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Biotransformation and partial mineralization of the explosive 2,4,6-trinitrotoluene (TNT) by rhizobia
Mohamed Labidi, Darakhshan Ahmad, Annamaria Halasz, and Jalal Hawari

Abstract: Three strains, T10, B5, and M8, each belonging to a different species of the family Rhizobiaceae and isolated from atrazine-contaminated soils, were tested for their ability to transform 2,4,6-trinitrotoluene (TNT) (50 µg·mL–1) in liquid cultures using glucose as the C-source. All three strains were able to transform TNT to hydroxylaminodinitrotoluenes (2-HADNT, 4-HADNT), aminodinitrotoluenes (2-ADNT, 4-ADNT), and diaminonitrotoluene (2,4-DANT). The transformation was significantly faster in the presence of glutamate. Furthermore, the major metabolites that accumulated in cultures were 2-ADNT with glucose, and 4-ADNT with glutamate plus glucose. Rhizobium trifolii T10 was also tested for its ability to transform high levels of TNT (~350 µg·mL–1) in a soil slurry. Almost 60% of the TNT was transformed within 2 days in bioaugmented soil slurries, and up to 90% when cultures were supplemented with glucose and glutamate. However, mineralization was minimal in all cases, less than 2% in 78 days. This is the first report on the degradation of TNT by rhizobial strains, and our findings suggest that rhizobia have the potential to play an important role in the safe decontamination of soils and sites contaminated with TNT if bioaugmentation with rhizobia is shown to have no ecotoxicological consequence. Key words: Rhizobium, 2,4,6-trinitrotoluene (TNT), biotransformation. Résumé : Les trois souches T10, B5 et M8, appartenant chacune à différents groupes de la famille Rhizobiaceae et Labidi et al. isolées à partir de sols contaminés à l’atrazine, ont été testés pour leur habileté à transformer le 2,4,6-trinitrotoluène (TNT) (50 µg·mL–1) dans des cultures en milieu liquide utilisant le glucose comme source de carbone. Toutes les souches ont été capable de transformer le TNT en