Studies on the Fate of the Glucosyl Moiety of Sucrose Metabolized by Streptococcus mutans

Streptococcus mutansl"2 and dietary sucrose have been implicated in multisurface caries of the teeth of rodents and primates, in-cluding man3-6; glucan synthesis by S mu-tans in the presence of sucrose has been implicated in the adhesion of these micro-organisms to tooth surfaces.",7-9 Recent studies'0 have shown that although only the glucosyl moiety of sucrose is synthesized into cell surface and extracellular glucans, only a small amount of all the glucosyl moieties is so polymerized and the bulk is fermented to acid products typical of homo-fermentative microorganisms. Thus, the glu-cosyl moiety of sucrose is neither wholly polymerized nor wholly fermented. Studies of the growth of S mutans in the presence of sucrose have indicated that both its rate of growth and its growth yield are restricted as the sucrose concentration of the medium is elevated,'1 contrary to the expected substrate-molar-growth-yield rela-tionship.'2 These data suggested that en-vironmental sucrose concentration is a po-tent determinant of the distribution of the glucosyl portion of sucrose between fermen-tative and glucan-synthetic fates. The pres-ent studies examine the distribution of the glucosyl moiety of sucrose metabolized by intact cells of S mutans as affected by the environmental concentration of sucrose.