Streptococcus mutans is a major pathogen implicated in dental caries. Its virulence is enhanced by its ability to produce bacteriocins, called mutacins, which inhibit the growth of other Gram­positive bacteria. Sucrose­dependent adherence is mediated by glucans, polymers of glucose synthesized from sucrose by glucosyltransferase (Gtf) enzymes. S. mutans makes several proteins that have the property of binding glucans. We hypothesized that three of these glucan­binding proteins (Gbps), Gbps A, C and D, contribute to the carcinogenicity of S. mutans. The availability of suitable in vitro and in vivo systems and a thorough understanding of the genetics, biochemistry and physiology of the dental pathogen Streptococcus mutans have greatly advanced in understanding of important areas in the field of bacteriology such as interspecies biofilms, competence development and stress responses. S. mutans, as an organism had evolved in close association with the human host, as a novel Gram­positive model organism. The role of mutacins in vivo is unclear, however the antimicrobial activity of these substances may confer an ecological advantage for the producing strain in bacterial communities such as dental biofilm (56), and they may also be important for the establishment of S. mutans in vivo . Mutacins are peptide or protein antibiotics that are mainly bactericidal for other bacteria of the same or closely related species, as well as for other Gram­positive microorganisms, and are likely to confer an ecological advantage in diverse bacterial communities such as dental biofilm. The relationship between caries activity and the higher synthesis of some virulence factors by different genotypes of S. mutans has been related. . In this study, of 17 isolates, 10 isolates from caries­active and 7 isolates from caries­free were randomly selected for the molecular analysis for the mutacin I and II and for the (GTF) genes studies. It is concluded in the study that Mutacin I and II and (GTF) enzymes detected contribute to the carcinogenicity of S. mutans through a mechanism that may involve. alteration of biofilm architecture. In addition, reports of higher numbers of S. mutans genotypes with increased virulence in caries­active Subjects suggest the importance of microenvironmental factors in increasing the risk of caries active individuals.