Extrusion of Sodium and Hydrogen Ions as the Primary Process in Potassium Ion Accumulation by Streptococcus faecalis

AUTOR(ES)

Harold, F. M.

RESUMO

Glycolyzing cells of Streptococcus faecalis accumulate K+ with concurrent extrusion of equivalent amounts of H+ and Na+. An attempt was made to clarify the retionship between the movements of Na+ and K+. Sodium was displaced from cells glycolyzing in the presence of ammonia, diethylamine, tris(hydroxymethyl)aminomethane, and other nitrogenous cations; by contrast, K+ was completely retained. Accumulation of K+ by heterologous exchange for Na+ was not inhibited by antibiotics which facilitate diffusion of K+ across the membrane, but was blocked by proton conductors. The results indicate that extrusion of Na+ and H+ from the cells is a primary, energy-linked process which generates an electrical potential (interior negative); K+ accumulation occurs in response to this potential. Two mutants deficient in K+ accumulation and retention were examined in terms of this model. One mutant is apparently defective in exchange of K+ for H+. In the other mutant, exchange of K+ for Na+ is impaired.

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