Participation of oxygen in the bacterial transformation of 2,4,6-trinitrotoluene

Abstract

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 ($O_2^{\dot ---}$ ) in the extracellular medium, which was revealed by the EPR spectroscopy. The accumulation of $O_2^{\dot ---}$ 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 $O_2^{\dot ---}$ . In the presence of heat-killed cells, a moderate decrease in TNT was observed, and the appearance of $O_2^{\dot ---}$ was not accompanied by the production of any detectable TNT metabolites. Chelating agents inhibited the transformation of TNT and decreased the formation of $O_2^{\dot ---}$ . The demonstrated generation of $O_2^{\dot ---}$ 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.