Glucosyltransferase gene polymorphism among Streptococcus mutans strains

Genetic polymorphisms in genes coding for the glucosyltransferases were detected among Streptococcus mutans serotype c strains by Southern blot analysis with DNA probes located within the gtfB gene (H. Aoki, T. Shiroza, M. Hayakawa, S. Sato, and H. K. Kuramitsu, Infect. Immun. 53:587-594, 1986). Restriction endonucleases were used to examine genomic DNAs isolated from serotype a to h strains. The variations were readily detected among 33 strains of serotype c by EcoRI and PstI restriction enzyme digestions. Serotypes e and f, which are genetically similar to serotype c, also had comparable polymorphism; however, serotypes a, b, d, g, and h did not hybridize to the same DNA probes in parallel experiments. Further analysis of enzymatic activities for glucan synthesis and sucrose-dependent adherence revealed no significant differences among the serotype c strains. Our results suggested that genetic polymorphisms existing in S. mutans serotype c strains may reflect a complexity in genes coding for the glucosyltransferases, which are produced ubiquitously in members of the S. mutans group.