[Biphasic energy-dependent potassium ion absorption by Escherichia coli cells]

The E. coli cells remove acid and accumulate potassium ions in two phases in the presence of glucose. The first phase (5-7 min) takes place only with an increase of external osmolarity; the second phase begins after 20 min and is not sensitive to alteration of the osmotic pressure. Potassium efflux occurs between two phases of K+-accumulation in alkaline media. Replacement of glucose by lactate results in a decrease of the first phase and abolition of the second one. The initial rate of K+-uptake for the first phase is a saturation curve in the range of 6 mM of external potassium concentration. These data indicate that the osmosensitive system of K+-uptake is connected with the first phase.