Isolation and characterization of a virulence related Vibrio alginolyticus strain Wz11 pathogenic to cuttlefish, Sepia pharaonis

摘要

Vibrio alginolyticus is a ubiquitous marine opportunistic pathogen that can infect various hosts in marine environment. In the present study, V. alginolyticus strain Wz11 was isolated from diseased cuttlefish, Sepia pharaonis, with 20% of promoted death and high survival capacity in skin mucus and tissue liquid. Its growth, siderophore production, and expressions of haemolysin and swarming related genes were characterized under iron limited conditions. The minimal inhibitory concentration (MIC) of 2,2'-dipyridyl (DP) to V. alginolyticus strain Wz11 was 640 mu M. While growth of V. alginolyticus strain Wz11 was inhibited by DP, production of ironseizing substances, haemolytic activity and swarming motility were increased. Moreover, expressions of haemolysin related genes tilt, tdh and vah and flagellar related genes figH, fliC, fliD and fliS were also characterized using real-time reverse transcriptase PCR. Expression of tdh was up-regulated to 7.7-fold, while expressions of till and wilt were down-regulated to 0.016-fold and 0.03-fold, respectively. The expression of fliC, flgH, fliD and fliS was up-regulated to 4.9-, 3.8-, 8.6- and 4.5-fold, respectively. Concluded from our results suggested that V. alginolyticus strain Wz11 was considered as a potential pathogen of S. pharaonis, and iron level played an important role in the production of iron-seizing substances, and activities of haemolysin and bacterial swarming as well as their related gene expressions.