Participation of Oxygen in the Bacterial Transformation of 2,4,6-Trinitrotoluene

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E. A. Naumenko¹, A. V. Naumov², E. S. Suvorova², R. Gerlach², A. M. Ziganshin¹, A. P. Lozhkin¹, N. I. Silkin¹, and R. P. Naumova^1*

¹Kazan State University, ul. Kremlyovskaya 18, 420008 Kazan, Russia; E-mail: r.p.naumova@gmail.com

²Montana State University, Bozeman, MT 59717, USA

^* To whom correspondence should be addressed.

Received June 20, 2007; Revision received July 9, 2007

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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.

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KEY WORDS: 2,4,6-trinitrotoluene, aerobic transformation, superoxide anion

DOI: 10.1134/S0006297908040123

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