Two major potassium uptake systems, KtrI and KtrII, in Enterococcus hirae

We isolated a mutant, JEMK1, which did not grow at pH 6.0 in medium contain ing 0.5 mM KCl, derived from a Enterococcus hirae mutant deficient in the K trII K+ uptake system. This mutant showed an impairment in the proton poten tial-dependent K+ uptake, the activity of the KtrI K+ uptake system, and di d not grow well in K+-poor media in a wide pH range from 6 to 10, suggestin g that KtrI and KtrII are the main systems for potassium accumulation of th is bacterium. (C) 1999 Federation of European Microbiological Societies. Pu blished by Elsevier Science B.V. All rights reserved.