Insoluble glucans synthesized by cariogenic streptococci: a structural study.

Of the three cariogenic streptococci grown in four various culture media, the strain Streptococcus mutans 20,381 was found to produce large amounts of extracellular glucosyltransferase and water-insoluble, adhesive exopolysaccharide when grown in batch culture on brain-heart infusion broth. Methylation and nuclear magnetic resonance analyses revealed that the insoluble polymers synthesized by the crude glucosyltransferase preparations were mixed-linkage (1-->3), (1-->6)-alpha-D-glucans (so-called mutans) with a greater proportion of 1,3 to 1,6 linkages and major branch points of 3,6-linked glucose. The percentage content of different types of linkages in glucans varied widely and depended on the strain of cariogenic bacteria used to produce glucosyltransferase, and on the kind of medium utilized to cultivate mutans streptococci. The potential application of insoluble glucan produced by mutans streptococci is discussed.