Transformations of TNT and related aminotoluenes in groundwater aquifer slurries under different electron-accepting conditions

Krumholz, Lee R.; Li, J; Clarkson, W. W.; Wilber, Gregory G.; Suflita, Joseph M.

doi:10.1038/sj.jim.2900317

Cited by 32 publications

(30 citation statements)

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“…Williams et al (41) observed significant TNT disappearance from contaminated soil in both thermophilic and mesophilic composting conditions. A similar study on TNT remediation has also been reported for groundwater aquifer slurries by Kromholt et al (23). If physiological conditions optimal for enzymatic reactions favoring TNT reduction can be maintained, the remediation would be more effective.…”

Section: Discussionsupporting

confidence: 64%

2,4,6-Trinitrotoluene Reduction by an Fe-Only Hydrogenase in Clostridium acetobutylicum

Watrous¹,

Clark

Kutty

et al. 2003

Appl Environ Microbiol

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The role of hydrogenase on the reduction of 2,4,6-trinitrotoluene (TNT) in Clostridium acetobutylicum was evaluated. An Fe-only hydrogenase was isolated and identified by using TNT reduction activity as the selection basis. The formation of hydroxylamino intermediates by the purified enzyme corresponded to expected products for this reaction, and saturation kinetics were determined with a K m of 152 M. Comparisons between the wild type and a mutant strain lacking the region encoding an alternative Fe-Ni hydrogenase determined that Fe-Ni hydrogenase activity did not significantly contribute to TNT reduction. Hydrogenase expression levels were altered in various strains, allowing study of the role of the enzyme in TNT reduction rates. The level of hydrogenase activity in a cell system correlated (R 2 ‫؍‬ 0.89) with the organism's ability to reduce TNT. A strain that overexpressed the hydrogenase activity resulted in maintained TNT reduction during late growth phases, which it is not typically observed in wild type strains. Strains exhibiting underexpression of hydrogenase produced slower TNT rates of reduction correlating with the determined level of expression. The isolated Fe-only hydrogenase is the primary catalyst for reducing TNT nitro substituents to the corresponding hydroxylamines in C. acetobutylicum in whole-cell systems. A mechanism for the reaction is proposed. Due to the prevalence of hydrogenase in soil microbes, this research may enhance the understanding of nitroaromatic compound transformation by common microbial communities.

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Section: Discussionsupporting

confidence: 64%

2,4,6-Trinitrotoluene Reduction by an Fe-Only Hydrogenase in Clostridium acetobutylicum

Watrous¹,

Clark

Kutty

et al. 2003

Appl Environ Microbiol

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“…Nitrate respiraton conditions gave the best degradation rate with a consortium of soil bacteria (33), whereas methanogenesis seemed to be optimal with slurries of aquifer sediment (135).…”

Section: Vol 65 2001 Metabolism Of Nitroaromatic Compounds 341mentioning

confidence: 99%

Biological Degradation of 2,4,6-Trinitrotoluene

Esteve‐Núñez

Caballero

Ramos

2001

Microbiol Mol Biol Rev

417

287

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Nitroaromatic compounds are xenobiotics that have found multiple applications in the synthesis of foams, pharmaceuticals, pesticides, and explosives. These compounds are toxic and recalcitrant and are degraded relatively slowly in the environment by microorganisms. 2,4,6-Trinitrotoluene (TNT) is the most widely used nitroaromatic compound. Certain strains of Pseudomonas and fungi can use TNT as a nitrogen source through the removal of nitrogen as nitrite from TNT under aerobic conditions and the further reduction of the released nitrite to ammonium, which is incorporated into carbon skeletons. Phanerochaete chrysosporium and other fungi mineralize TNT under ligninolytic conditions by converting it into reduced TNT intermediates, which are excreted to the external milieu, where they are substrates for ligninolytic enzymes. Most if not all aerobic microorganisms reduce TNT to the corresponding amino derivatives via the formation of nitroso and hydroxylamine intermediates. Condensation of the latter compounds yields highly recalcitrant azoxytetranitrotoluenes. Anaerobic microorganisms can also degrade TNT through different pathways. One pathway, found in Desulfovibrio and Clostridium, involves reduction of TNT to triaminotoluene; subsequent steps are still not known. Some Clostridium species may reduce TNT to hydroxylaminodinitrotoluenes, which are then further metabolized. Another pathway has been described in Pseudomonas sp. strain JLR11 and involves nitrite release and further reduction to ammonium, with almost 85% of the N-TNT incorporated as organic N in the cells. It was recently reported that in this strain TNT can serve as a final electron acceptor in respiratory chains and that the reduction of TNT is coupled to ATP synthesis. In this review we also discuss a number of biotechnological applications of bacteria and fungi, including slurry reactors, composting, and land farming, to remove TNT from polluted soils. These treatments have been designed to achieve mineralization or reduction of TNT and immobilization of its amino derivatives on humic material. These approaches are highly efficient in removing TNT, and increasing amounts of research into the potential usefulness of phytoremediation, rhizophytoremediation, and transgenic plants with bacterial genes for TNT removal are being done

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“…Numerous studies examining the reduction of TNT by intact bacterial cells report either transformation to ADNTs without the accumulation of any intermediates (6,7,24,27,35,42,46,49) or the transient accumulation of HADNTs with subsequent transformation to ADNTs (13, 15, 28, 38, 58, 59). However, experiments using single enzymes to transform TNT and other nitroarenes produce hydroxylaminoarenes exclusively, without any production of aminoarenes (22,43,45,50,54).…”

Section: Discussionmentioning

confidence: 99%

“…(39), Vellonella spp. (40), nitrate-reducing bacteria (6,35), Pseudomonas spp. (42), Enterobacter cloacae (23), and Salmonella enterica serovar Typhimurium (60).…”

mentioning

confidence: 99%

NAD(P)H:Flavin Mononucleotide Oxidoreductase Inactivation during 2,4,6-Trinitrotoluene Reduction

Riefler

Smets

2002

Appl Environ Microbiol

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Bacteria readily transform 2,4,6-trinitrotoluene (TNT), a contaminant frequently found at military bases and munitions production facilities, by reduction of the nitro group substituents. In this work, the kinetics of nitroreduction were investigated by using a model nitroreductase, NAD(P)H:flavin mononucleotide (FMN) oxidoreductase. Under mediation by NAD(P)H:FMN oxidoreductase, TNT rapidly reacted with NADH to form 2-hydroxylamino-4,6-dinitrotoluene and 4-hydroxylamino-2,6-dinitrotoluene, whereas 2-amino-4,6-dinitrotoluene and 4-amino-2,6-dinitrotoluene were not produced. Progressive loss of activity was observed during TNT reduction, indicating inactivation of the enzyme during transformation. It is likely that a nitrosodinitrotoluene intermediate reacted with the NAD(P)H:FMN oxidoreductase, leading to enzyme inactivation. A half-maximum constant with respect to NADH, K N , of 394 M was measured, indicating possible NADH limitation under typical cellular conditions. A mathematical model that describes the inactivation process and NADH limitation provided a good fit to TNT reduction profiles. This work represents the first step in developing a comprehensive enzyme level understanding of nitroarene biotransformation.2,4,6-Trinitrotoluene (TNT), a widely used explosive, is a contaminant frequently found at military bases and munitions production facilities. In addition to its explosion hazard, TNT is a suspected mutagen (56). Extensive research is under way to determine methods for remediation of soil and groundwater contaminated with this pollutant. Bacteria under both aerobic and anaerobic conditions commonly reduce TNT. The nitrogen atom in a nitro group retains a net positive charge and consequently is a strong electrophile and susceptible to reduction. Nitro groups are typically reduced by the sequential addition of three electron pairs, producing a nitroso group, a hydroxylamino group, and finally an amino group (40, 55). Nitroso intermediates are extremely reactive and account for much of the toxicity associated with nitroarenes (56). Through successive reductions of the nitro groups, microorganisms sequentially transform TNT to aminodinitrotoluenes (ADNTs), diaminonitrotoluenes, and triaminotoluene (13,24,46,49,55). As electron-deficient nitrogen atoms are reduced, the molecule becomes less susceptible to reduction and reaction rates decrease, i.e., TNT is reduced faster than ADNTs and ADNTs are reduced faster than diaminonitrotoluenes (13,33,40,42,46). To date, there is no conclusive evidence that mineralization of TNT via a triaminotoluene pathway occurs.Products other than amino compounds have been identified during bacterial nitroarene reduction. Numerous studies have reported the accumulation of hydroxylamino compounds (15,33,46,48), and hydroxylamino and nitroso intermediates may abiotically condense to azoxy dimers that persist (24,27,28,40). TNT is also susceptible to aerobic hydrogenation of the aromatic ring. Several research groups have reported the formation of a Meisenheimer complex and a di...

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Transformations of TNT and related aminotoluenes in groundwater aquifer slurries under different electron-accepting conditions

Cited by 32 publications

References 1 publication

2,4,6-Trinitrotoluene Reduction by an Fe-Only Hydrogenase in Clostridium acetobutylicum

2,4,6-Trinitrotoluene Reduction by an Fe-Only Hydrogenase in Clostridium acetobutylicum

Biological Degradation of 2,4,6-Trinitrotoluene

NAD(P)H:Flavin Mononucleotide Oxidoreductase Inactivation during 2,4,6-Trinitrotoluene Reduction

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