Type I nitroreductases in soil enterobacteria reduce TNT (2,4,6-trinitrotoluene) and RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) (original) (raw)
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Degradation of 2,4,6-Trinitrotoluene (TNT)by Soil Bacteria Isolated From TNT Contaminated Soil
Twenty bacterial strains isolated from TNT contaminated soil. Among those strains only five were highly efficient for their abilities to grow in basal salt medium containing TNT as sole nitrogen source. From these isolates only two strains were more potent for TNT degradation in aerobic condition. These strains were identified as Clavibacter agropyi (Corynebacterium) (R.L1) and Sphingomonas sanguinis (R.L2).These strains had shown good growth with disappearance of TNT and concomitantly release of nitrite over the period of incubation time. TNT and its metabolites were analyzed by gas chromatography (GC) and results were confirmed and identified by gas chromatography/Mass spectrometer (GC/MS). The biodegradation of TNT was initially similar regardless of the microorganism. Generally, the initial degradation involved the reduction or removal of the nitro substitute giving way to an amino derivative or free nitrite. The identified amino derivatives were, P-toluidine,3,5-dinitro and Benzenamine,2-methyl-3,5-dinitro.which are known as 2amino-4,6-dinitrotoluene(2-ADNT) and 4-amino-2,6-dinitrotoluene (4-ADNT) respectively. Nitrite liberation was consistently found coincided with TNT disappearance from the medium. The disappearance of TNT was completely within 7days by the two isolates and/or their mixture. This is encouraging, and may indicate their potential in bioremediation of TNT contaminated soils. This is the first report on Clavibacterium agropyri (Corynebacterium) and Sphingomonas sanguinis for degradation of TNT with nitrite release into the medium.
Applied and Environmental Microbiology, 1994
Three species of the family Enterobacteriaceae that biochemically reduced hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) were isolated from nitramine explosive-contaminated soil. Two isolates, identified as Morganella morganii and Providencia rettgeri, completely transformed both RDX and the nitroso-RDX reduction intermediates. The third isolate, identified as Citrobacter freundii, partially transformed RDX and generated high concentrations of nitroso-RDX intermediates. All three isolates produced 14CO2 from labeled RDX under O2-depleted culture conditions. While all three isolates transformed HMX, only M. morganii transformed HMX in the presence of RDX.
Biodegradation of nitro-explosives
2003
Environmental contamination by nitro compounds is associated principally with the explosives industry. However, global production and use of explosives is unavoidable. The presently widely used nitro-explosives are TNT (Trinitrotoluene), RDX (Royal Demolition Explosive) and HMX (High Melting Explosive). Nevertheless, the problems of these nitro-explosives are almost parallel due to their similarities of production processes, abundance of nitro-explosives and resembling chemical structures. The nitro-explosives per se as well as their environmental transformation products are toxic, showing symptoms as methaemoglobinaemia, kidney trouble, jaundice etc. Hence their removal/degradation from soil/water is essential. Aerobic and anaerobic degradation of TNT and RDX have been reported, while for HMX anaerobic or anoxic degradation have been described in many studies. A multisystem involvement using plants in remediation is gaining importance. Thus the information about degradation of nitr...
Biotechnology Letters, 2020
Objective To evaluate the ability of Janibacter cremeus a soil bacterium isolated from explosive contaminated site in degradation of hexahydro-1,3,5trinitro-1,3,5-triazine (RDX) and to study enzyme responsible for degradation. Results The isolate exhibited 88% degradation of RDX in 30 days of incubation. The biodegradation process followed the first order kinetics. The half-life of RDX was calculated to be 11.088 days. The RDX degradation process was complemented by concomitant release of nitrite ions with 0.78 mol of nitrite released per mole of RDX. The metabolites; Trinitroso-RDX, diamino-RDX, trimino-RDX, bis-(hydroxymethyl) nitramine and methylenedintramine derivative, viz, methylene-N-(hydroxy-methyl)hydroxylamine-N-(hydroxymethyl) nitroamine corresponding to the molecular weights 174, 162, 132, 122 and 167 Da respectively were also detected. Nitroreductase enzyme was found to be responsible for RDX degradation. Conclusion J. cremeus could degrade RDX as sole source of nitrogen, via three different pathways wherein, Nitroreductase enzyme was found to play a major role. The efficient degradation of RDX makes J. cremeus suitable in treatment of contaminated water and soil at field scale levels. Keywords Bioremediation Á Degradation pathway Á Explosives Á Nitroreductase enzyme List of symbols ln Natural logarithm k Rate constant Electronic supplementary material The online version of this article (
PnrA, a new nitroreductase-family enzyme in the TNT-degrading strain Pseudomonas putida JLR11
Environmental Microbiology, 2005
Nitroreductases are a group of proteins that catalyse pyridine nucleotide-dependent reduction of nitroaromatics compounds, showing significant human health and environmental implications. In this study we have identified the nitroreductase-family enzymes PnrA and PnrB from the TNT-degrading strain Pseudomonas putida. The enzyme encoded by the pnrA gene was expressed in Escherichia coli , purified to homogeneity and shown to be a flavoprotein that used 2 mol of NADPH to reduce 1 mol of 2,4,6-trinitrotoluene (TNT) to 4-hydroxylamine-2,6dinitrotoluene, using a ping-pong bi-bi mechanism. The PnrA enzyme also recognized as substrates as a number of other nitroaromatic compounds, i.e. 2,4dinitrotoluene, 3-nitrotoluene, 3-and 4-nitrobenzoate, 3,5-dinitrobenzamide and 3,5-dinitroaniline expanding the substrates profile from previously described nitroreductases. However, TNT resulted to be the most efficient substrate examined according to the V max /K m parameter. Expression analysis of pnrA-and pnrB-mRNA isolated from cells growing on different nitrogen sources suggested that expression of both genes was constitutive and that its level of expression was relatively constant regardless of the growth substrate. This is in agreement with enzyme-specific activity determined with cells growing with different N-sources.
Bioresource Technology, 1994
Four Pseudomonas spp. were isolated from a soil consortium enriched from soil contaminated with 2,4,6-trinitrotoluene (TNT). All four species extensively transformed TNT. The rate of transformation varied among species. In isolate 4, 100% of TNT (100 ppm) was transformed in 4 days. The TNT transformation was achieved by the four isolates through a co-metabolic process with a succinate co-substrate. The four isolates produced NOj from TNT. The maximum NO;-production, observed for isolate 1, was equal to 30% of the NO; available from the nitro groups of TNT. For other isolates the NO;_ production varied from 10 to 16%. The radiolabeling studies showed signs of ring cleavage. Isolate 3 used 13%
Microbial Transformation of Nitroaromatics in Surface Soils and Aquifer Materials
Applied and Environmental Microbiology, 1994
Microorganisms indigenous to surface soils and aquifer materials collected at a munitions-contaminated site transformed 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (2,4-DNT), and 2,6-dinitrotoluene (2,6-DNT) to amino-nitro intermediates within 20 to 70 days. Carbon mineralization studies with both unlabeled (TNT, 2,4-DNT, and 2,6-DNT) and radiolabeled ([ 14 C]TNT) substrates indicated that a significant fraction of these source compounds was degraded to CO 2 .
Environmental Science & Technology, 1998
The explosive 2,4,6-trinitrotoluene (TNT), found as a major contaminant at armament plants from the two world wars, is reduced by a variety of microorganisms when electron donors such as glucose are added. This study shows that the cometabolic reduction of TNT to 2,4,6-triaminotoluene by an undefined anaerobic consortium increased considerably with increasing TNT concentrations and decreased with decreasing concentrations and feeding rates of glucose. The interactions of TNT and its reduction products with montmorillonitic clay and humic acids were investigated in abiotic adsorption experiments and during the microbial reduction of TNT. The results indicate that reduction products of TNT particularly hydroxylaminodinitrotoluenes and 2,4,6-triaminotoluene bind irreversibly to soil components, which would prevent or prolong mineralization of the contaminants. Irreversible binding also hinders a further spread of the contaminants through soil or leaching into the groundwater.
2022
2,4,6-Trinitrotoluene (TNT), a nitro-aromatic explosive commonly used for defence and several non-violent applications is contributing to serious environmental pollution problems including human health. The current study investigated the remediation potential of a native soil isolate i.e., Planomicrobium flavidum (strain S5-TSA-19) against TNT. At a TNT concentration of 120 mg/L with a specified environment, the isolate remained incubated for 30 days in a minimal salt medium (MSM). Regular growth of the isolate, the concentration of TNT, nitrate, nitrite and ammonium ion were evaluated at a particular time during the experiment. Within 168 hours (i.e., 7 days) of incubation, P. flavidum co-metabolically degraded 100% TNT. The biodegradation procedure succeeded the first order kinetics mechanism. Formation of additional metabolites like 2,4-dinitrotoluene (DNT), 2,4-diamino-6-nitrotoluene (2-DANT) and 2-amino-4,6-dinitrotoluene (2-ADNT), were also witnessed. TNT seems to be non-toxic...