Browsing by Author "Naumenko, E. A."

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Aerobic degradation of 2,4,6-trinitrotoluene by the yeast strain Geotrichum candidum AN-Z4
(2010-04) Ziganshin, Ayrat M.; Gerlach, Robin; Naumenko, E. A.; Naumova, R. P.
The yeast strain Geotrichum candidum AN-Z4 isolated from an anthropogenically polluted site was able to transform 2,4,6-trinitrotoluene (TNT) via the formation of unstable intermediate hydride Meisenheimer complexes with their subsequent destruction and accumulation of nitrite and nitrate ions as the end mineral forms of nitrogen. Aeration of the medium promoted more profound destruction of this xenobiotic by the strain G. candidum AN-Z4 than static conditions. The yeast strain was shown to produce citrate, succinate, and isocitrate, which sharply acidified the medium and influenced the TNT destruction. Two possible pathways of TNT biodegradation were confirmed experimentally: (1) via the destruction of the TNT-monohydride complex (3-Hâˆ’-TNT) and (2) via the destruction of one protonated TNT-dihydride complex (3,5-2Hâˆ’-TNT Â· H+). The strain G. candidum AN-Z4, due to its ability for TNT degradation, may be promising for bioremediation of TNT-contaminated soil and water.
Participation of oxygen in the bacterial transformation of 2,4,6-trinitrotoluene
(2008-04) Naumenko, E. A.; Naumov, A. V.; Suvorova, E. S.; Gerlach, Robin; Ziganshin, Ayrat M.; Lozhkin, A. P.; Silkin, N. I.; Naumova, R. P.
The exposure of Bacillus cereus ZS18 cell suspensions to 2,4,6-trinitrotoluene (TNT) in the absence of other oxidizable substrates increases oxygen uptake, exceeding the basal level of respiration of the bacterium 1.5- and 2-fold with 50 and 100 mg/liter of TNT, respectively. The interaction of both living and to less extent dead bacterial cells with TNT results in the accumulation of superoxide anion (O2-) in the extracellular medium, which was revealed by the EPR spectroscopy. The accumulation of O2- decreased by 50-70% in the presence of Cu,Zn-superoxide dismutase of animal origin. In the presence of living bacterial cells, the level of TNT decreased progressively, yielding hydroxylaminodinitrotoluenes together with O2-. In the presence of heat-killed cells, a moderate decrease in TNT was observed, and the appearance of O2- was not accompanied by the production of any detectable TNT metabolites. Chelating agents inhibited the transformation of TNT and decreased the formation of O2-. The demonstrated generation of O2- during the interaction of TNT with K4[Fe(CN)6] together with the observed effects of chelating agents suggest the participation of iron in the one-electron reduction of TNT and the functioning of an extracellular redox cycle with the involvement of molecular oxygen.