弧菌拮抗菌的筛选及其对凡纳滨对虾的抑菌防病作用

从海洋沉积物中分离到2株弧菌拮抗菌(H2和H4),经生理生化特性、16S rRNA基因序列分析分别鉴定为短小芽孢杆菌(Bacillus pumilus H2)和地衣芽孢杆菌(Bacillus licheniformis H4). H2和H4菌株均对需钠弧菌的生长有显著的抑制作用;但只有H2菌株在模拟养殖动物小肠环境中生长良好. 选择H2进行模拟试验(20尾凡纳滨对虾虾苗为1组).结果表明,对照组(不接种)虾苗存活32h,接种弧菌的试验组虾苗仅存活16h,同时接种H2菌株和弧菌的试验组虾苗存活48h,而仅接种H2菌株的试验组虾苗存活了72h,说明菌株H2可显著提高凡纳滨对虾的存活时间.现场试验中,100L养殖池中(50尾虾/池),分别接种0 (对照), 103, 104 CFU/mL的H2菌株并养殖14d,再用104 CFU/mL需钠弧菌处理14d.接种104 CFU/mL H2菌株的试验组,虾的死亡率仅为12.5%,显著低于对照组的30.8%(P0.05).

Screening of probiotic strains and their protection against vibriosis in juvenile shrimp(Litopenaeus vannamei)

Two bacterial strains, H2 and H4, were isolated from marine sediment and identified as Bacillus pumilus H2 and Bacillus licheniformis H4, respectively, based on their physiological properties and the analysis of 16S rRNA gene sequence. Both strains showed significantly inhibitory effects against the growth of Vibrio natriegens by antimicrobial activity assay. However, only strain H2 could survive in the intestinal conditions as revealed by the simulated gastro intestinal tract (GIT) test, keeping cell number stably at 1010 CFU/mL. B. pumilus H2 was also benefit to the survival of juvenile shrimp (Litopenaeus vannamei) as revealed by the flask bottle test (20 shrimp fries for every bottle as a group). Probiotic effect of B. pumilus H2 to juvenile shrimp was carried out in aquaculture tanks with 100L each with 50 shrimps. Juvenile shrimp were exposed to B. pumilus H2 at 0 (as control), 103 and 104 CFU/mL for 14d before a challenge with Vibrio natriegens at 104 CFU/mL for 1 d infection. The final mortality of the shrimp group treated with 104 CFU/mL B. pumilus H2 was only 12.5%, much lower than the group treated with 103 CFU/mL B. pumilus H2 (28.3%) and the control group (30.8%, P<0.05); and the average weight and length of the shrimp group treated with 104 CFU/mL B. pumilus H2 were also a bit higher than those of the control group.