FIG 1.

The stimulatory effect of raffinose on biofilm formation by S. mutans. (A) Structural comparison of sugars used in this study. (B) Biofilm formation assay in TSB or SDM supplemented with 0.25% (wt/vol) sucrose, glucose, or raffinose. We used sucrose and glucose as biofilm-inducible and non-biofilm-inducible controls, respectively. (C) The impact of a low concentration of sucrose and the stimulatory effect of raffinose on biofilm formation. To evaluate the effects of a low concentration of sucrose, we used SDM with 0.002% sucrose, which is not sufficient to induce a biofilm, as a base medium. We tested whether raffinose has a stimulatory effect of biofilm by adding various concentrations of raffinose to cell culture. Glucose was used as a negative control. (D) Comparison of the biomass of a biofilm formed by WT and ΔagaL mutant strains. Biofilm biomasses were comparable in the WT and ΔagaL mutant strains. The data indicate means ± standard deviations (SD) of the results from three independent experiments. The asterisks indicate a significant difference between two groups (Student's t test; P < 0.05).