from other Edwardsiella species. Although type III and VI secretion systems, which are essential for the virulence of other Edwardsiella species, were absent, several virulence-related genes involved in the pathogenesis of E...
April 25, 2018: Journal of Veterinary Medical Science
Jiale Ma, Min Sun, Zihao Pan, Chengping Lu, Huochun Yao
The type VI secretion system (T6SS) is considered as one of the key competition strategies by injecting toxic effectors for intestinal pathogens to acquire optimal colonization in host gut, a microenviroment with high-density polymicrobial community where bacteria compete for niches and resources. Enterotoxigenic Escherichia coli (ETEC), a major cause of infectious diarrhea in human and animals, widely encode T6SS clusters in their genomes. In this report, we first identified VT1, a novel amidase effector in ETEC, significantly hydrolyzed D-lactyl-L-Ala crosslinks between N-acetylmuramoyl and L-Ala in peptidoglycan...
April 16, 2018: Biochimica et Biophysica Acta
Savannah L Logan, Jacob Thomas, Jinyuan Yan, Ryan P Baker, Drew S Shields, Joao B Xavier, Brian K Hammer, Raghuveer Parthasarathy
Host-associated microbiota help defend against bacterial pathogens; however, the mechanisms by which pathogens overcome this defense remain largely unknown. We developed a zebrafish model and used live imaging to directly study how the human pathogen Vibrio cholerae invades the intestine. The gut microbiota of fish monocolonized by symbiotic strain Aeromonas veronii was displaced by V. cholerae expressing its type VI secretion system (T6SS), a syringe-like apparatus that deploys effector proteins into target cells...
April 2, 2018: Proceedings of the National Academy of Sciences of the United States of America
Jer-Sheng Lin, Panayiota Pissaridou, Hsin-Hui Wu, Ming-Daw Tsai, Alain Filloux, Erh-Min Lai
The bacterial type VI secretion system (T6SS) delivers effectors into eukaryotic host cells or toxins into bacterial competitor for survival and fitness. The T6SS is positively regulated by the threonine phosphorylation pathway (TPP) and negatively by the T6SS-accessory protein TagF. Here, we studied the mechanisms underlying TagF-mediated T6SS repression in two distinct bacterial pathogens, Agrobacterium tumefaciens and Pseudomonas aeruginosa. We found that in A. tumefaciens, T6SS toxin secretion and T6SS-dependent antibacterial activity are suppressed by a two-domain chimeric protein consisting of TagF and PppA, a putative phosphatase...
March 29, 2018: Journal of Biological Chemistry
Jiale Ma, Min Sun, Zihao Pan, Wenchao Song, Chengping Lu, Huochun Yao
Type VI secretion systems (T6SSs) contribute to the pathogenicity of avian pathogenic Escherichia coli (APEC), one of the leading causative agents of sepsis and meningitis in poultry. The Hcp protein is a core component of the T6SS tail tube and acts as an exported receptor and a chaperone of effectors. In this study, four distinct Hcp types (Ia, Ib, IIa, and IIb) were designated in Gram-negative bacteria, three of which were widely distributed in APEC. We detected divergence in transcription levels among three hcp clusters in 50% duck serum and demonstrated that hcp1 was upregulated by relieving Fur repression...
March 29, 2018: Emerging Microbes & Infections
Zhen Yang, Xuetong Wang, Wensheng Xu, Mian Zhou, Yuanxing Zhang, Yue Ma, Qiyao Wang
Type VI secretion systems (T6SSs) are multi-protein secretory nano-machines that mediate inter-bacterial competition. Vibrio alginolyticus is an abundant gram-negative marine bacterium that efficiently kills other bacteria with its T6SS2. The V. alginolyticus T6SS2 gene cluster encodes a phosphatase, PppA, and a type II membrane-spanning Hanks-type threonine kinase, PpkA2, which have been implicated in the activation of T6S. Meanwhile, T6SS2 gene expression is under the control of quorum sensing. However, the role of PppA in T6SS2 activity is unclear...
April 2018: Microbiological Research
Jacqueline Corbitt, Jun Seok Yeo, C Ian Davis, Michele LeRoux, Paul A Wiggins
The Type VI Secretion System (T6SS) inhibits growth of neighboring bacterial cells through a contact-mediated mechanism. We describe a detailed characterization of the protein localization dynamics in the Pseudomonas aeruginosa T6SS. It has been proposed that Type VI secretion process is driven by a conformational-change induced contraction of the T6SS sheath. However, although the contraction of an optically resolvable TssBC sheath and the subsequent localization of ClpV are observed in Vibrio cholerae , coordinated assembly and disassembly of TssB and ClpV are observed without TssB contraction in P...
March 19, 2018: Journal of Bacteriology
Martha A Zepeda-Rivera, Christina C Saak, Karine A Gibbs
The bacterium Proteus mirabilis can communicate identity through the secretion of the self-identity protein, IdsD, via the type VI secretion (T6S) system. IdsD secretion is essential for self versus non-self recognition behaviors in these populations. Here we provide an answer to the unresolved question of how the activity of a T6S substrate, such as IdsD, is regulated before secretion. We demonstrate that IdsD is found in clusters that form independently of the T6S machinery and activity. We show that the protein IdsC, which is a member of the proposed DUF4123 chaperone family, is essential for the maintenance of these clusters as well as the IdsD protein itself...
March 19, 2018: Journal of Bacteriology
Jiawei Wang, Bingjiao Yang, André Leier, Tatiana T Marquez-Lago, Morihiro Hayashida, Andrea Rocker, Zhang Yanju, Tatsuya Akutsu, Kuo-Chen Chou, Richard A Strugnell, Jiangning Song, Trevor Lithgow
Motivation: Many Gram-negative bacteria use type VI secretion systems (T6SS) to export effector proteins into adjacent target cells. These secreted effectors (T6SEs) play vital roles in the competitive survival in bacterial populations, as well as pathogenesis of bacteria. Although various computational analyses have been previously applied to identify effectors secreted by certain bacterial species, there is no universal method available to accurately predict T6SS effector proteins from the growing tide of bacterial genome sequence data...
March 14, 2018: Bioinformatics
A Avilés-Reyes, I A Freires, J K Kajfasz, D Barbieri, J H Miller, J A Lemos, J Abranches
We report the whole genome sequence of the serotype e Cbm+ strain LAR01 of Streptococcus mutans, a dental pathogen frequently associated with extra-oral infections. The LAR01 genome is a single circular chromosome of 2.1 Mb with a GC content of 36.96%. The genome contains 15 phosphotransferase system gene clusters, seven cell wall-anchored (LPxTG) proteins, all genes required for the development of natural competence and genes coding for mutacins VI and K8. Interestingly, the cbm gene is genetically linked to a putative type VII secretion system that has been found in Mycobacteria and few other Gram-positive bacteria...
June 2018: Molecular Oral Microbiology
Jorge E Galán, Gabriel Waksman
Many bacteria have evolved specialized nanomachines with the remarkable ability to inject multiple bacterially encoded effector proteins into eukaryotic or prokaryotic cells. Known as type III, type IV, and type VI secretion systems, these machines play a central role in the pathogenic or symbiotic interactions between multiple bacteria and their eukaryotic hosts, or in the establishment of bacterial communities in a diversity of environments. Here we focus on recent progress elucidating the structure and assembly pathways of these machines...
March 8, 2018: Cell
Hsiao-Han Lin, Hsin-Mei Huang, Manda Yu, Erh-Min Lai, Hsiao-Lin Chien, Chi-Te Liu
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...
March 8, 2018: Molecular Plant-microbe Interactions: MPMI
Byungjin Byun, Kiran V Mahasenan, David A Dik, Daniel R Marous, Enrico Speri, Malika Kumarasiri, Jed F Fisher, Juan A Hermoso, Shahriar Mobashery
Lytic transglycosylases (LTs) catalyze the non-hydrolytic cleavage of the bacterial cell wall by an intramolecular transacetalization reaction. This reaction is critically and broadly important in modifications of the bacterial cell wall in the course of its biosynthesis, recycling, manifestation of virulence, insertion of structural entities such as the flagellum and the pili, among others. The first QM/MM analysis of the mechanism of reaction of an LT, that for the Escherichia coli MltE, is undertaken. The study reveals a conformational itinerary consistent with an oxocarbenium-like transition state, characterized by a pivotal role for the active-site glutamic acid in proton transfer...
March 7, 2018: Scientific Reports
Lingzhi Zhang, Zhiwei Jiang, Shan Fang, Yajun Huang, Dahai Yang, Qiyao Wang, Yuanxing Zhang, Qin Liu
Many bacterial pathogens inject effectors directly into host cells to target a variety of host cellular processes and promote bacterial dissemination and survival. Identifying the bacterial effectors and elucidating their functions are central to understanding the molecular pathogenesis of these pathogens. Edwardsiella piscicida is a pathogen with a wide host range, and very few of its effectors have been identified to date. Here, based on the genes significantly regulated by macrophage infection, we identified 25 intracellular translocation-positive candidate effectors, including all five previously reported effectors, namely EseG, EseJ, EseH, EseK, and EvpP...
2018: Frontiers in Cellular and Infection Microbiology
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