Potassium uptake of Alcaligenes faecalis

Abstract

Cells of A. faecalis lost most of their intracellular K when washed with distilled H2O. This treatment also removes most of the capacity to respire. Respiration is restored by the addition of K (and an oxidizable substrate) to the suspending medium. The restoration is accompanied by an uptake of K against a concentration gradient. The distribution of K between cells and medium was studied under a variety of conditions. Substantial amounts of K (up to 1.8 mg/ml of cells) are accumulated in the cells against concentration gradients. Accumulation also occurs anaerobically in the absence of substrates but the final gradients reached are lower than in respiring cells. Measurements of the simultaneous movements of K, Na and Cl show that the uptake of K is not accompanied by an equivalent movement of Cl or release of Na. How electroneutrality is maintained when K ions move was not established. The distribution of radioactivity between cells and medium after additions of K42 to the medium shows that the intracellular K exchanges readily with the K ions of the medium. The exchange was slightly more rapid aerobically than anaerobically. It is concluded that the organism contains a K-binding substance which behaves similarly to a colloid electrolyte or an ion-exchange resin.