Fig. 4.

(A) An activity gel for glucosyltransferase activity. Glucosyltransferases associated with S. mutans were removed by incubation with SDS and then separated by SDS-PAGE. After washing away the SDS, the gels were incubated in the presence of sucrose, which resulted in the in situ synthesis of glucan, appearing as a white precipitate within the gel. (B) Transcription of the gtfB and gtfC genes was measured in the parental and mutant strains via quantitative real-time PCR. The probes did not discriminate between gtfB and gtfC, so the values represent the cumulative expression of these two contiguous genes. The expression in the damA mutant strain was significantly higher than that in each of the other strains by a Student t test (P < 0.001).