School of Marine Science and Engineering, Qingdao Agricultural University, Qingdao, China.
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, China.
J Fish Dis. 2020 Oct;43(10):1145-1154. doi: 10.1111/jfd.13224. Epub 2020 Jul 27.
Aeromonas salmonicida is a gram-negative bacterium that is the causative agent of furunculosis. An A. salmonicida strain was isolated from diseased turbot (Scophthalmus maximus) with the sign of furunculosis from North China. Based on vapA gene, the strain was further classified as A. salmonicida subsp. masoucida RZ6S-1. Culturing RZ6S-1 strain at high temperature (28°C) obtained the virulence attenuated strain RZ6S. Genome sequence comparison between the two strains revealed the loss of the type IV secretion system (T4SS) and type III secretion system (T3SS) from the native plasmid pAsmB-1 and pAsmC-1 of wild-type strain RZ6S-1, respectively. Further study demonstrated that the wild-type strain RZ6S-1, but not its derivative mutant RZ6S, can stimulate apoptosis. Elevated protein level of cleaved caspase-3 was detected from epithelioma papulosum cyprinid (EPC) cells infected with wild-type strain RZ6S-1 as compared with that infected with RZ6S strain. Meanwhile, the invasion of the mutant strain RZ6S was about 17-fold higher than the wild-type strain RZ6S-1, suggesting that some protein(s) from A. salmonicida subsp. masoucida RZ6S-1 suppress its invasion. The RZ6S mutant strain was attenuated, since its LD is over 10,000 times higher compared to the wild-type strain as revealed in the turbot infection model.
迟钝爱德华氏菌是一种革兰氏阴性菌，是疖病的病原体。从中国北方患有疖病的大菱鲆（Scophthalmus maximus）中分离到一株迟钝爱德华氏菌菌株。基于 vapA 基因，该菌株进一步分类为迟钝爱德华氏菌亚种 masoucida RZ6S-1。在高温（28°C）下培养 RZ6S-1 菌株获得了毒力减弱的菌株 RZ6S。两株菌的基因组序列比较显示，野生型菌株 RZ6S-1 中的天然质粒 pAsmB-1 和 pAsmC-1 中的 IV 型分泌系统（T4SS）和 III 型分泌系统（T3SS）分别丢失。进一步的研究表明，野生型菌株 RZ6S-1 但不是其衍生的突变体 RZ6S 可以刺激细胞凋亡。与感染 RZ6S 菌株的上皮瘤细胞相比，感染野生型菌株 RZ6S-1 的上皮瘤细胞中 cleaved caspase-3 的蛋白水平升高。同时，突变株 RZ6S 的侵袭能力比野生型菌株 RZ6S-1 高约 17 倍，表明迟钝爱德华氏菌亚种 masoucida RZ6S-1 中的一些蛋白抑制了其侵袭。由于在大菱鲆感染模型中，突变株 RZ6S 的 LD 比野生型菌株高 10,000 倍以上，因此该突变株是减毒的。
