The Microbial Metabolism of Nitro-aromatic Compounds

Abstract

Species of Nocardia and Pseudomonas, capable of oxidatively metabolizing nitrobenzoic acids and other aromatic compounds, were isolated from soil and polluted streams. The nitro group was eliminated principally as ammonia and arylamine but some nitrite appeared. The oxidation of both 0-and p-nitrobenzoic acids was adaptive and was competitively inhibited by the m-isomer.

Induction of an Anthranilate Oxidation System During the Metabolism of ortho-Nitrobenzoate by Certain Bacteria

“…A similar ready loss of the inducible enzyme system for o-nitrobenzoate oxidation in N . opaca (Cain, 1958) also occurred upon the exhaustion of the available substrate. It is obvious that in this particular case, the time of sampling would appreciably alter the conclusions to be drawn from sequential induction experiments regarding the significance of anthranilic acid as an intermediate in o-nitrobenzoate acid oxidation.…”

“…The growth medium for these experiments contained yeast extract; ammonia also appeared as a metabolic product (Cain, 1958;Cartwright & Cain, 1959a). Both of these N-sources might be held responsible for the rapid appearance of the anthranilate oxidase and the high concentrations of this enzyme which developed as the result of the metabolic production of anthranilic acid in growing cultures (see Fig.…”

“…Previous work (Cain, 1958;Cartwright & Cain, 1959a, b) showed that the pand m-aminobenzoic acids are not intermediates on the direct pathway of oxidative degradation of the corresponding nitrobenzoic acid isomers by nocardia species, but are produced by a reductive side reaction which operates concurrently (Cain & Cartwright, 1960 b). At that time the situation in Nocardia opaea with regard to the o-isomer was not clear though Ke, Gee & Durham (1959) had found that growth of a flavobacteriurn on o-nitrobenzoate did not sequentially induce the enzymes to oxidize anthranilate.…”

“…Because the growth of Nocardia opacu and the flavobacterium results in the production of a deep reddish-brown coloration of the medium, it was necessary to observe the precautions detailed previously (Cain, 1958) in making extinction measurements in cultures of these organisms. The approximate generation times of these organisms in o-nitrobenzoic acid medium supplemented with yeast extract were: N. opua, 3.5 hr; the flavobacterium, 1-5 hr; the Oklahoma isolate, 3.8 hr, the pseudomonad, 1.5 hr.…”

“…Anthranilic acid was estimated by diazotization (Glazko, Wolf & Dill, 1949) and o-nitrobenzoic acid by the quantitative chromatographic method used originally with the p-isomer (Cain, 1958). Where o-nitrobenzoic acid and anthranilic acid were present together in similar amounts, their respective concentrations could be calculated from their molecular extinctions at 268 and 240 m,u by solving the simultaneous equations provided by direct measurement, on suitably diluted samples, of the extinctions of the test solution a t these wavelengths.…”