Sodium/proton antiport is required for growth of Escherichia coli at alkaline pH |
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Authors: | I McMorrow H A Shuman D Sze D M Wilson T H Wilson |
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Institution: | Department of Cellular and Molecular Physiology, Harvard Medical School, Boston, MA 02115. |
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Abstract: | Evidence is presented indicating that Escherichia coli requires the Na+/H+ antiporter and external sodium (or lithium) ion to grow at high pH. Cells were grown in plastic tubes containing medium with a very low Na+ content (5-15 microM). Normal cells grew at pH 7 or 8 with or without added Na+, but at pH 8.5 external Na was required for growth. A mutant with low antiporter activity failed to grow at pH 8.5 with or without Na+. On the other hand, another mutant with elevated antiporter activity grew at a higher pH than normal (pH 9) in the presence of added Na+ or Li+. Amiloride, an inhibitor of the antiporter, prevented cells from growing at pH 8.5 (plus Na+), although it had no effect on growth in media of lower pH values. |
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