Regulation of expression of Streptococcus mutans genes important to virulence

Studies were initiated to investigate the regulation of Streptococcus mutans genes which are believed to be important to virulence. Operon fusions were constructed between S. mutans gene regulatory regions and a promoterless chloramphenicol acetyltransferase gene (cat) found on the plasmid pMH109. Specifically, fusions were generated between cat and the S. mutans genes encoding fructosyltransferase (ftf) and the glucosyltransferase B/C (gtfB/C) operon. Constructs were confirmed by restriction enzyme analysis, and the fusions were subcloned into the integration vehicle pVA891. Following generation of multimeric DNA, recombinant plasmids were introduced into the s. mutans genome by Campbell-type insertion, resulting in single-copy operon fusions. Chloramphenicol acetyltransferase specific activities were used to monitor the expression of the S. mutans gtfB/C operon and ftf determinants. The expression of these genes is increased by the presence of sucrose and is followed by a rapid decline in expression over time. Additionally, expression of the gtfB/C operon is increased in S. mutans cells bound to artificial tooth pellicles.