鳄鱼源达卡气单胞菌PhoBR的毒力调控机制

达卡气单胞菌是气单胞菌中毒力最强的高危致病菌，其强毒机制推测与其高合成被膜和高表达毒力基因有关。由于磷代谢调节双组分系统PhoBR调控被膜等多种与该菌一致的致病因子，且phoB基因缺失可导致该菌明显弱毒，因而认为，以PhoBR为突破口，通过探究其在该菌中的毒力调控机制，对理解该菌的高强致病性具有重要价值。本项目将以鳄鱼源高致病性达卡气单胞菌为材料，通过对PhoBR调控的毒力基因鉴定，对PhoBR如何调控这些毒力基因高表达的分子机制探究，以及对PhoBR及其上调强毒基因的缺失突变毒力表型分析，以阐述PhoBR在达卡气单胞菌中的毒力调控机制，为揭示该菌强毒机制提供重要证据；进而通过对PhoBR及其上调强毒基因缺失突变株的免疫效果分析，以评价这些基因在该菌免疫防治中的潜在应用价值，为减少该菌在鳄鱼等野生动物保护、水产养殖、甚至在人类中的危害筛选有效的基因靶点和侯选弱毒疫苗。

Aeromonas dhakensis is the primary aeromonas that endangers crocodile conservation and aquaculture in south China. Our study found that PhoBR, a two-component phosphorous metabolism system, regulates bacterial virulence and has high value in the immune control of the bacteria. With PhoBR as the breakthrough point, therefore, by studying the pathogenesis regulation mechanism of the bacterium, explore to PhoBR and key Pho regulons as targets in attenuated vaccine, can provide key evidence to clarify the scientific question of the high pathogenicity in A. dhakensis, for the science problem of immune prevention with candidate vaccines, to reduce the diseases of this pathogen in the crocodile conservation and aquaculture. The research contents of this project include: identifing all virulence associated Pho regulon genes through ChIP-seq and RNA-seq etc by using the highly pathogenic A. dhakensis strains isolated from crocodiles. The transcriptional regulation of PhoBR on these genes was studied by RT-qPCR and EMSA etc, so as to elaborate the virulence regulation mechanism of PhoBR in A. dhakensis. Finally, mutation phenotype analysis and immune effect evaluation of PhoBR and key virulence associated Pho regulons (3-5) are performed to develop some effective candidate attenuated vaccines for the immune control of this bacterium in Crocodiles and aquaculture.This project will provide theoretical basis for the prevention and control of pneumonia and septicaemia in crocodile breeding caused by A.dhakensis.