Effect of pH upon sucrose and glucose catabolism by the various genogroups of Streptococcus mutans

Sucrose and glucose catabolism by seven strains of Streptococcus mutans belonging to six serotypes was assayed at pH's 6.5, 5.0, 4.5, and 4.0 with a radioisotopic tracer assay. The strains differed in their patterns of metabolic stimulation and inhibition at the different pH levels, falling into groups corresponding to the genetic groups described by Coykendall. The genogroup I (serotypes c and e) strains were the most acid-tolerant, having a pH optimum for lactic acid production at pH 5.0. These data furnish additional metabolic confirmation of the distinctiveness of these S. mutans subgroups.