Reduction of Acidurance of Streptococcal Growth and Glycolysis by Fluoride and Gramicidin

Abstract

The acidurance of glycolysis by intact cells of Streptococcus mutans GS-5, Streptococcus salivarius ATCC 25925, and Streptococcus sanguis NCTC 10904 was found to be highly dependent on membrane functions affected by gramicidin, which increases the proton permeability of cell membranes. Plots of % glucose utilized during two hours against suspension pH values for cells suspended in 100 mM phosphate buffer plus 1 mM MgCl2 plus 13.9 mM glucose indicated, for 50% glucose utilization, pH values of 5.0 for S. mutans, 5.7 for S. salivarius, and 6.2 for S. sanguis. Gramicidin treatment shifted these values to 6.0, 6.3, and 6.9, respectively. Growth of S. mutans and S. salivarius in complex media proved to be more acid-sensitive than was glycolysis, and in batch cultures, there was a well-defined, post-growth phase of glycolysis. Minimum pH values for growth and for glycolysis in medium with excess glucose were approximately 4.8 and 4.4, respectively, for S. mutans, and 4.9 and 4.3 for S. salivarius. S. sanguis was less aciduric and showed little differential acid sensitivity, with minimum pH values of about 5.2 for both growth and glycolysis. Fluoride acted to eliminate the differences in acidurance of growth and glycolysis for S. mutans or S. salivarius and to render both processes more acid-sensitive. Thus, glycolysis was more fluoride-sensitive than was growth. Growth was found to be acid-limited in media with initial glucose levels greater than 0.2, 0.3, and 0.5% (weight/volume) for S. sanguis, S. mutans, and S. salivarius, respectively, and to be glucose-limited at lower levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Modification of Gene Expression and Virulence Traits in Streptococcus mutans in Response to Carbohydrate Availability

“…Thus, the loss of ManL dramatically impacts glycolytic rates when cells are grown in limiting glucose. Also of note, the terminal pH achieved in the pH drop assay is strongly correlated with acid tolerance (17,41,42), with the lower pH being associated with greater acid tolerance. The fact that cells that lacked ManL and that were limited for glucose could not achieve as low a terminal pH as the wild-type strain grown under the same conditions implicates ManL as a potential contributor to or regulator of acid tolerance.…”

“…Rapid fermentation of sugars by S. mutans can cause a substantial drop in the pH of oral biofilms, from neutral pH to values well below 5 (16). The acidic environment created by carbohydrate fermentation favors the growth of S. mutans over that of health-associated, acid-sensitive commensal organisms, because S. mutans is well adapted to survive and continues to metabolize carbohydrates at low pH (17).…”

Uptake and Metabolism of N -Acetylglucosamine and Glucosamine by Streptococcus mutans

“…The enhanced capacity of cells grown with glucose alone or a combination of glucose and GlcNAc to lower the pH when exogenous glucose was provided may be explained as follows. Previous studies have demonstrated that exposure to a moderately acidic environment (e.g., pH 5.5 for 2 h) is correlated with enhanced acid tolerance, attributable to the induction of the adaptive acid tolerance response (ATR) (60,(84)(85)(86)(87). Two hallmarks of induction of the ATR in S. mutans are more rapid metabolism of carbohydrate and attainment of a lower final pH in pH drop assays.…”

Effects of a coating resin containing S-PRG filler to prevent demineralization of root surfaces

“…This may be the result of fluoride release from the coating material. Fluoride can reduce acid production by S. mutans through a number of mechanisms 50) , including inhibition of the glycolytic enzyme enolase 51,52) and the proton-extruding ATPase 53,54) . The reduced drop of pH on the surface of PRG Barrier Coat could also be related to interference with other intracellular or plaque-associated enzymes in S. mutans, such as acid phosphatase, pyrophosphatase, peroxidase and catalase by released fluoride 55) .…”