The bacterial oxidation of aromatic compounds.

Evans (1947) observed that cultures of Vibrio 01 developing at the expense of phenol gave an intense violet Rothera reaction during the later stages of growth. The Rothera test is a nitroprusside reaction used clinically to detect the presence of "acetone bodies" (acetone and acetoacetic acid) in urine. Although Evans did not succeed in identifying the substance responsible for the positive Rothera reaction in cultures of Vibrio 01, he established the fact that it was an organic acid that was considerably less ether-soluble than acetoacetic acid. Subsequently Kilby (1948) isolated the acid from culture filtrates of Vibrio 01 and identified it as ,3-ketoadipic acid, a 6-carbon dicarboxylic acid. He concluded that it was an intermediate in the oxidation of the benzene ring. As reported in an earlier paper (Sleeper, Tsuchida, and Stanier, 1950), we have succeeded in obtaining dried cell preparations of Pseudomonasfluorescens capable of oxidizing catechol and protocatechuic acid. The dried cell preparations were found to attack both substrates with a much lower oxygen uptake per mole than that which occurs during the equivalent oxidations by living cells, a fact which suggested that the oxidations by dried cells are blocked at an early stage. The investigations reported in the present paper show that both aromatic compounds are converted quantitatively by dried cells into ,B-ketoadipic acid, thus confirming in a direct manner Kilby's inference that this aliphatic acid is an intermediate in the oxidations of aromatic compounds.