拮抗鲶爱德华氏菌的高地芽孢杆菌Yab4的鉴定及其应用前景研究

IDENTIFICATION AND APPLICATION PROSPECT OF BACILLUS ALTITUDINIS YAB4 ANTAGONIZING EDWARDSIELLA ICTALURI

  • 摘要: 为筛选拮抗鲶爱德华氏菌的肠道益生菌, 从鲶形目鱼类的肠道中分离耐热菌株, 通过体外抑菌实验以及宿主黏附实验, 筛选出一株既对鲶爱德华氏菌具有良好抑菌活性, 又能高效定植鲶爱德华氏菌易感宿主的菌株Yab4。通过16S rDNA与 gyrB构建系统发育树, Yab4菌株被鉴定为高地芽孢杆菌(Bacillus altitudinis)。该菌在pH 4.0—7.0及30—40℃耐受性较强, 同时对大部分水产常用抗生素敏感。将高地芽孢杆菌Yab4以喷雾的形式喷洒至饲料表面(5×109 CFU/kg), 经饲喂实验检测其对黄颡鱼的生长性能及免疫指标的影响。结果显示, 饲喂高地芽孢杆菌Yab4 28d的黄颡鱼生长性能高于对照组; 而且其血清中碱性磷酸酶、溶菌酶及总蛋白等先天免疫指标在28d时均显著上升, IL-1βTNF-αNF-κB p65等免疫相关基因表达水平呈显著性增高。通过腹腔注射鲶爱德华氏菌HSN-1的方式感染饲喂高地芽孢杆菌Yab4 28d的黄颡鱼, 发现高地芽孢杆菌Yab4饲喂组存活率达到60%, 较对照组提高了35%。以上结果表明, 研究筛选得到的拮抗鲶爱德华氏菌的高地芽孢杆菌Yab4具有良好的抗菌和益生效果, 并且有望作为一种饲料添加剂应用于鲶形目鱼类的替抗健康养殖。

     

    Abstract: Thermostable strains isolated from intestine of catfish were screened for their antagonism activity against Edwardsiella ictaluri, the causative agent of enteric septicemia of catfish (ESC) and red head disease. Four thermostable strains were selected, and their antagonistic activity against E. ictaluri was compared. Adhesion to zebrafish larvae was determined as CFU/larva after exposure for 30min. The isolate Yab4 was found to be highly adhesive and was identified as Bacillus altitudinis based on a phylogenetic tree constructed using 16S rDNA and gyrB sequences. After 28 days of feed supplementation with B. altitudinis Yab4, the growth performance of the treatment group is better than that of the control group, with a statistically significant difference observed between the two groups. Moreover, the innate immune indexes including alkaline phosphatase, lysozyme, and total proteins in serum increased significantly, and the expression levels of immune genes including IL-1β, TNF-α, and NF-κB p65 elevatedsignificantly as well. Most importantly, the survival rate of the yellow catfish fed with B. altitudinis Yab4supplementation reached 60%, marking a 35% increase compared to the control group when challenged with E. ictaluri HSN-1 infected intraperitoneally. This demonstrates that the potential of B. altitudinis Yab4 as a novel Bacillus probiotic to defend against E. ictaluri in catfish aquaculture through feed supplementation.

     

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