Succinate transport in Bacillus subtilis. Dependence on inorganic anions

Cations were generally ineffective in stimulating succinate transport in a succinate dehydrogenase mutant of Bacillus subtilis unless accompanied by polyvalent anions; phosphate and sulfate being particularly active. The Km values for the phosphate or sulfate requirement were approx. 3 mM. Biphasic kinetics were characteristic of both the succinate (Km values 0.1 and 1 mM), and inorganic phosphate (Km values 0.1 and 3 mM) transport system(s). The phosphate transport system(s) was repressed by high inorganic phosphate and a coordinate increase in the transport of phosphate, arsenate, and phosphate-stimulated succinate transport accompanied growth in low phosphate media. A class of arsenate resistant mutants were simultaneously defective in the transport of arsenate, phosphate and succinate when cells were repressed for phosphate transport, however, the transport of these ions was regained in these mutants when grown in low phosphate media. Organic phosphate esters did not stimulate succinate transport in arsenate resistant mutants but were effective after growth in low phosphate media. Growth under phosphate limitation permitted the simultaneous regain of both phosphate and sulfate dependent succinate transport activities whereas sulfate limitation alone was ineffective. Succinate was not transported by an anion exchange diffusion mechanism since phosphate efflux was low or absent during succinate transport. The transport of C4-dicarboxylates in B. subtilis is strongly stimulated by intracellular polyvalent anions. The absence of an anion permeability mechanism precludes succinate transport but partial escape from this restriction is mediated by the derepression of a phosphate transport system.