A novel degradative pathway of 2-nitrobenzoate via 3-hydroxyanthranilate in Pseudomonas fluorescens strain KU-7

A bacterial strain KU-7, identified as a Pseudomonas fluorescens by 16S rDN A sequencing, was one of the 12 new isolates that are able to grow on 2-nit robenzoate as a sole source of carbon, nitrogen, and energy. Resting cells of KU-7 were found to accumulate ammonia in the medium indicating that degr adation of 2-NBA proceeds through a reductive route. Metabolite analyses by thin layer chromatography and high pressure liquid chromatography indicate d that 3-hydroxyanthranilate is an intermediate of 2-nitrobenzoate metaboli sm in KU-7 cells. This offers an alternative route to 2-nitrobenzoate metab olism since anthranilate (2-aminobenzoate) or catechol were detected as int ermediates in other bacteria. Crude extracts of KU-7 cells converted 2-nitr obenzoate to 3-hydroxyanthranilate with oxidation of 2 mol of NADPH. Ring c leavage of 3-hydroxyanthranilate produced a transient yellow product, ident ified as 2-amino-3-carboxymuconic 6-semialdehyde, that has a maximum absorb ance at 360 nm. The initial enzymes of the 2-nitrobenzoate degradation path way were found to be inducible since succinate-grown cells produced very lo w enzyme activities. A pathway for 2-nitrobenzoate degradation in KU-7 was proposed. (C) 2000 Federation of European Microbiological Societies. Publis hed by Elsevier Science B.V. All rights reserved.