CATION-PROTON ANTIPORT SYSTEMS IN ESCHERICHIA-COLI - ABSENCE OF POTASSIUM-PROTON ANTIPORTER ACTIVITY IN A PH-SENSITIVE MUTANT

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  • 1 January 1980
    • journal article
    • research article
    • Vol. 255  (9) , 3824-3825
Abstract
Alkaline-sensitive strains of E. coli were selected by mutagenesis followed by penicillin killing in medium at pH 8.3. One stain lacked K+/H+ exchange. At neutral pH, the doubling time of the mutant was not significantly different from that of the parent, but at pH 8.3 the doubling time of the mutant increased over 5-fold. No energy-dependent uptake of 204Tl+ was observed in the mutant, but addition of the K+/H+ exchanger Nigericin resulted in identical 204Tl+ uptake in the mutant and parent. These results are consistent with the hypothesis that the K+/H+ antiporter is responsible for regulation of cytosolic pH in E. coli. In the absence of antiporter, the organism would be unable to grow at alkaline pH due to alkalinization of the cytosol.