THE EFFECT OF MAGNESIUM, POTASSIUM, AND IRON ON THE GROWTH AND MORPHOLOGY OF RED HALOPHILIG BACTERIA

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Abstract
Maximum growth of the red halophilic bacteria occurs in the presence of 3.0 to 5.0 M sodium chloride, 0.1 to 0.5 M magnesium ion, 50 to 100 p.p.m. (1.3 to 2.5 × 10−3 M) potassium ion, and 0.5 to 1.0 p.p.m. (1 to 2 × 10−5 M) ferrous ion. In magnesium deficient media the rod forms become coccoid. Some strains can be adapted to grow in low concentrations of magnesium (0.01 M) and these adapted strains retain a coccoid form even when transferred to higher concentrations of magnesium. Growth does not occur when potassium is removed from the medium. The potassium requirement may be satisfied by rubidium but not by cesium, lithium, or ammonium ions. Potassium partially replaces the sodium chloride requirement of the red halophiles.