Isolation and growth conditions of Bdellovibrios in coastal areas of Shanghai

ObjectiveThe present experiment investigated the distribution of Bdellovibrio in coastal areas of Shanghai, studied its biological properties, in order to provide reference for application of Bdellovibrio in prevention and treatment of aquatic animal diseases. MethodThe researchers isolated Bdellovibrios from coastal areas of Shanghai using double lay-er agar plate, and used 16S rRNA gene sequence analysis to identify the bacteria. Lysis spectrum, saltinity tolerance, lysis diofference and culture mode of Bdellovibrio were studied. ResultTwelve strains of Bdellovibrio were isolated from the coastal areas of Shanghai. Among them, three strains(No. 4.2, 5.1 and 3N.3) had strong lysis effects to Vibrio, but had no lysis effects toward beneficial bacteria including Bacillus subtilis, B. licheniformis, B. natto, Paracoccus denitrificans, Streptococcus lactis and Lactobacillus bulgaricus. Three strains of Bdellovibrio had good growth condition in the range of 1.5%-3.0% salinity. Lysis effects of strain 5.1 toward Vibrio alginolytic were more significant than V. parahaemolyticus and V. harveyi,and the difference reached significant level(P<0.05). Inactivation of host bacteria could effectively increase growth rate and concentration of the bacteria, and reached the peak after 60 h. After asynchronous fermentation of Bdellovibrio and host bacteria(Escherichia coli) Bdellovibrios amount reached the peak after 72 h of culture. ConclusionBdellovibrios from coastal areas of Shanghai has great phagocytic ability, which can infect and crack the main seawater pathogenic bacteria and freshwater pathogenic bacteria but cannot kill beneficial bacteria. It is euryhaline. Therefore, Bdellovibrios can be used in development of microbial agents.