pH Regulation by Streptococcus mutans

Abstract

The intracellular pH (pHi) optimum for glycolysis in Streptococcus mutans Ingbritt was determined to be 7.0 by use of the ionophore gramicidin for manipulation of pHi. Glycolytic activity decreased to zero as the pHi was lowered from 7.0 to 5.0. In contrast, glycolysis had an extracellular pH (pHo) optimum of 6.0 with a much broader profile. The relative insensitivity of glycolysis to the lowering of pHo was attributed to the ability of S. mutans to maintain a transmembrane pH gradient (ApH, inside more alkaline) at low pHo. At a pHo of 5.0, glycolyzing cells of S. mutans maintained a pH of1.37 ± 0.09 units. The maintenance of this ΔpH was dependent on the concentration of potassium ions in ..