Bacterial degradation of the nitrobenzoic acids. 2. Reduction of the nitro group

Abstract

has been observed. The fundamental importance of this reaction is emphasized by the work of de la Haba (1950) and McElroy & Spencer (1956), from which the suggestion arose that nitro compounds are probably intermediates in the reduction of nitrates by green plants and microorganisms , and the finding that moulds and higher plants, in the absence of added nitro compounds or their presumed precursors, elaborate enzymes capable of metabolizing nitro compounds (Bush, Touster & Brockman, 1951; Shimoda, 1951; Raistrick & St6ssl, 1958; Little, 1957). The appearance of arylamines in cultures of Nocardia species growing on nitrobenzoic acids was noted by Cain (1958a), but Cartwright & Cain (1959) found that these compounds appeared to have little significance in the oxidative breakdown of p-and m-nitrobenzoates, although this is less certain with the ortho-isomer. The study of the reduction of nitrobenzoates by Nocardia species and a strain of Pseudomona8 fluorescen8 described in this paper includes investigations with cell-free extracts and the stimulation of a nitroreductase by flavin adenine dinucleotide, an effect which had previously been observed only in E8cherichia coli among the bacteria (Saz & Martinez, 1956). EXPERIMENTAL Organi8m The organisms used were strains of Nocardia erythropolis, N. opaca, Nocardia M 1 and P8eudomona8fluore8cens isolated by enrichment methods and grown in bulk on a chemically defined medium by the techniques described by Cain (1958a). The procedures for obtaining adapted cells, washed suspensions and cell-free extracts were those described by Cartwright & Cain (1959). The particular strain of organisms

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

“…1), yet further analysis of the genes has shown that pnbA, encoding the primary reduction of 4NBen, is not located on either plasmid. However, there is substantial evidence that nitro groups can be reduced nonspecifically by a variety of dehydrogenase/reductase reactions (10,23,26,32), and in many situations where there are no specific degraders present, reduced derivatives often accumulate; this is particularly true in anaerobic environments where the nitro groups can be reduced completely to the corresponding amino groups (11). It is possible that nitroreductases in E. coli such as NfsA and NfsB (8,25,41,44) can effect the partial reduction of 4NBen, thus complementing pnbA and allowing PnbB on plasmids pTW3.11 and pTW3.12 to produce sufficient quantities of PCA to be visualized on the p-toluidine plates.…”

Purification and characterization of nitrobenzene nitroreductase from Pseudomonas pseudoalcaligenes JS45

“…The nitro anion radical reacts with oxygen to form superoxide and regenerate the parent nitro compound (6). Oxygen-insensitive (type I) enzymes reduce the nitro group in a series of two-electron transfers to produce the corresponding nitroso, hydroxylamino, and amino derivatives (9,40). Even though the nitroso intermediate is so reactive that it is difficult to isolate from biochemical reactions, its role can be inferred from studies of nitro compounds reduced in controlled chemical reactions (11).…”

Type I nitroreductases in soil enterobacteria reduce TNT (2,4,6-trinitrotoluene) and RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine)

“…Sub strates for these enzymes range from the nitrofuran antibiot ics to nitroarenes such as 1-nitropyrene, and also include nitroaromatic explosives such as 2,4,6-trinitrotoluene (TNT). The compounds most commonly observed during nitroreduction of nitroaromatics are aromatic hydroxylamines (Cartwright et al 1959;Kaplan 1990;McCalla et al 1970;McCormick et al 1976;Mori et al 1984;Schackmann and Müller 1991;Schenzle et al 1999). However, evidence does exist for the formation of a nitroso functional group during biological reduction of some nitroaromatics (Liu et al 1984).…”