Nakayama Hitoshi, Tanaka Keisuke, Teramura Naoko, Hattori Shunji
a Department of Freshwater Fisheries , Wakayama Prefectural Fisheries Experimental Station , Wakayama , Japan.
b Nippi Research Institute of Biomatrix , Toride , Japan.
Biosci Biotechnol Biochem. 2016;80(1):135-44. doi: 10.1080/09168451.2015.1079477. Epub 2015 Sep 1.
The collagenase activity and the fpcol gene were examined in Flavobacterium psychrophilum isolates from cold-water disease (CWD)-affected ayu, Plecoglossus altivelis. Collagenase expression was closely related to the accumulated mortality of CWD-affected ayu. RT-qPCR and bacterial challenge experiments showed that F. psychrophilum ayu isolate WA-1 expressed the fpcol gene more actively and was more virulent than ayu isolate WA-2. The amago (Oncorhynchus masou) isolate WB-1, which possesses a pseudo-fpcol gene, was not harmful to ayu. Hitherto, the well-studied metalloproteases Fpp1 and Fpp2 have been considered virulence factors. However, the most virulent isolate against ayu (WA-1) showed no Fpp activity because of a deletion mutation or an insertion of a transposon in the fpp genes. The less virulent WA-2 isolate showed only Fpp1 activity. Taken together, these results suggest that collagenolytic activity, but not Fpp activity, is related to the virulence of F. psychrophilum isolates in CWD-affected ayu.
对从患冷水病（CWD）的香鱼（Plecoglossus altivelis）中分离出的嗜冷黄杆菌菌株检测了胶原酶活性和fpcol基因。胶原酶表达与患CWD的香鱼的累积死亡率密切相关。逆转录定量聚合酶链反应（RT-qPCR）和细菌攻毒实验表明，香鱼嗜冷黄杆菌分离株WA-1比香鱼分离株WA-2更活跃地表达fpcol基因且毒性更强。拥有假fpcol基因的樱鳟（Oncorhynchus masou）分离株WB-1对香鱼无害。迄今为止，经过充分研究的金属蛋白酶Fpp1和Fpp2被认为是毒力因子。然而，对香鱼毒性最强的分离株（WA-1）由于fpp基因中的缺失突变或转座子插入而没有Fpp活性。毒性较弱的WA-2分离株仅表现出Fpp1活性。综上所述，这些结果表明，在患CWD的香鱼中，胶原olytic活性而非Fpp活性与嗜冷黄杆菌分离株的毒力有关。
