State Key Laboratory of Developmental Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, 410081, P. R. China.
Arch Microbiol. 2024 Aug 17;206(9):381. doi: 10.1007/s00203-024-04101-5.
The bacterial type II toxin-antitoxin (TA) system is a rich genetic element that participates in various physiological processes. Aeromonas veronii is the main bacterial pathogen threatening the freshwater aquaculture industry. However, the distribution of type II TA system in A. veronii was seldom documented and its roles in the life activities of A. veronii were still unexplored. In this study, a novel type II TA system AvtA-AvtT was predicted in a fish pathogen Aeromonas veronii biovar sobria with multi-drug resistance using TADB 2.0. Through an Escherichia coli host killing and rescue assay, we demonstrated that AvtA and AvtT worked as a genuine TA system, and the predicted toxin AvtT actually functioned as an antitoxin while the predicted antitoxin AvtA actually functioned as a toxin. The binding ability of AvtA with AvtT proteins were confirmed by dot blotting analysis and co-immunoprecipitation assay. Furthermore, we found that the toxin and antitoxin labelled with fluorescent proteins were co-localized. In addition, it was found that the transcription of AvtAT bicistronic operon was repressed by the AvtAT protein complex. Deletion of avtA gene and avtT gene had no obvious effect on the drug susceptibility. This study provides first characterization of type II TA system AvtA-AvtT in aquatic pathogen A. veronii.
细菌 II 型毒素-抗毒素（TA）系统是一种丰富的遗传元件，参与多种生理过程。维氏气单胞菌是威胁淡水水产养殖业的主要细菌病原体。然而，II 型 TA 系统在维氏气单胞菌中的分布很少被记录，其在维氏气单胞菌生命活动中的作用仍未被探索。在本研究中，使用 TADB 2.0 在具有多药耐药性的鱼类病原体维氏气单胞菌亚种中预测了一种新型 II 型 TA 系统 AvtA-AvtT。通过大肠杆菌宿主杀伤和拯救实验，我们证明 AvtA 和 AvtT 作为一个真正的 TA 系统发挥作用，预测的毒素 AvtT 实际上作为抗毒素发挥作用，而预测的抗毒素 AvtA 实际上作为毒素发挥作用。AvtA 与 AvtT 蛋白的结合能力通过点印迹分析和共免疫沉淀实验得到证实。此外，我们发现标记有荧光蛋白的毒素和抗毒素发生共定位。此外，还发现 AvtAT 双顺反子操纵子的转录受到 AvtAT 蛋白复合物的抑制。avtA 基因和 avtT 基因的缺失对药物敏感性没有明显影响。本研究首次对水生病原体维氏气单胞菌中的 II 型 TA 系统 AvtA-AvtT 进行了表征。
