Magnesium and anion requirements of rodB mutants of Bacillus subtilis

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Abstract
RodB mutants of B. subtilis require several hundred-fold more Mg2+ in a minimal growth medium than the wild type to achieve rapid growth. In the presence of all concentrations of Cl-, the organisms grow as deformed cocci, but with 10 mM Mg2+ and Br-, I- or NO3- present they grow as rods. The morphology is then directly under the control of the concentration of both Mg2+ and anion. Originally, it was found that L-glutamic acid in the medium brought about the change from deformed spheres to rods. This amino acid will similarly function at a much lower concentration when the higher concentrations of Mg2+ and Cl- are also present. At a constant concentration of L-glutamate, the morphology can be controlled by varying the Mg2+ concentration. In the presence of Mg2+ and I-, the morphological change is temperature sensitive. At 30.degree. C rods are formed and at 42.degree. C deformed cocci are formed. The requirement of a rodB mutant for a high Mg concentration and the round morphology are most probably due to a single mutation.