育肥饲料中虾青素含量对雄性中华绒螯蟹肠道和鳃部可培养优势细菌数量和组成的影响

在育肥饲料中添加虾青素会影响中华绒螫蟹肠道及鳃内的可培养优势菌群以及机体的免疫力,本实验旨在探讨饲料中虾青素含量及养殖水体对其肠道和鳃部菌群的影响。采用不同虾青素含量的饲料(0.00、26.60、41.62、81.37和75.35 mg/kg,分别对应饲料1#~5#)对雄性中华绒螫蟹进行育肥70 d后,利用基础培养基和选择性培养基对其肠道、鳃及养殖水体中的细菌进行传统分离和纯化,所得菌株进行16S rRNA测序,再进行同源性分析后做系统进化树。结果发现,在分离获得的106株细菌(登录号:KU570293~KU570368,KU570370,KU570372~KU570383,KU601302~KU6013 16,KU720553)中,92株为优势菌株,其中,肠道、鳃部和水体各29、32和31株。肠道中的可培养优势细菌属于柠檬酸杆菌属、假单胞菌属和气单胞菌属;而鳃中可培养优势细菌属于柠檬酸杆菌属、芽孢杆菌属、假单胞菌属和气单胞菌属;养殖水体中可培养优势细菌属于芽孢杆菌属、气单胞菌属、柠檬酸杆菌属、假单胞菌属和黄杆菌属。饲料2#组肠道中可培养细菌总数最高(1.06×10~8cfu/g);饲料5#肠道中的潜在致病菌数量最低,但其可培养细菌总数显著高于其他饲料组;饲料3#组肠道和鳃中潜在致病菌数量相对较高。研究表明,饲料中添加不同含量的虾青素能够显著影响雄性中华绒螫蟹肠道和鳃中的菌群构成,但对水体中可培养细菌数量无显著影响。本研究首次对投喂不同含量虾青素饲料的育肥期雄性中华绒螫蟹肠道、鳃及养殖水体可培养的优势细菌数量和组成进行分析,探究了饲料中虾青素含量以及养殖水体与蟹肠道内可培养细菌之间的联系,为中华绒螫蟹营养免疫和菌群调控提供了理论基础。

Effect of dietary astaxanthin on culture-based dominant bacterial community isolated from the intestinal tract and gills of male Chinese mitten crab (Eriocheir sinensis)

Chinese mitten crab (Eriocheir sinensis) is one of the important economic species of freshwater aquaculture in China. Dietary astaxanthin affects the number and composition of culture-based dominant bacteria from intestinal tract and gills, which is closely linked to the body''s immunity. In order to realize the relationship between dietary astaxanthin and the balance of bacteria in intestinal tract and gills, five diets with various concentration astaxanthin (0.00, 26.60, 41.62, 81.37 and 75.35 mg/kg, respectively) were fed to adult male crabs for 70 days. The dominant bacteria number and composition of five crab groups were measured by culture-based enumeration techniques, and then the isolates were sequenced by 16S rRNA gene analysis. A total of 106 bacterial strains were isolated from the intestinal tract, gills and aquaculture water. 92 bacterial strains were dominant bacteria, of which 29 bacterial strains were from intestinal tract, 32 bacterial strains from gills and 31 bacterial strains from aquaculture water. At the genus level, the dominant bacteria were Citrobacter, Pseudomonas and Aeromonas in the intestinal tract, by contrast, the dominant bacteria were Citrobacter, Bacillus, Pseudomonas and Aeromonas in the gill, and the dominant bacteria were Bacillus, Aeromonas, Citrobacter, Pseudomonas and Chryseobacterium in the aquaculture water. The total number of culture-based dominant bacteria in intestinal tract was the highest (1.06×10⁸ cfu/g) in group 2. The number of potential pathogenic bacteria of group 5 (75.35 mg/kg) was significantly decreased in intestinal tract. However, the total number of dominant bacteria of group 5 was significantly higher than the other four groups in the gill, and the numbers of dominant bacteria had no significant difference in all five groups in aquaculture water. To conclude, dietary astaxanthin with various concentrations could significantly affect the culture-based dominant bacteria composition of intestinal tract and gill in male E. sinensis. The number of potentially pathogenic bacteria in intestinal tract and gills accounted for high proportion in group 3. This study for the first time analyzed the effect of astaxanthin on number and composition of culture-based dominant bacteria of intestinal tract and gills in male Chinese mitten crab, and discussed the relationship between concentration of dietary astaxanthin, aquaculture water and the number of culture-based dominant bacteria from intestinal tract and gill, and the results may provides a theoretical basis for E. sinensis diet exploitation and bacterial flora control in the future.