[Role of sodium ions in the absorption of C4-dicarboxylic acids by Ectothiorhodospira shaposhnikovii].

The uptake of C4-dicarboxylic acids by the phototrophic purple bacterium Ectothiorhodospira shaposhnikovii, strain 1K, involves a common transport system obligatorily dependent on sodium ions. The values of Km for the transport of succinate, malate and fumarate are 1-10(-7), 3-10(-7) and 8-10(-7) M, respectively. The transport of C4-dicarboxylic acids in an energy-dependent process; it is inhibited by m-chlorocarbonylcyanide phenylhydrazone. It has been proved that the uptake of C4-dicarboxylic acids depends on sodium ions because the latter are required for symport. The effect of membrane potential (inside negative) on succinate uptake driven by an artificial sodium gradient was dependent on pH. At pH 7.0 the uptake was inhibited by membrane potential, but was stimulated by it at pH 9.0. The cells of E. shaposhnikovii grown under the autotrophic conditions maintain the capability to take up C4-dicarboxylic acids.