Xiong Caijiang, Jiao Hanyang, Ran Jiayan, Li Detao, Li Ziyang, Wang Bei, Luo Hui, Li Yun, Lin Ying, Yao Jiayun, Wu Ronghua
Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City & Aquaculture Engineering Technology Research Center, College of Fisheries, Southwest University, Chongqing 400715, China.
The first affiliated hospital of Chongqing medical university, Chongqing 400042, China.
Int J Biol Macromol. 2025 Jan;284(Pt 1):138080. doi: 10.1016/j.ijbiomac.2024.138080. Epub 2024 Nov 26.
Aeromonas hydrophila is a serious human and animal co-pathogenic bacterium. The type II secretion system (T2SS), a key virulence factor, is vital for the secretion of exotoxins from the bacterium. exeA gene is important for the assembly of the T2SS. However, the role of exeA in the pathogenesis of A. hydrophila is not yet clear. In this study, we constructed a stable A. hydrophila strain with exeA mutation (∆exeA-AH) using homologous recombination. Compared to wild type A. hydrophila (WT-AH), the median lethal doses (LD) significantly increased in ∆exeA-AH. Biological properties of ∆exeA-AH were analyzed to explain the reasons for changes in virulence. The results showed that there was a significant decline in biofilm formation capacity, no significant differences were found in growth ability, hemolytic activity, motility and external structure. In order to further investigate the molecular mechanism of decreased virulence, WT-AH and ∆exeA-AH were subjected to transcriptomic analysis and validated by realtime fluorescence quantitative polymerase chain reaction and western blot. The results showed that the mutation of exeA affected the assembly of T2SS and biofilm formation capacity by decreasing the uptake capacity of iron ions. However, the abilities of T6SS, Sec system, Tat system, signaling peptidase and Lol system were enhanced, hindering further reduction in virulence. In summary, exeA mutation led to a reduction in virulence by impairing the function of T2SS and the ability of biofilm formation but impeded further decline by enhancing T6SS, Sec system, Tat system, signaling peptidase and Lol system.
嗜水气单胞菌是一种严重的人畜共患病原菌。II型分泌系统（T2SS）作为关键的毒力因子，对该菌外毒素的分泌至关重要。exeA基因对T2SS的组装很重要。然而，exeA在嗜水气单胞菌致病机制中的作用尚不清楚。在本研究中，我们利用同源重组构建了一株exeA基因发生突变的稳定嗜水气单胞菌菌株（∆exeA-AH）。与野生型嗜水气单胞菌（WT-AH）相比，∆exeA-AH的半数致死剂量（LD）显著增加。分析了∆exeA-AH的生物学特性，以解释其毒力变化的原因。结果表明，其生物膜形成能力显著下降，而生长能力、溶血活性、运动性和外部结构未发现显著差异。为了进一步探究毒力降低的分子机制，对WT-AH和∆exeA-AH进行了转录组分析，并通过实时荧光定量聚合酶链反应和蛋白质免疫印迹进行验证。结果表明，exeA突变通过降低铁离子摄取能力影响T2SS的组装和生物膜形成能力。然而，VI型分泌系统（T6SS）、Sec系统、Tat系统、信号肽酶和Lol系统的能力增强，阻碍了毒力的进一步降低。综上所述，exeA突变通过损害T2SS功能和生物膜形成能力导致毒力降低，但通过增强T6SS、Sec系统、Tat系统、信号肽酶和Lol系统阻碍了毒力的进一步下降。
