SIMULTANEOUS MONITORING OF INTRACELLULAR PH AND PROTON EXCRETION DURING GLYCOLYSIS BY STREPTOCOCCUS-MUTANS AND STREPTOCOCCUS-SANGUIS - EFFECT OF LOW PH AND FLUORIDE

A system was developed by which 2',7'-bis(carboxyethyl)-4 or 5-carboxy fluorescein could be used to monitor intracellular pH at the same time that proton excretion was being measured. Streptococcal cells were lo aded with the dye, and after the addition of glucose protons were excr eted and the intracellular pH increased quickly and remained higher th an the extracellular pH of 7.0. The excretion of protons stopped and t he intracellular pH returned to the original level when glucose was de pleted. The intracellular level of ATP remained high during glucose me tabolism and decreased with the depletion of glucose. At extracellular pH of 5.5, and 5.0, the intracellular pH of fasting cells was higher than the extracellular pH value. After addition of glucose there were initial lags of proton excretion and of increases in intracellular pH at the acidic extracellular pH values. In the presence of fluoride, a lag in proton excretion and a simultaneous decrease in intracellular p H were observed, indicating a partial and transient inhibition of prot on-ATPase activity.