Clinical studies in Sweden have shown that the proportion of
sorbitol-utilizing strains of Streptococcus sanguis increases in
dental plaque from individuals using
sorbitol-containing products for prolonged periods. We have undertaken to study the metabolism of
glucose and
sorbitol by S. sanguis 160, isolated from a subject consuming
sorbitol-containing
chewing-gum 4 times a day for 4 years. Growth on
glucose was inhibited by the presence of
sorbitol in the growth medium and
sorbitol was utilized in the presence of
glucose, albeit, at a slower rate than
glucose. In addition, pulses of
glucose added to cultures growing on
sorbitol resulted in the expulsion of
sorbitol from the cell. In order to examine further the relationship of
sorbitol and
glucose, uptake assays were carried out with S. sanguis 160 grown in continuous culture (pH 7.0, dilution rate = 0.1 h-1) with
glucose,
sorbitol or
nitrogen (
sorbitol excess) limitations. The uptake of [14C]-
glucose by
sorbitol-limited cells, but not by
glucose-limited cells, was inhibited by
sorbitol, as was glycolysis. Kinetic experiments with
glucose-limited cells showed 2 transport systems for
glucose with Ks values of 5.2 and 40 microM, and
glucose phosphorylation activity by decryptified cells indicated transport by the P-enolpyruvate (PEP)
phosphotransferase system (PTS) with lesser activity for an
ATP-dependent transport process. Transition from
glucose-limited growth to
sorbitol-limited growth revealed repression of total [14C]-
glucose uptake by intact cells and activity for
Enzyme II for
glucose (Ellglc) of the PTS measured in membrane preparations in the presence of an excess of the soluble PTS
proteins in crude cell-free supernatant fractions.(ABSTRACT TRUNCATED AT 250 WORDS)