Bacterial degradation of the nitrobenzoic acids

Abstract

Nocardia erythropolis and N. opaca oxidize p-nitrobenzoate and o-nitrobenzoate respectively to CO2 and NH3; Nocardia M 1 produces nitrite but no NH3 from the meta-isomer. The effects of some inhibitors on these oxidations are described. N. erythropolis and Nocardia M 1 convert their respective nitrobenzoate substrate into the corresponding hydroxy compound and thence to protocatechuate. N. erythropolis also produces 4-nitrocatechol from p-nitrobenzoate. N. erythropolis and Nocardia M 1 grown upon p-and m-nitrobenzoate respectively, but not upon glucose or nutrient broth, possess the enzyme systems for the oxidation of protocatechuate. Freeze-dried cells and crude extracts convert protocatechuate quantitatively into [beta]-oxoadipic acid. Certain desiccator-dried preparations oxidize this keto acid, the more active ones finally yielding succinate. All the protocatechuic acid oxidas.e activity is in the soluble-protein fraction of crude extracts and can be separated from decarboxylase activity by fractionation with ammonium sulphate, the oxidase activity lying in the fraction precipitating between 0.33 and 0.45 saturation. The end product of partially purified oxidase in [beta]-carboxymuconic acid. Dried cells of N. opaca oxidize o-nitrobenzoate catechol and protocatechuate rapidly. The possible explanations for the differences in nitrogenous end-products are discussed and attention is drawn to the analogous reactions performed by Nocardia spp. grown on the nitrobenzoates and by other micro-organisms grown on a variety of ring compounds.