Isolation, Characterization and Molecular Identification of Potential Probiotic Bacterium, Bacillus amyloliquefaciens CS4 from gut of Snakehead Fish, Channa striata (Bloch, 1793)

Nobel surya pandi durai R.; Perumal P.

Abstract

The present study was to isolate and characterize the potential probiotic bacterium from the gutof healthy fish, Channa striata. Totally, 37 bacteria were isolated from the gut region, in whichonly 25 isolates that showed catalase negative were selected. Among the selected isolates, CS4exhibited maximum inhibitory activity against fish (Aeromonas hydrophila, Vibrio harveyi,Vibrio parahaemolyticus) and human (Serratia marcescens) pathogenic bacteria. Theisolate CS4 exhibited potential tolerance to 0.5% bile salts at 24 h and was also capable togrow up to 2% bile concentration. The pH tolerance assay showed that the growth rate of CS4changed significantly (p< 0.0001) from pH 3 to 7. The CS4 exhibited highest hydrophobicadhesion (65.66%) with xylene and displayed autoaggregation of 71.4 %. The isolate (CS4) didnot have any haemolytic activity against human blood. The antibiotic susceptibility of CS4 wasfound that sensitive to gentamycin, chloramphenicol, cephalosporin, amoxicillin, vancomycinand resistant to methicillin, penicillin and ampicillin. The molecular identification of 16S rRNAgene sequencing of CS4 showed high similarity (99%) with Bacillus amyloliquefaciens.Therefore, the effective strain CS4 isolated from the gut region of Channa striata was confirmedas Bacillus amyloliquefaciens and which could be a preferable choice as a probiotic inaquaculture.Keywords: Probiotic, Bacillus amyloliquefaciens, Channa striata, Fish gut bacteria