Utilization of a mini-mu transposon to construct defined mutants in Streptococcus mutans

The gtfB gene coding for glucosyltransferase-I (GTF-I) activity previously isolated from Streptococcus mutans GS-5 was insertionally inactivated with the newly constructed transposon MudE in an Escherichia coli background. Insertion of MudE into various regions of the gtfB gene led to inactivation of GTF-I activity. The altered gene was introduced back into S. mutans GS-5 by transformation and produced mutants defective in insoluble glucan synthesis as well as the ability to colonize smooth surfaces in the presence of sucrose. Therefore, the MudE transposon can be utilized to produce specific mutants in oral streptococci as well as in other transformable Gram-positive bacteria expressing an erythromycin-resistance marker.