Characterization of Bacillus sp. PU-T8 Isolated from Tiger Puffer Fish Takifugu rubripes as Probiotics

Bacillus sp., PU-T8 strain, isolated from tiger puffer fish Takijugu rubripes showed growth-inhibitory activity against bacterial fish pathogens such as Edwardsiella tarda and Vibrio anguillarum. Physiological characterization and the phylogenetic analysis based on 16SrDNA sequences indicated that the strain PU-T8 is most closely related to Bacillus subtilis strains. The strain was considerably stable in acidic buffers (pH 2.0-4.0) and in buffers with digestive enzymes such as pepsin (pH 2.0) and pancreatin (pH 8.0). Cells suspended in PBS also remainded viable at 103 cfu/ml after heat treatment at 100ｰC for 60 min. The strain PU-T8 grew well in Z-AII broth media with 0.1 M to 2.0 M NaCl. Crude extract obtained with ethyl acetate from the culture supernatant of the strain PU-T8 showed growth-inhibitory activity against fish pathogens on the double-layer agar plates