从山东荣成养鱼场发病牙鲆分离到一株病原菌M3 ,革兰氏阴性 ,杆状 ,能运动 ,菌落半透明 ,用BIOLOG细菌鉴定系统不能鉴定。通过 1 6SrDNA序列分析和同源性检索发现M3菌株与弧菌属的同源性较高 ,为 94%～ 98%。系统发育学分析表明菌株M3与鳗弧菌关系最近 ,相似性为 99 6 % ,其生化性状也和鳗弧菌的特征相似 ,故可把M3定为鳗弧菌 (Vibrioan guillarum)。 Pathogenic bacteria M3 were isolated from the flounder in Shandong Rongcheng fish farm. Gram-negative, rod-shaped, motile, colonies were translucent and could not be identified by BIOLOG bacterial identification system. The results of 16S rDNA sequence analysis and homology search showed that the homology of M3 strain to Vibrio was 94% -98%. Phylogenetic analysis showed that strain M3 had the closest relationship with Vibrio anguillarum, with a similarity of 99.6%. Its biochemical trait was also similar to Vibrio anguillarum, so M3 could be designated as Vibrio guanum.