口腔Ｓｔｒｅｐｔｏｃｏｃｃｕｓ ｓａｌｉｖａｒｉｕｓの菌体外多糖の合成と付着に及ぼすグルカナーゼの影響

Abstract

Synthesis of glucans and fructans from sucrose and adherence to glass by extracellular enzymes of two strains of oral Streptococcus salivarius were compared.The enzyme of strain Y5 produced a large amount of sticky deposits on a glass surface whereas the nzyme of strain S2 formed a much smaller amount of fragile deposits. Products of the S2 enzyme consisted of nearly equal amounts of water-insoluble and water-soluble glucans and fructans (IG, SG, IF, SF). Major products of the Y5 enzyme were IG with a trace of SG and IF. Methylation analysis together with glucanase susceptibility tests revealed that IGs and SGs of both strains consisted of an α-1, 3-linked linear chain as a backbone sequence possessing α-1, 6- and α-1, 4-linked side chains of which both may constitute a single molecule or either may be located on different molecules. The IG of strains Y5 contained higher proportions of α-1, 3, 6 branch and α-1, 6-linked residues than the S2-IG. Adherence of IG to glass was markedly inhibited by the presence of glucanases. Dextranase shortened the α-1, 6-linked, and mutanase the α-1, 3-linked linear chains in IG and thereby reduced the amounts of IG products and lowered their molecular size, which resulted in less stickiness and/or insolubility of the products.These results suggest that adhering deposits produced from sucrose by S. salivarius strains Y5 and S2 consist primarily of IG, and the α-1, 3- and α-1, 6-linked linear chains in IG, which are involved, respectively, in the water insolubility and adhesive property, act together to produce adherence of IG. Amounts of IG synthesized and relative proportion of the two linkages in IG determine the extent of adhesive mass formation. Thus, the glucanases would be effective to eliminate S. salivarius from various sites of the mouth, particularly the tongue dorsum and/or tooth surfaces.