Effect of endogenous phosphoenolpyruvate potential on fluoride inhibition of glucose uptake by Streptococcus mutans.

The fluoride sensitivity of glucose uptake by whole cell suspensions of Streptococcus mutans was studied. Preincubation of the organism with up to 1 mM glucose markedly reduced the fluoride sensitivity of subsequent glucose uptake at pH 7.0 and 5.5. Glucose preincubation was shown to result in the establishment of a stable pool of three-carbon glycolytic intermediates. On the basis of inhibition studies and thin-layer chromatography of cell extracts, we suggest that 3- and 2-phosphoglycerate are the principal constituents of the pool. Increased concentrations of glucose used in preincubation mixtures was associated with increased pool sizes of the glycolytic intermediates and increased fluoride resistance. Transport of 2-deoxy-D-glucose by permeabilized cells was inhibited by fluoride when 2-phoshoglycerate served as the energy source. Increased concentrations of 2-phosphoglycerate were shown to overcome the fluoride inhibition of transport. The data suggest that establishment of a stable pool of glycolytic intermediates that includes 2-phosphoglycerate (or its progenitors) may contribute significantly to the apparent refractoriness of plaque microbes to fluoride in vivo.