Biodegradation of Nitrated Munition Compounds and Herbicides by Obligately Anaerobic Bacteria

Abstract

Research performed during the 1970s (15, 18) generally indicated that complete biomineralization of 2,4,6-trinitrotoluene (TNT) and similar highly nitrated compounds did not occur. Biological reductions (R-NO₂ → R-NO → R-NHOH → R-NH₂) and polymerization reactions appeared to occur, but actual degradation of aromatic nuclei was not observed. However, this work involved studies of aerobic systems such as activated sludge and thermophilic composts, and pure cultures of aerobic fungi and bacteria such as pseudomonads. Pure cultures of some anaerobic bacteria such as Veillonella alcalescens (35) were examined, with similar results. Boopathy and Kulpa (2) recently isolated a Desulfovibrio that used TNT as a sole source of nitrogen, producing toluene as an end product. A Pseudomonas that produced dinitrotoluene, mononitrotoluene, and toluene from TNT, perhaps by hydride additions, was isolated by Duque et al. (10). These are still incomplete degradations of the parent molecule. Since the Desulfovibrio strain required obligately anaerobic conditions to produce toluene from TNT, and the Pseudomonas did so aerobically, the TNT transformation process may be mechanistically different in the two microorganisms. This should be a fruitful area for future research.