The kinetics of potassium exchange in cells of Staphylococcus aureus

The kinetics of potassium exchange in cells of Staphylococcus aureus with ⁴²K⁺ as a tracer in the extracellular potassium phase, was investigated. In phosphate buffer and KCl, in the absence of glucose, results showed that equilibration of distribution of external specific radioactivity and internal specific radioactivity was not achieved because the cells continuously lose potassium. In the presence of glucose, however, results showed no loss of potassium from the cells, and the potassium phase in the cells remained stationary, so that an equilibrium between intracellular and extracellular specific radioactivity was achieved. Sodium azide and dinitrophenol, added in both the absence and presence of glucose, did not have any effect on exchange as compared with controls. If, however, DL-glyceraldehyde was added in the experiments in the presence of glucose, no utilization of the carbon source, and the same behaviour for the cells as in the absence of glucose, was observed. Incubation temperature has a marked effect: potassium-exchange rate is greatly decreased at a temperature of 4°. Increasing concentrations of potassium in the suspension medium did not affect the exchange rate for concentrations higher than 3–4 mequiv potassium per 1.