河流弧菌在天然海水与人工海水中的饥饿效应

Effects of starvation induced in natural seawater and artificial seawater on the pathogenic Vibrio fluvialis

对数生长期河流弧菌分别悬浮于天然海水和人工海水后于28℃进行饥饿试验。在饥饿初期,两种海水中河流弧菌的总菌数、活菌数、菌落形成单位数都明显上升,但天然海水中的河流弧菌生长时间持续更久、增长幅度也更大;饥饿中、后期,总菌数都保持稳定,而可培养菌数与活菌数逐渐下降,其中可培养菌数下降幅度高于活菌数,人工海水中的河流弧菌下降幅度高于天然海水。河流弧菌对青石斑鱼表皮粘液的粘附量随着饥饿时间延长先上升后下降。与对数生长期相比,饥饿60d的可培养细胞对热和紫外线的耐受性提高。饥饿细胞的间接ELISA最低检测限高于对数生长期细胞。通过SDS-PAGE分析菌体蛋白发现饥饿细胞的蛋白质条带减少。腹腔注射饥饿60d的河流弧菌不会引起小鼠死亡,而对数生长期细胞能够引起小鼠死亡。研究结果表明,河流弧菌能够在温暖的人工海水和天然海水中长时间饥饿存活,但是饥饿细胞的毒力较低。

Marine bacteria are in a stable starvation condition in seawater for most of the time. Expounding the survival strategy of pathogen in marine ecosystems is helpful understanding the characteristic of epidemiology. To get a better understanding of the starvation survival strategy of pathogenic V. fluvialis isolated from diseased Epinephelu~ awoara, bacterial cells in log-phase were suspended in natural seawater and artificial seawater and kept at 28 ℃ for starvation study. At the initial starvation stage, all of the total bacteria number, viable bacteria number and CFU number of V. fluvialis in both seawater increased remarkably, but V. fltwialis in natural seawater exhibited more increase during a longer period than the counterpart in artificial seawater. After reaching their peaks, total bacteria number of V. fluvialis rem,amed stable, while the CFU number and viable bacteria in artificial seawater fell more quickly than those in natural seawater. Starvation of V. fluwialis both in natural and artificial seawater resulted in increase of bacterial adhesion to the E. awoara＇ s skin mucus at the initial stage and sharp decrease at the later stage. Starved cells showed better resistance to high temperature and UV. The lowest detection limit of starved cells detected by indirect ELISA was higher than that of log phase cells. The result of SDS-PAGE showed less cellular protein bands of starved cells than the unstarved ones. The starved V. fltwialis were less virulent to mice than the log phase bacteria. The results indicated that V. fltwialis could survive for a long time in both natural and artificial seawater, and the starved cells were less virulent and more resistant to enviromental stresses.