兔源抗动物腹泻益生菌Tu-1的分离、鉴定及耐受性研究

本研究旨在从健康兔肠道内分离出一株对大肠杆菌有拮抗活性的菌株，并对其鉴定到属。选用平板抑菌圈法，从兔子盲肠中分离得到64株对大肠杆菌有拮抗作用的细菌，对其中14株拮抗作用较强的菌株进行了复筛，其中抑菌圈直径大于20mm的4株，抑菌圈直径在15mm~20mm的8株，另外2株拮抗作用较小，其中Tu-1对大肠杆菌的拮抗作用最强，抑菌圈直径达到21.4mm。在耐受性实验中，Tu-1对酸性环境、胆酸盐和高渗透压均表现出耐受性。对其形态及生理生化特征进行了研究分析，发现与芽孢杆菌相似，将所测得的16S rDNA序列用BLAST软件在GenBank数据库中进行比对，选取序列相似性高的菌株，用Clustal X(1.8)软件进行16S rDNA相似性分析，Neighbor-Joining法构建系统发育树。Tu-1与Bacillus velezensis的相似性水平均达到99.77%，鉴定该菌为Bacillus velezensis。

Isolation , Identification and Tolerability of Rabbit Intestinal Probiotics Strains Tu-1

This experiment was conducted to isolate a strain of bacteria with antagonism to E.coli from Rabbit caecum.,and Identified to genus. By screening on plate, 64 strains of bacteria with antagonism to E.coli were isolated from Rabbit caecum. After secondary screening, in the 14 strains of stronger antagonism, 4 strains of bacteria’ diameter of inhibition zone are more than 20mm, 8 strains of bacteria’ diameter of inhibition zone are among 15mm-20mm, 2 strains of bacteria’ antagonism are weaker, strains Tu-1 has the strongest antagonism, the diameter of inhibition zone reached 21.4mm. In the tolerance test, strains Tu-1 tolerated acid environment, bile salts and high osmotic pressure. Morphology, physiological and biochemical characteristics of strains Tu-1 were studied, as a result its characters were very similar with Bacillus, A phylogenetic tree was constructed by comparing with the validly published 16S rDNA sequences of the related strains from GenBank using the Neighbor-Joining method of Saitou and Nei and the Clustal X program to do the multiple alignments. The 16S rDNA sequence of strains Tu-1 shared 99.77% similarity probability with Bacillus velezensis. StrainTu-1 was identified as Bacillus velezensis.