10.22376/ijpbs.2019.10.1.p1-12 Volume 8 Issue 1 2017 (January - March) As part of a screening program aimed at the discovery of new lead compounds for the treatment of oral diseases, probiotic lessThan i greaterThan Bacillus megaterium lessThan /i greaterThan isolated from fish gut was studied for its anticaries activity.Our objective is to enumerate the antibacterial effect of lessThan i greaterThan Bacillus megaterium lessThan /i greaterThan against the dental caries causing micro organism lessThan i greaterThan Streptococcus mutans. lessThan /i greaterThan Agar well diffusion to determine Zone of inhibition and MIC value was assessed through broth 2-fold macro dilution method.Our study result showed that the fish gut bacteria possess potent inhibitory activity against potentially deleterious oral bacterial pathogen, lessThan i greaterThan Streptococcus mutans lessThan /i greaterThan (P C. SUMATHI, A. NANDHINI, JAYANTHA PADMANABAN Bacillus megaterium, Probiotic, Dental Caries, Streptococcus mutans, oral pathogen 270-274