Glycollate Inhibition of Growth of Pseudomonas aeruginosa on Lactate Medium

Summary: Glycollate inhibited growth of Pseudomonas aeruginosa in media containing either pyruvate or lactate as carbon sources. Glycollamide, but not glyoxylate, showed similar effects. Spontaneous mutants (L/G strains) were isolated that were able to grow on lactate medium in the presence of glycollate: their growth in pyruvate medium was still inhibited by glycollate. Synthesis of membrane-bound NAD+-independent D(−)- and L(+)-lactate dehydrogenases (iLDHs) was inducible by D- or L-lactate in the parent strain but was constitutive in the L/G strains. Glycollate inhibited induction of the synthesis of iLDHs in the parent strain growing in succinate medium but had no effect under the same conditions on strain L/G1. Glycollate was a competitive inhibitor of L(+)-iLDH (K i = 11 mM). No differences were found in the kinetic properties of L(+)-iLDH in cell-free extracts from strain L/G1 and the parent organism. Glycollate appears to inhibit growth on lactate medium predominantly through prevention of lactate induction of iLDH synthesis.