Bacillus subtilis as potential probiotic for aquaculture industry

The present study evaluated the in-vivo and in-vitro potential of Bacillus subtilis to showcase probiotic function, in terms of extracellular inhibitory substance and enhancement of artemia larvae (model organism) when challenged with pathogenic Vibrio harveyi. Cell free extracts of Bacillus subtilis did not show any inhibitory activity against growth of V.harveyi on agar antagonism assay, hence it does not release extracellular inhibitory substance. But, the survival of artemia larvae was enhanced up to 20% with the treatment of B. subtilis when challenged with V. harveyi, compared with the experiment which did not receive any B. subtilis treatment, where 100% mortality was seen. Protection of B. subtilis over V. harveyi challenge could be seen the best when the B. subtilis treatment was given prior to V.harveyi challenge and could not be seen at all when B. subtilis treated after V.harveyi challenge. Better protection effect could also be seen when the concentration B. subtilis treatment is higher than that of V.harveyi challenge. The study reports that treatment of Bacillus subtilis to artemia larvae could enhance its survival rate if attacked by pathogenic Vibrio harveyi, hence Bacillus subtilis has the potential probiotic property. Results indicated that the probiotic activity of Bacillus subtilis is not limited to production of inhibitory substance only. Eventhough there are no inhibitory substance produced, there are potential for Bacillus subtilis to show probiotic property in-vivo.