NUTRITION AND METABOLISM OF MARINE BACTERIA. XIII. INTRACELLULAR CONCENTRATIONS OF SODIUM AND POTASSIUM IONS IN A MARINE PSEUDOMONAD

Abstract

Takacs, Frank P. (McGill University, Montreal, Quebec, Canada), Tibor I. Matula, and Robert A. MacLeod. Nutrition and metabolism of marine bacteria. XIII. Intracellular concentrations of sodium and potassium ions in a marine pseudomonad. J. Bacteriol. 87:510-518. 1964.-Washed cells of a marine pseudomonad were suspended in buffered salt solutions containing, in addition to MgSO(4), NaCl and KCl at various concentrations. The cells were centrifuged from the medium and analyzed for Na(+) and K(+). Inulin and C(14)-carboxypolyglucose were employed to estimate the volume of extracellular fluid associated with the packed cells. Intracellular Na(+) and K(+) concentrations were determined by correcting for the amount of Na(+) and K(+) in the extracellular fluid. At all levels of Na(+) in the suspending medium (0 to 1 m), the intracellular and extracellular Na(+) concentrations within the limits of experimental error were the same. The intracellular K(+) concentrations were approximately double the extracellular concentrations at the two levels of K(+) tested (0.01 and 0.15 m) and were not influenced by the amount of Na(+) present. Intracellular and extracellular Cl(-) concentrations were the same at the one level of Cl(-) examined. The intracellular fluid volume varied with the NaCl or KCl concentration of the suspending medium, being greatest in the absence of added salts, decreasing to a minimum at 0.3 m salt, and then increasing slightly at higher salt concentrations. Most of the intracellular Na(+) could be removed by washing with solutions of MgSO(4) or sucrose, but a small amount [10 to 15 mumoles/g (dry weight)] remained bound to the cells.