RESUMEN
Dental caries is an important global health concern and Streptococcus mutans has been established as a major cariogenic bacterial species. Reports indicate that a rare sugar, Dtagatose, is not easily catabolized by pathogenic bacteria. In the present study, the inhibitory effects of Dtagatose on the growth and biofilm formation of S. mutans GS5 were examined. Monitoring S. mutans growth over a 24 h period revealed that Dtagatose prolonged the lag phase without interfering with the final cell yield. This growth retardation was also observed in the presence of 1% sucrose, although it was abolished by the addition of Dfructose. S. mutans biofilm formation was significantly inhibited by growth in sucrose media supplemented with 1 and 4% Dtagatose compared with that in a culture containing sucrose alone, while S. mutans formed granular biofilms in the presence of this rare sugar. The inhibitory effect of Dtagatose on S. mutans biofilm formation was significantly more evident than that of xylitol. Growth in sucrose media supplemented with Dtagatose significantly decreased the expression of glucosyltransferase, exoßfructosidase and Dfructosespecific phosphotransferase genes but not the expression of fructosyltransferase compared with the culture containing sucrose only. The activity of cellassociated glucosyltransferase in S. mutans was inhibited by 4% Dtagatose. These results indicate that Dtagatose reduces waterinsoluble glucan production from sucrose by inhibiting glucosyltransferase activities, which limits access to the free Dfructose released during this process and retards the growth of S. mutans. Therefore, foods and oral care products containing Dtagatose are anticipated to reduce the risk of caries by inhibiting S. mutans biofilm formation.
Asunto(s)
Biopelículas/efectos de los fármacos , Hexosas/farmacología , Streptococcus mutans/efectos de los fármacos , Streptococcus mutans/crecimiento & desarrollo , Metabolismo de los Hidratos de Carbono/efectos de los fármacos , Metabolismo de los Hidratos de Carbono/genética , Regulación Bacteriana de la Expresión Génica/efectos de los fármacos , Regulación Enzimológica de la Expresión Génica , Hexosas/metabolismo , Streptococcus mutans/genética , Streptococcus mutans/metabolismoRESUMEN
Bacteroides fragilis is a member of the normal intestinal flora and is involved in host immunostimulation via TLR2. On the bacterial cell surface, glycoconjugates, such as LPS and capsular polysaccharide A (PSA), have been reported to participate in host immunostimulation via TLR2. Previously, we identified a TLR2-stimulating lipoprotein in B. fragilis cells. In this study, we demonstrated that TLR2-stimulating principal molecules in glycoconjugate fractions prepared from B. fragilis are contaminating proteinous molecules, which may also be lipoproteins. The glycoconjugate fractions were prepared by phenol-hot water extraction of B. fragilis wild type and PSA-deficient strains, followed by hydrophobic interaction chromatography. TLR2-stimilating activities of the fractions were not affected by PSA deficiency. By in-gel TLR2-stimulation assay, molecules in high-molecular-mass area, where capsular polysaccharides were migrated, were found not to stimulate TLR2, but those in the range of 15-40 kDa were active. Further, proteinase K could digest the latter molecules and the TLR2-stimulating activities were migrated to the area of below 15 kDa. These results support that proteinous molecules, which are estimated to be lipoproteins, are responsible for almost all TLR2-stimulating activity in the glycoconjugate fractions prepared from B. fragilis.