鳗弧菌VgrG的分泌途径及致病机制

The type VI secretion system (T6SS) widely exists in Gram-negative bacteria and plays a role in virulence and interaction with environment. VgrG (valine-glycine repeat G) is a secreted component and an effector of T6SS. Its C-terminal was demonstrated in several pathogens to exert a role in bacterial pathogenesis. Vibrio anguillarum is an important pathogen of aquatic animals, and we have previously identified five vgrG homologous genes in its genome. However, the functions of these VgrGs have not been determined yet. This study aims to analyze the secretion pathways of the VgrGs and characterize the functions of VgrGs of V. anguillarum in the pathogenesis. Firstly, we are to determine whether the VgrGs are secreted by the T6SS-dependent route. Secondly, the impacts of VgrGs and their C-extension terminals on the T6SS secretion function are to be determined. Finally, the roles of VgrGs and their C-extension terminals on the viurlence to be determined. The present study will give deeper understandings of the pathogenesis of V. anguillarum. We hope the relevant results will provide new strategy to control the vibriosis in aquaculture.

VI分泌系统（T6SS）广泛存在革兰氏阴性菌中，负责将细菌产生的效应蛋白分泌到细菌细胞外或运输到宿主细胞内，在细菌与宿主相互作用中发挥重要的作用。VgrG(缬氨酸-甘氨酸重复蛋白G)为T6SS的结构蛋白和分泌蛋白，在一些病原菌中具有致病功能。鳗弧菌是水生动物的重要病原菌，在前期研究中我们完成了一株鳗弧菌全基因组的测序工作，发现鳗弧菌有五个VgrG同源基因，在C端具有不同的结构域。目前鳗弧菌VgrG的分泌途径及功能未明确，本项目将研究鳗弧菌VgrG的分泌途径，分析VgrG及其C端结构对T6SS分泌功能的影响，明确它们与鳗弧菌致病力的关系，揭示VgrG的致病机制，为防控鳗弧菌病提供新的理论依据。

六型分泌系统（T6SS）是格兰氏阴性细菌主要的攻击和防御武器，输送效应蛋白到宿主细胞和原核细胞中，在细菌与宿主相互作用及环境适应方面发挥着重要的作用。VgrG（缬氨酸-甘氨酸重复蛋白G）是T6SS的结构蛋白，同时也是其重要的分泌蛋白，细胞体内的部分毒素效应蛋白通过直接或间接偶联方式与VgrG结合形成新的效应蛋白，通过T6SS分泌到胞外发挥作用。本项目首先对一株非致病性T6SS-1缺失株MHK3进行了全基因组测序，并与前期的强致病性菌株M3等进行了比较基因组分析，构建获得了MHK3 vgrG1和vgrG4的基因缺失株，对鳗弧菌vgrG基因进行了原核表达条件摸索。通过野生株和突变株生理表型和基因功能表达的对比，获得了vgrG对鳗弧菌T6SS的调控及致病力的影响。该项目通过对MHK3菌株的比较分析及vgrG的功能研究，为海水养殖病害防治提供新的理论基础。