Thus, the Gtf enzymes of S. mutans and the adhesive glucans likely
contribute to the enhanced biofilm formation by L. casei, and probably S. oralis, when grown in mixed-species biofilms with S. mutans. Notably, enhanced biofilm formation by Lactobacillus plantarum and Lactobacillus rhamnosus was noted in a mucin-based medium , so the presence of polysaccharides may have a general ability to promote biofilm formation by lactobacilli. However, the actual mechanism for the enhancement of L. casei levels in biofilms with S. mutans requires further investigation. While the close association of L. casei and S. mutans in carious sites is well documented, little information is available concerning the interaction between these two bacteria with respect to S. mutans biofilm formation and its cariogenicity. Selleck Omipalisib While co-cultivation with S. mutans significantly enhanced biofilm formation by L. casei, the sessile population SP600125 price of S. mutans was also found to be increased by more than 2-fold in dual species model with L. casei (Figure 2), which is contrary to what was observed with the other bacteria studied. While the exact nature and the underlying mechanism await further investigation, the interaction observed between S. mutans and L. casei may partly explain the prevalence and the close association of these two bacteria in cariogenic plaque. Expression of genes critical to cariogenicity of S. mutans can be altered when grown in mixed-species
biofilms RealTime-PCR was used to analyze the expression of several genes that have critical roles in bacterial adherence and biofilm accumulation by S. mutans [7–10], including spaP, gtfB and gbpB. As shown in Figure 3,
slight decreases were observed in expression of spaP, gtfB and gbpB by S. mutans when grown in dual-species with S. sanguinis as compared to those in mono-species biofilms, although the differences were not statistically significant. When grown in dual-species with L. casei, however, expression of spaP, gbpB and gtfB by S. mutans was decreased by as much as 40-fold, at a significance level of P < 0.05 for spaP and P < 0.001 for gtfB and gbpB, respectively, as compared to cells in mono-species biofilms. The expression of spaP (P < 0.05) and gbpB (P < 0.001), but not gtfB, was also lower by more than 30-fold in S. mutans when grown with S. oralis. As compared to mono-species Y-27632 2HCl biofilms, expression of luxS was decreased by more than 7-fold in cells grown with L. casei (P < 0.001) and by more than 15-fold in cells with S. oralis (P < 0.001), but again no significant differences were observed when S. mutans was grown with S. sanguinis. Expression of brpA was decreased by more than 3-fold (P < 0.05) in cells grown with S. oralis, but no major differences were observed when grown with S. sanguinis and L. casei. As a control, the expression of the ldh gene, a constitutively expressed gene (Wen and Burne, unpublished data) , was also analyzed and no significant differences were observed between S.