Intracellular flux of glucose metabolism in streptococcal cells by simultaneous monitoring of fluorescence dependent on reduced nicotinamide adenine nucleotide and acid excretion under strictly anaerobic conditions.

Abstract

Reduced nicotinamide adenine nucleotide (NADH)-dependent fluorescence and acid excretion during glucose pulse to washed Streptococcus mutans cells were monitored simultaneously at pH 7.0 with a fluorescence spectrophotometer and a pH-stat. Acid excretion started with addition of glucose. At the same time, the fluorescence dropped quickly to a minimum level and increased to a plateau level, suggesting that pyruvate metabolism started immediately after addition of glucose, then the rate of the pyruvate metabolism became almost equal to the rate of glycolysis. When the acid excretion stopped, the fluorescence increased rapidly from the plateau to the maximum level, suggesting that the pyruvate metabolism stopped first, and then began to decrease to the original level. The system used in this study for simultaneously monitoring the level of NADH and acid excretion gives us a crucial tool to clarify a biochemical mechanism of the control of sugar metabolism by streptococci.