A NOVEL AND EFFECTIVE CLOSTRIDIUM BIFERMENTANS CPSS2 AGAINST SELECTED FISH PATHOGENIC BACTERIA.

Several bacterial species induces a variety of fish diseases, resulting in a severe reduction of aquaculture output. However, the current fish disease control is mainly dependent on the environmental friendly chemical formulations. Thus, the present work aimed to isolate an effective antagonistic microorganism against common fish pathogenic bacteria. A total six isolates were isolated, among them one isolate showed antibacterial efficacy in in-vitro conditions. The isolated bacterium was identified as Clostridium bifermentans (GenBank accession No. KT367517). The inhibitory activity of C. bifermentans CPSS2 was evaluated at 25, 50 and 100 ?l (OD600= 1.0; 1 x 108cfu/ml) against pathogenic strain of FlavobacteriumcolumnareATCC 49513, Staphylococcus aureus JQ429749, AeromonashydrophilaJQ687063 and EdwardisellatardaJX280148 (2.6±0.5 x 109cfu/ml) in agar well diffusion method and was validated by a broth co-culture assay with their kinetics plots. Extracted intracellular protein of C. bifermentans CPSS2 exhibited significantly (p<0.05) high antagonistic effect against S. aureus JQ429749 followed by F. columnareATCC 49513and A. hydrophila JQ687063 and was least effective against E. tardaJX280148.The results of co-culture plate counts infer increasing count of C. bifermentans CPSS2 colonies positively antagonistic against the fish pathogenic bacteria. The result of phylogenetic study revealed that the isolated strain of C. bifermentans is closely related to C. bifermentans E079. The screening of inhibitory compounds from bacterium have clearly demonstrated that whole live bacteria and intracellular protein of C. bifermentans CPSS2 would be one of promising bio-control agent against common fish pathogen in freshwater aquaculture sector.