Abstract: Bacillus subtilis is a kind of aerobic, spore-producing, non-pathogenic, non-capsular and motile Gram-positive bacilli. Due to its excellent probiotic characteristics, it is often added to feed as probiotics. Samples were collected from pigs of pig farms around Tianjin. After a process of isolation, the experimental bacteria numbered as Y33245 was studied by morphology, physiological and biochemical characteristics and identified by 16S rDNA sequence analysis. Also further experiments studied its characteristics by doing drug sensitive test, salt and cholate resistance test, artificial gastric and intestinal fluid（put the strain into the fluid）test. The final experimental results showed that this was a Bacillus subtilis strain which was highly sensitive to a variety of antimicrobial agents. Its survival rate in artificial gastric and intestinal fluid reached up to 61.3% and 72.6% respectively, which showed its strongly resistant characteristic. Meanwhile its biological characteristic has been studied. All these could provide reference data for the follow-up study on microecological agents.

Key words: Bacillus subtilis, 16S rDNA, characteristics, isolation and identification