Initial reductive reactions in aerobic microbial metabolism of 2,4,6-trinitrotoluene.

Because of its high electron deficiency, initial microbial transformations of 2,4,6-trinitrotoluene (TNT) are characterized by reductive rather than oxidation reactions. The reduction of the nitro groups seems to be the dominating mechanism, whereas hydrogenation of the aromatic ring, as described for picric acid, appears to be of minor importance. Thus, two bacterial strains enriched with TNT as a sole source of nitrogen under aerobic conditions, a gram-negative strain called TNT-8 and a gram-positive strain called TNT-32, carried out nitro-group reduction.

A stereoselective carbon-nitrogen lyase from Ralstonia sp. SLRS7 cleaves two of three isomers of iminodisuccinate.

Following biodegradation tests according to the OECD guidelines for testing of chemicals 301F different degradation rates were observed for the three stereoisomers of iminodisuccinate (IDS). A strain was isolated from activated sludge, which used two of three isomers, R,S-IDS and S,S-IDS, as sole source of carbon, nitrogen, and energy. The isolated strain was identified by 16S-rDNA and referred to as Ralstonia sp.

Biodegradation of all stereoisomers of the EDTA substitute iminodisuccinate by Agrobacterium tumefaciens BY6 requires an epimerase and a stereoselective C-N lyase.

Biodegradation tests according to Organization for Economic Cooperation and Development standard 301F (manometric respirometry test) with technical iminodisuccinate (IDS) revealed ready biodegradability for all stereoisomers of IDS. The IDS-degrading strain Agrobacterium tumefaciens BY6 was isolated from activated sludge. The strain was able to grow on each IDS isomer as well as on Fe(2+)-, Mg(2+)-, and Ca(2+)-IDS complexes as the sole carbon, nitrogen, and energy source.

Nitrite elimination and hydrolytic ring cleavage in 2,4,6-trinitrophenol (picric acid) degradation.

Two hydrogenation reactions in the initial steps of degradation of 2,4,6-trinitrophenol produce the dihydride Meisenheimer complex of 2,4,6-trinitrophenol. The npdH gene (contained in the npd gene cluster of the 2,4,6-trinitrophenol-degrading strain Rhodococcus opacus HL PM-1) was shown here to encode a tautomerase, catalyzing a proton shift between the aci-nitro and the nitro forms of the dihydride Meisenheimer complex of 2,4,6-trinitrophenol. An enzyme (which eliminated nitrite from the aci-nitro form but not the nitro form of the dihydride complex of 2,4,6-trinitrophenol) was purified from the 2,4,6-trinitrophenol-degrading strain Nocardioides simplex FJ2-1A.

Homologous npdGI genes in 2,4-dinitrophenol- and 4-nitrophenol-degrading Rhodococcus spp.

Rhodococcus (opacus) erythropolis HL PM-1 grows on 2,4,6-trinitrophenol or 2,4-dinitrophenol (2,4-DNP) as a sole nitrogen source. The NADPH-dependent F(420) reductase (NDFR; encoded by npdG) and the hydride transferase II (HTII; encoded by npdI) of the strain were previously shown to convert both nitrophenols to their respective hydride Meisenheimer complexes. In the present study, npdG and npdI were amplified from six 2,4-DNP degrading Rhodococcus spp.

Molecular cloning and characterization of the gene coding for the aerobic azoreductase from Xenophilus azovorans KF46F.

The gene coding for an aerobic azoreductase was cloned from Xenophilus azovorans KF46F (formerly Pseudomonas sp. strain KF46F), which was previously shown to grow with the carboxylated azo compound 1-(4'-carboxyphenylazo)-2-naphthol (carboxy-Orange II) as the sole source of carbon and energy. The deduced amino acid sequence encoded a protein with a molecular weight of 30,278 and showed no significant homology to amino acid sequences currently deposited at the relevant data bases.

Bioelimination of trinitroaromatic compounds: immobilization versus mineralization.

Electron deficiency of trinitroaromatic compounds favors gratuitous reduction of nitro groups or unique ring hydrogenation. From nitro-group reduction of 2,4,6-trinitrotoluene (TNT), some highly reactive products are generated that are subject to further transformation or interaction with diverse electrophiles. Up to now, only initial ring hydrogenation of picric acid (2,4,6-trinitrophenol) opens perspectives of complete degradation.

Effects of different quinoid redox mediators on the anaerobic reduction of azo dyes by bacteria.

The addition of quinoid redox mediators to anaerobically incubated cultures of various taxonomically different bacterial species resulted in significantly increased reduction rates for the azo dye amaranth. From different quinones tested, generally anthraquinone-2-sulfonate (AQS) and lawsone (2-hydroxy-1,4-naphthoquinone) caused the highest increase in the azoreductase activities. The effects of AQS and lawsone were studied in greater detail with Sphingomonas xenophaga BN6 and Escherichia coli K12.

Converging catabolism of 2,4,6-trinitrophenol (picric acid) and 2,4-dinitrophenol by Nocardioides simplex FJ2-1A.

Initial F420-dependent hydrogenation of 2,4,6-trinitrophenol (picric acid) generated the hydride sigma-complex of picrate and finally the dihydride complex. With 2,4-dinitrophenol the hydride sigma-complex of 2,4-dinitrophenol is generated. The hydride transferring enzyme system showed activity against several substituted 2,4-dinitrophenols but not with mononitrophenols.

npd gene functions of Rhodococcus (opacus) erythropolis HL PM-1 in the initial steps of 2,4,6-trinitrophenol degradation.

Rhodococcus (opacus) erythropolis HL PM-1 grows on 2,4,6-trinitrophenol (picric acid) or 2,4-dinitrophenol (2,4-DNP) as sole nitrogen source. A gene cluster involved in picric acid degradation was recently identified. The functional assignment of three of its genes, npdC, npdG and npdI, and the tentative functional assignment of a fourth one, npdH, is reported.

Purification and characterization of a salicylate hydroxylase involved in 1-hydroxy-2-naphthoic acid hydroxylation from the naphthalene and phenanthrene-degrading bacterial strain Pseudomonas putida BS202-P1.

1-Hydroxy-2-naphthoate is formed as an intermediate in the bacterial degradation of phenanthrene. A monooxygenase which catalyzed the oxidation of 1-hydroxy-2-naphthoate to 1,2-dihydroxynaphthalene was purified from the phenanthrene- and naphthalene-degrading Pseudomonas putida strain BS202-P1. The purified protein had a molecular weight of 45 kDa and required NAD(P)H and FAD as cofactors.

Xenobiotics in the environment: present and future strategies to obviate the problem of biological persistence.

Sustainable chemistry aims at an improved efficiency of using natural resources which are used to meet human needs for chemical products. Chemists in science and industry, have become aware of the importance to design environmentally benign chemicals. One aspect is the biological persistence and the present paper reviews work in this field focussing on the degradation of xenobiotics in the environment.

High-density sampling of a bacterial operon using mRNA differential display.

We have implemented a simplified high throughput approach to differential display in order to identify transcriptionally regulated genes in bacteria. In contrast with the few previous applications of differential display to prokaryotes, we use a large number of primers which allows for a high-density sampling of the mRNA population and the identification of many differentially amplified DNA fragments. From the overlap of these short sequences, long contiguous sequences that encode several genes can be assembled.

Genetic and biochemical characterization of an enantioselective amidase from Agrobacterium tumefaciens strain d3.

An enantioselective amidase was purified to homogeneity from Agrobacterium tumefaciens d3. The enzyme has a molecular mass of about 490000 Da and is composed of identical subunits with a molecular mass of about 63000 Da. The purified enzyme converted racemic 2-phenylpropionamide to the corresponding S-acid with an enantiomeric excess (ee) value >95% at almost 50% conversion of the racemic amide.

Campylobacter upsaliensis exerts a cytolethal distending toxin effect on HeLa cells and T lymphocytes.

Campylobacter upsaliensis is an emerging human enteropathogen. However, little is known about the pathogenesis of C. upsaliensis infection.

Ethene as an auxiliary substrate for the cooxidation of cis-1, 2-dichloroethene and vinyl chloride.

Cultures able to dechlorinate cis-1,2-dichloroethene (cDCE) were selected with ethene (3-20%, v/v) as the sole source of carbon and energy. One mixed culture (K20) could degrade cDCE (400 &mgr;mol l(-1)) or vinyl chloride (100 &mgr;mol l(-1)) in the presence of ethene ( View Article and Find Full Text PDF

Catalytic properties of the 3-chlorocatechol-oxidizing 2, 3-dihydroxybiphenyl 1,2-dioxygenase from Sphingomonas sp. strain BN6.

The 2,3-dihydroxybiphenyl dioxygenase from Sphingomonas sp. strain BN6 (BphC1-BN6) differs from most other extradiol dioxygenases by its ability to oxidize 3-chlorocatechol to 3-chloro-2-hydroxymuconic semialdehyde by a distal cleavage mechanism. The turnover of different substrates and the effects of various inhibitors on BphC1-BN6 were compared with those of another 2,3-dihydroxybiphenyl dioxygenase from the same strain (BphC2-BN6) as well as with those of the archetypical catechol 2,3-dioxygenase (C23O-mt2) encoded by the TOL plasmid.

Chemoselective nitro group reduction and reductive dechlorination initiate degradation of 2-chloro-5-nitrophenol by Ralstonia eutropha JMP134.

Ralstonia eutropha JMP134 utilizes 2-chloro-5-nitrophenol as a sole source of nitrogen, carbon, and energy. The initial steps for degradation of 2-chloro-5-nitrophenol are analogous to those of 3-nitrophenol degradation in R. eutropha JMP134.

Function of coenzyme F420 in aerobic catabolism of 2,4, 6-trinitrophenol and 2,4-dinitrophenol by Nocardioides simplex FJ2-1A.

2,4,6-Trinitrophenol (picric acid) and 2,4-dinitrophenol were readily biodegraded by the strain Nocardioides simplex FJ2-1A. Aerobic bacterial degradation of these pi-electron-deficient aromatic compounds is initiated by hydrogenation at the aromatic ring. A two-component enzyme system was identified which catalyzes hydride transfer to picric acid and 2,4-dinitrophenol.

3-Hydroxylaminophenol mutase from Ralstonia eutropha JMP134 catalyzes a Bamberger rearrangement.

3-Hydroxylaminophenol mutase from Ralstonia eutropha JMP134 is involved in the degradative pathway of 3-nitrophenol, in which it catalyzes the conversion of 3-hydroxylaminophenol to aminohydroquinone. To show that the reaction was really catalyzed by a single enzyme without the release of intermediates, the corresponding protein was purified to apparent homogeneity from an extract of cells grown on 3-nitrophenol as the nitrogen source and succinate as the carbon and energy source. 3-Hydroxylaminophenol mutase appears to be a relatively hydrophobic but soluble and colorless protein consisting of a single 62-kDa polypeptide.

Hydride-Meisenheimer complex formation and protonation as key reactions of 2,4,6-trinitrophenol biodegradation by Rhodococcus erythropolis.

Biodegradation of 2,4,6-trinitrophenol (picric acid) by Rhodococcus erythropolis HLPM-1 proceeds via initial hydrogenation of the aromatic ring system. Here we present evidence for the formation of a hydride-Meisenheimer complex (anionic sigma-complex) of picric acid and its protonated form under physiological conditions. These complexes are key intermediates of denitration and productive microbial degradation of picric acid.

Isolation of a bacterial strain with the ability to utilize the sulfonated azo compound 4-carboxy-4'-sulfoazobenzene as the sole source of carbon and energy.

A bacterial strain (strain S5) which grows aerobically with the sulfonated azo compound 4-carboxy-4'-sulfoazobenzene as the sole source of carbon and energy was isolated. This strain was obtained by continuous adaptation of "Hydrogenophaga palleronii" S1, which has the ability to grow aerobically with 4-aminobenzenesulfonate. Strain S5 probably cleaves 4-carboxy-4'-sulfoazobenzene reductively under aerobic conditions to 4-aminobenzoate and 4-aminobenzene-sulfonate, which are mineralized by previously established degradation pathways.

A new 4-nitrotoluene degradation pathway in a Mycobacterium strain.

Mycobacterium sp. strain HL 4-NT-1, isolated from a mixed soil sample from the Stuttgart area, utilized 4-nitrotoluene as the sole source of nitrogen, carbon, and energy. Under aerobic conditions, resting cells of the Mycobacterium strain metabolized 4-nitrotoluene with concomitant release of small amounts of ammonia; under anaerobic conditions, 4-nitrotoluene was completely converted to 6-amino-m-cresol.

Reduction of azo dyes by redox mediators originating in the naphthalenesulfonic acid degradation pathway of Sphingomonas sp. strain BN6.

The anaerobic reduction of azo dyes by Sphingomonas sp. strain BN6 was analyzed. Aerobic conversion of 2-naphthalenesulfonate (2NS) by cells of strain BN6 stimulated the subsequent anaerobic reduction of the sulfonated azo dye amaranth at least 10-fold.

Catabolism of 3-Nitrophenol by Ralstonia eutropha JMP 134.

Ralstonia eutropha JMP 134 utilizes 3-nitrophenol as the sole source of nitrogen, carbon, and energy. The entire catabolic pathway of 3-nitrophenol is chromosomally encoded. An initial NADPH-dependent reduction of 3-nitrophenol was found in cell extracts of strain JMP 134.