Gary R. Bender

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

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 MgCl 2 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. When 1.0 mM NaF was added to the media, the acid-sensitizing effect of fluoride was evident in major shifts in the initial glucose levels for transition from glucose-limited to acid-limited growth to 0.1 and 0.2% for S. mutans and S. salivarius, respectively. S. sanguis was less severely affected by fluoride. Fluoride treatment of glycolyzing cells of S. mutans at a pH value of 5 resulted in little change in intracellular levels of phosphoenolpyruvate but increased levels of 2-phosphoglycerate, indicative of inhibition of intracellular enolase. However, there were also large decreases in levels of early glycolytic intermediates, to about the levels found in starved cells, presumably due to fluoride inhibition of glucose uptake.

Inhibitory and cidal antimicrobial actions of electrically generated silver ions

One promising alternative to antibiotics in the treatment of localized infections is the generation of antimicrobial silver ions by the use of low intensity direct current from a pure silver anode implanted at the site of an infection. This study investigates the in vitro bacteriostatic and bactericidal properties of this system on a variety of organisms.

Bacteriolytic Action of Fluoride Ions

Bacillus subtilis, Neisseria subflava, and LYT coccus were found to undergo massive lysis after growth in media containing 0.01 to 10 mM NaF. When cells of these organisms were transferred from late-exponential-phase cultures to 0.02 M sodium phosphate buffer plus 0.1 M KCl, they underwent spontaneous autolysis. Cells grown in media with fluoride were more liable to autolysis, and walls isolated from them also showed enhanced autolytic sensitivity, even though added fluoride did not directly stimulate autolysins. Sporadic or partial lysis occurred in populations of Streptococcus sanguis and Streptococcus mutans BHT or LM-7 after growth in fluoridated media. Most bacteria that were tested did not undergo fluoride-induced lysis. However, cells of all test bacteria were found to have reduced amounts of peptidoglycan per unit of cell weight when grown in the presence of fluoride. Incorporation of labeled lysine or glucosamine into peptidoglycan (Park-Hancock residue) was stimulated, instead of inhibited, by fluoride. However, fluoride also stimulated the loss of radioactivity from Park-Hancock residues of cells that had previously incorporated labeled lysine or glucosamine. Thus, fluoride appeared to enhance peptidoglycan turnover, and this turnover reduced the peptidoglycan contents of all bacteria tested, but induced lysis in only those bacteria that normally have highly active autolytic systems.

Coordinately repressible arginine deiminase system inStreptococcus sanguis

Arginine catabolism byStreptococcus sanguis NCTC 10904 was found to involve the arginine deiminase system. Enzyme assays indicated that the system was coordinately repressed by glucose and sucrose. Arginine transport also was repressed but not completely. A barotolerant variant of the organism was found to have a regulatory system defective for glucose repression so that ammonia was produced from arginine in cultures of the variant at atmospheric pressure even when the bacteria were producing acid glycolytically.

In vitro effects of low intensity direct current generated silver on eukaryotic cells

An examination of the effects of low intensity direct current generated silver, (LIDC Ag) on several types of eukaryotic microorganisms and cell culture lines suggests that LIDC Ag has an appropriate selective toxicity for prokaryotic cells. It appears that levels of this agent could be obtained clinically that would have marked bacteriostatic activity and yet have little or no effect on mammalian cells.

Reversible fluoride uptake and release byStreptococcus mutans GS-5 and FA-1

Concentrative uptake of fluoride by cells ofStreptococcus mutans in thick suspensions was found to be a reversible process responsive to changes in ΔpH across the cell membrane imposed by rapid acidification or neutralization of the suspensions. The cells were found to be permeable to fluoride in media of neutral pH but to concentrate it only in acid media.