Study of regulation of acid excretion from the cells of plaque bacteria

点击翻译按钮获取中文摘要

(1). The effect of sodium and potassium ions on intracellular acid production and acid excretion by glycolyzing cells of Streptococcus mutans was examined. A pH-sensitive fluorescent dye, bis (carboxyethyl)-carboxyfluorescein allowed for the continuous monitoring of intracellular pH while proton excretion was measured simultaneously with a pH-stat. Sodium ions inhibited and potassium ions, at low pH,accelerated the amount of measurable acid excreted extracellularly.(2). In the presence of NaCl (0.15-0.30 M), the total amount of carboxylic acids excreted was inhibited by up to 31%. The intracellular level of fructose 1,6-bisphosphate increased by 58% and levels of 3- phosphoglycerate and pyruvate decreased by 46 and 12%, respectively. The intracellular pH decreased in the presence of sodium ions. It is possible that the low intracellular pH inhibits the activity of the glycolytic enzymes involved in the breakdown of fructose 1,6-bisphosphate to 3- phosphogycerate.(3). The cells grows at pH 5.5 excreted more protons and carboxylic acids than the cells grown at pH 7.0 from glucose. The acidic grown cells kept the intracellular pH higher than the neutral grown cells. These findings indicated that the excretion of acid increased when the cells were grown at acidic pH levels.(4). Under strictly anaerobic conditions, 0.025 mM NaF inhibited proton excretion by 50% in cells grown at pH 7.0 when the pH of reaction mixture was 5.0. Such levels of fluoride are about 10 to 20 times lower than that reported previously.(5). The inhibitory effect of chlorhexidine (0.025mM) alone, fluoride (0.05 mM to 0.4 mM) alone andc hlorhexidine-fluoride combination on proton excretion and intracellular pH in glycolyzing streptococcal cells were examined under different pH conditions. The chlorhexidine-fluoride combination had the advantage of anti-acidogenic effects at both acidic as well as neutral pH levels.