Degradation of o-nitrobenzoate via anthranilic acid (o-aminobenzoate) by Arthrobacter protophormiae: a plasmid-encoded new pathway.

An Arthrobacter protophormiae strain RKJ100, isolated by selective enrichment, was capable of utilizing o-nitrobenzoate (ONB(+)) as the sole carbon, nitrogen, and energy source. The degradation of ONB proceeds through an oxygen insensitive reductive route as shown by the release of ammonia in the culture medium aerobically rather than nitrite ions. Thin-layer chromatography, gas chromatography, and gas chromatography-mass spectrometry of the intermediates have shown that ONB is degraded by a two-electron reduction of the nitro moiety, yielding o-hydroxylaminobenzoate and anthranilic acid. Quantitation of the intermediates, inhibition studies, and simultaneous induction studies have shown that anthranilic acid is produced as the terminal aromatic intermediate of a catabolic energy-yielding pathway and not as a side reaction taking place concurrently which is the first such report. A plasmid of approximately 65 kb was found to be responsible for harboring genes for ONB degradation in this strain. The same plasmid also encoded resistance to cobalt ions.