Sucrose-dependent adherence of Streptococcus mutans to smooth surface and chemical structure of extracellular glucans related to adherence (author's transl)

Abstract

Sucrose-dependent adherence of Streptococcus mutans strains to a smooth glass surface was studied. After cultivating the microorganism in sucrose-containing broth medium, cells and glucans yielded in the culture were fractionated into firm adherent (ad-1), loose adherent (ad-2) and nonadherent (non-ad) fractions based on their adhesiveness to the surface of culture tube. The amounts of cells and glucans in each fraction were determined to elucidate the relationship between cell adherence and glucan synthesis. The results suggested that the amount of ad-1 cells strongly correlated to that of ad-1 insoluble glucan (IG) and also to the total amount of IG produced in the culture. On the other hand, extracellular glucans produced by S. mutans cultured on sucrose could be separated into IG-1, IG-2 and soluble glucan (SG) based on their solubility in water. The adherence ability of the Streptococcus distinctly depended on their productivity of IG, especially IG-1.Chemical structure of these glucans was investigated by infrared spectrophotometry, acid hydrolysis, acetolysis, periodate oxidation, and methylation analysis. The average proportions of α-1, 6-glucosidic linkages were 38% for IG-1, 49% for IG-2 and 56% for SG, while those of α-1, 3-glucosidic linkages were 57% for IG-1, 46% for IG-2 and 37% for SG. The IG-1 produced by S. mutans JC 2 contained 9% α-1, 3, 6-linked branching residues, 9% non-reducing terminal residues, 36% α-1, 6-linked units and 46% α-1, 3-linked units. The SG of the strain contained 10% α-1, 3, 6-linked branches, 10% terminals, 47% α-1, 6-linked units and 33% α-1, 3-linked units. The alkali-solubility of the glucans produced by S. mutans appeared to be ascribed to their contents of α-1, 3-and α-1, 6-glucosidic linkages.