Abstract:

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.