Comparison of DNA binding between the carcinogen 2,6-dinitrotoluene and its noncarcinogenic analog 2,6-diaminotoluene

Biotransformation of nitro aromatic amines in artificial alkaline habitat by pseudomonas DL17

Nitro-aromatics are listed in carcinogenic, teratogenic, and mutagenic compounds list. p-nitro-aniline is one of them used as a precursor of various chemical compounds in many industries like dyes, drugs, paints and several others. These are mostly given out as an effluent in rivers, lakes or open passage of land which exert several hazards to living creatures and environment. Some of the organic compounds are stable in alkaline condition and persist longer in environment. Very few reports are elaborating bio-remediation in alkaline condition using different hydrocarbons. This study was planned to elaborate mechanism of detoxification and searching the potential of decontamination of p-nitro-aniline in alkaline condition by experimental microbial strain. The bacterial strain pseudomonas DL17 was isolated from alkaline Lake Lonar, Buldana, (MS.) India; and employed in this experiment considering its indigenous property to tolerate the alkaline pH. It also showed resistance to p-nitro-aniline with its raising concentrations on testing after adaptation. The experimental microbial stain showed 100% biodegradation of (500 mg/L) p-nitro-aniline within 48h. On shaking incubator with 110 rpm and at 32 °C optimum temperature. The centrifugate obtained after spinning at 10,000 g by cold centrifuge was used for solvent extraction. Generally, ethyl acetate or DCM was used for solvent extraction. The estimation of residual remains of p-nitro aniline by 6h. intervals was carried after removal of flasks from shaking incubator and centrifugation. At the optimum temperature and pH experiments were carried after knowing the resistance to experimental contaminant range (100–400 mg/L) of p-nitro aniline one month and further extended to 500 mg/L for 15days more.

The residual metabolites were purified by column chromatography and various spectrometric studies such as UV-Vis spectroscopy, HNMR, FTIR and GCMS revealed that p-Phenylenediamine, acetanilide, aniline, acetaminophen, catechol, p-bezoquinone, cis-cis muconate as a metabolites. On the basis of the metabolites isolated and characterized by different spectroscopic studies the bio-catalytic mechanism was deduced. The induced enzymes such as nitroreductase, catalase, peroxidase, acetanilide hydroxylase, super oxide dismutase, catechol 1, 2 dioxygenase, catechol 2, 3 dioxygenase has commercial importance in biochemical industries. Induction of such biotransformation enzymes and consumption of p-nitro aniline concentration in experiments makes sure that this microbial strain pseudomonas DL17 can be employed for decontamination of nitro aniline polluted sites as well as isolation of such metabolites characterized and enzymes studied.

Biomonitoring of arylamines and nitroarenes

Arylamines and nitroarenes are very important intermediates in the industrial manufacture of dyes, pesticides and plastics, and are significant environmental pollutants. The metabolic steps of N-oxidation and nitroreduction to yield N-hydroxyarylamines are crucial for the toxic properties of arylamines and nitroarenes. Nitroarenes are reduced by microorganisms in the gut or by nitroreductases and aldehyde dehydrogenase in hepatocytes to nitrosoarenes and N-hydroxyarylamines. N-Hydroxyarylamines can be further metabolized to N-sulphonyloxyarylamines, N-acetoxyarylamines or N-hydroxyarylamine N-glucuronide. These highly reactive intermediates are responsible for the genotoxic and cytotoxic effects of this class of compounds. N-Hydroxyarylamines can form adducts with DNA, tissue proteins, and the blood proteins albumin and haemoglobin in a dose-dependent manner. DNA and protein adducts have been used to biomonitor humans exposed to such compounds. All these steps are dependent on enzymes, which are present in polymorphic forms. This article reviews the metabolism of arylamines and nitroarenes and the biomonitoring studies performed in animals and humans exposed to these substances.

Microbial remediation of NTO in aqueous industrial wastes

The bioremediation of aqueous wastes containing 5-nitro-1,2,4-triazol-3-one (NTO) was investigated. The microorganism used is a Bacillus licheniformis strain, isolated from the contaminated solutions by enrichment techniques. The biodegradation was carried out in the waste (15 g l-1 NTO) and proceeded through the nitroreduction of NTO, followed by the ring cleavage of the formed primary amine 5-amino-1,2,4-triazol-3-one (ATO). Both steps were optimized and according to the optimal conditions, the nitroreduction of NTO is total in 24 h, while the degradation of ATO requires 2 weeks of incubation. The end products of the biodegradation were carbon dioxide (40%), urea and a polar compound, assumed to be hydroxyurea. A mechanism of ATO ring cleavage was postulated in the light of experimental data, and led us to propose an overall degradation sequence for NTO.

Spectrum of spontaneous and 2,4,6-trinitrotoluene (TNT)-induced mutations in Salmonella typhimurium strains with different nitroreductase and O-acetyltransferase activities

Spontaneous and 2,4,6-trinitrotoluene (TNT)-induced mutation spectra were determined at the hisD3052 allele of Salmonella typhimurium strains TA98, YG1021 (nitroreductase-overproducing) and YG1024 (O-acetyltransferase-overproducing). In TA98, 55% (11/20) of the spontaneous reversions and 95% (19/20) of reversions in TNT-treated plates were deletions of two bases at the same site (-2 hotspot deletions), whereas the respective figures were 65% (13/20) and 80% (16/20) in YG1021, and 75% (15/20) and 95% (19/20) in YG1024. Other mutations observed in the TNT treatment were complex frameshifts consisting of either a -2 hotspot deletion and a base substitution, or a +1 addition and base substitution at the stop codon. In addition, different kinds of deletions were recovered in the spontaneous spectra. The elevated enzymatic activities of strains, YG1021 and YG1024, resulting in enhanced mutagenicity of TNT, did not seem to have an effect on the spectrum of TNT-induced mutations. However, the YG strains, which also have a higher spontaneous revertant yield than the parental strain TA98, seemed to differ from TA98 in their spontaneous spectra. The increase consisted of revertants containing the -2 hotspot deletion, possibly indicating elevated activation of exogenous or endogenous premutagens by the higher enzyme activities of the YG strains.