Effect of Electrolytes on the Uptake by Bacteria of Labelled Glutamate

Abstract

IN a recent paper, Krebs, Whittam and Hems¹ reported an accelerating effect of potassium salts on the rate of oxidation of various substrates by Alcaligenes faecalis. All the potassium salts tested were equally active. The ionic composition of the medium was found to affect respiration also in Escherichia coli (strain B), and Pasteurella tularensis (strain S + D)². The effect of the anion was also apparent with these two micro-organisms. For the maximal rate of oxidation of glutamate and glucose by P. tularensis the halogen salts of potassium and rubidium were found to be required; in the case of E. coli potassium chloride or sulphate was needed. In E. coli addition of minute amounts (10⁻⁴ M) of sodium salts rendered the accelerating effect of potassium independent of the nature of the anion. Conditions known to diminish the rate of penetration of metabolites into the bacterial cell (rising pH, low substrate concentration) rendered the accelerating effect of potassium more pronounced. The latter observation suggested regulation of permeability as a possible mode of action of the electrolytes. In order to test the validity of this assumption, the effect of electrolytes on the rate of uptake of labelled glutamate was examined.