Transport of tricarboxylic acids in Salmonella typhimurium.

Salmonella typhimurium possesses at least three inducible transport systems for the tricarboxylic acids (citric, isocitric, cis-aconitic, and tricarballylic). The first system was induced by citrate, isocitrate, or cis-aconitate, and transported citric acid and isocitric acid. The second system was also induced by the same acids as in the first system and transported cis-aconitic acid. This system required Mg(2+) ions and was stable at pH 8.4 but unstable at pH 7.0. The metal ion was replaced with Sr(2+) or Ca(2+) ions but not with Ba(2+) ions. The third system was induced by tricarballylate and transported citric acid, cis-aconitic acid, and tricarballylic acid.