A novel pathway for the catabolism of 4-nitrotoluene by Pseudomonas

Abstract

Eleven strains of Pseudomonas were isolated by selective enrichment on 4-nitrotoluene (4NT). They all utilized 4NT, 4-nitrobenzyl alcohol (4NBA) or 4-nitrobenzoate (4NBZate) as sole sources of carbon and nitrogen, One strain, TW3, was used for more detailed studies. 4NT-grown cells of TW3 take up 0, when incubated in the presence of 4NBA, 4-nitrobenzaldehyde (4NBZ) and 4NBZate. HPLC analysis of culture supernatants showed that 4NBZ and 4NBZate were formed when 4NT-grown cells were incubated with 4NBA, whereas only 4NBZate was found when they were incubated with 4NBZ. Two dehydrogenases were detected in extracts of 4NT-grown cells. 4NBA dehydrogenase could be assayed by a dye-linked assay whereas 4NBZ dehydrogenase activity was linked to NAD+ reduction. No nitrite was detected in supernatants of 4NBZate-grown cells incubated with 4NBZate but the nitrogen appeared as ammonium. The only aromatic ring-cleavage dioxygenase that was induced during growth on the nitroaromatics was protocatechuate 3,4-dioxygenase. It is proposed that the pathway for 4NT catabolism proceeds via 4NBA, 4NBZ and 4NBZate and ultimately to protocatechuate with release of the nitro group as ammonium.

Cloning and Characterization of the pnb Genes, Encoding Enzymes for 4-Nitrobenzoate Catabolism in Pseudomonas putida TW3

“…The initial reduction is to a hydroxylamino group via a nitroso intermediate. This can then undergo a mutase-mediated rearrangement to ortho-aminophenols (as in the cases of nitrobenzene [31], 3-nitrophenol [37,38], and 4-chloronitrobenzene [21]) with the later release of ammonia; alternatively, the hydroxylamino compound can be converted directly to the corresponding catechol by a lyase-mediated reaction with direct elimination of ammonia, such as in the degradation of 4-nitrobenzoate (14,15,43), 4-nitrotoluene (16,35), and 3-nitrophenol (27).…”

“…During the catabolism of 4-nitrotoluene in Pseudomonas putida strain TW3 (35), the nitro group is retained during the sequential oxidation of the methyl group to form 4-nitrobenzoate (4NBen). The genes encoding the enzymes for the initial steps in the catabolism of 4-nitrotoluene to 4NBen are very similar in sequence and organization to the TOL plasmidencoded upper pathway genes of toluene catabolism (42), with the addition of a novel NAD(P) ϩ -independent alcohol dehydrogenase (18,19).…”

Isolation and Characterization of a 4-Nitrotoluene-Oxidizing Enzyme from Activated Sludge by a Metagenomic Approach

“…A 4-NT-degrading enzyme from Pseudomonas sp. strain TW3 has been characterized (36). In this strain, the methyl group of 4-NT is initially oxidized to form 4-nitrobenzyl alcohol by a twocomponent enzyme, 4-NT monooxygenase, consisting of a hydroxylase (NtnM) and a reductase (NtnA) (20).…”

Federal Integrated Biotreatment Research Consortium (FIBRC): Flask to Field Initiative

“…Bacteria able to utilize 2-NT Haigler et al, 1994b), 4-NT (Haigler andHe and Spain, 2000b;, 2,4-DNT Haigler et al, 1994a;Spanggord et al, 1991), and 2,6-DNT as sole carbon and nitrogen sources have been isolated and the degradative pathways determined. Multiple pathways for 4-NT degradation, all involving an initial reduction, have been identified (Haigler and Spain, 1993;Rhys-Williams et al, 1993; in three different bacteria (Fig. 4).…”