Oxalate and formate in Alcaligenes and Pseudomonas species

Oxalate is metabolized by the glycerate pathway involving glyoxylate carboligase in Alcaligenes LOx and Pseudomonas KOx, and by the serine pathway involving hydroxypyruvate reductase in Ps.MOx and Ps.AM1 (var. 470). Although A.LOx does not grow on formate, stimulation of growth was observed in the presence of amino acids and a few Kreb's cycle intermediates. A.LOx possesses two different mechanisms for the oxidation of formate: (1) the constitutive formate oxidase which is present in the particulate fraction of oxalate-grown and succinate-plus-formate-grown cells; (2) the inducible NAD-linked formate dehydrogenase present in the 100 000 x g supernatant fraction of the cell-free extracts of oxalate-grown cells alone. The two systems occur simultaneously in oxalate-grown cells. The effect of inhibitors on formate oxidase activity and the other enzyme activities of the particulate formate-oxidizing fraction indicate that the oxidation of formate is linked to the respiratory chain.