研究了石斑鱼肠道原籍嗜冷杆菌SE6在体外的抑菌特性及对人工胃肠液的耐受特性,在此基础上研究了饲料中添加SE6( 108 CFU/g)对斜带石斑鱼生长性能和免疫功能的影响.体外试验结果表明:SE6对副溶血弧菌、哈维氏弧菌、梅氏弧菌和金黄色葡萄球菌等常见水产致病菌均有一定的抑制作用.pH为4.0的人工胃液能促进SE6的生长,处理2和4h存活率分别为110.7％和173.0％；pH为3.0的人工胃液处理2h后活菌数为1.59×105 CFU/cm3,存活率为1.36％,但SE6不能耐受pH为2.0的人工胃液.经浓度分别为0.1％,0.3％,0.5％和0.7％的胆盐处理3h后,SE6的存活率分别为89.17％,88.33％,77.17％和12.33％.动物试验结果显示:投喂SE660 d后试验组饵料系数(0.95±0.01)显著低于对照组(1.03±0.02).试验组血清补体C3在试验全期均高于对照组,补体C4含量在投喂SE6 60 d时显著上升.血清IgM含量在投喂30 d时显著上升.总之,嗜冷杆菌SE6能抑制多种常见病原菌的生长,而且对模拟胃肠道环境具有一定的耐受能力,添加到饲料中能显著提高石斑鱼饵料利用率,增强动物的免疫功能.%The antibacterial activity and tolerance to mimic gastrointestinal environments of the probiotic Psychrobacter sp. SE6 isolated from the gut of grouper(Epinephelus coioides) were evaluated in vitro. On the base of the in vitro results, a 60 d feeding trial was conducted to assess the effect of dietary administra-tion(108 CFU/g) of SE6 on the growth, feed utilization and immune responses of E. Coioides. In vitro results show that SE6 exhibits antagonistic activity against pathogenic Vibrio parahaemolyticus, V. Harveyi, V. Metschnikovi and Staphyloccocus aureus. After 2 and 4 h of incubation with artificial gastric juice at pH 4. 0, the survival ratio of SE6 is 110. 7% and 173% , respectively. After treated with artificial gastric juice at pH 3. 0 for 2 h, the survival ratio and the survival count are 1. 36% and 1. 59×105CFU/cm3 , respectively. However, SE6 cannot survive in artificial gastric juice at pH 2. 0. Psychrobacter sp. SE6 exhibits good tolerance to artificial intestinal juice (different concentrations of bile salt and trypsin) , the survival ratios of SE6 are 89. 17%, 88. 33%, 77. 17% and 12. 33% respectively after incubated in artificial intestinal juice with 0. 1 % , 0. 3% , 0. 5% and 0. 7% bile salt for 3 h. In vivo results show that Psychrobacter sp. SE6 significantly decreases the feed conversion ratio (FCR) of E. Coioides. Serum lysozyme activity shows no significant differences between the probiotic group and the control group during the whole experiment period, while an increasing trend of total superoxide dismutase (T-SOD) activity in the probiotic group is observed. Serum complement component 3 (C3) level of the probiotic group is higher than that of the control in the whole feeding period, while complement component 4 (C4) level of the probiotic group is significantly higher than that of the control at Day 60. The IgM level of probiotic group is significantly higher than that of control group at Day 30, but no significant difference is observed at Day 60. In conclusion, Psychrobacter sp. SE6 shows good antagonistic activities against potential pathogens and tolerance to mimic gastrointestinal environment, and the dietary administration of Psychrobacter sp. SE6 improves the feed utilization and immune responses of E. Coioides.
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