Isolation and characterization of a sulfate-reducing bacterium that removed TNT (2,4,6-trinitrotoluene) under sulfate- and nitrate-reducing conditions

Abstract

A sulfate-reducing bacterium isolated from a creek sediment and capable of metabolizing TNT (2,4,6-trinitrotoluene) using sulfate and nitrate as electron acceptors was tentatively characterized as Desulfovibrio desulfuricans strain A. The isolate was unable to use TNT as the sole source of carbon. TNT degradation was accomplished by a co-metabolic process using pyruvate as the main substrate. Two different metabolic steps were employed by this isolate under different electron-accepting conditions. Under sulfate-reducing conditions, TNT was reduced to 4-amino-2,6-dinitrotoluene, 2-amino-4,6-dinitrotoluene and 2,4-diamino-6-nitrotoluene. In contrast, under nitrate-reducing conditions, these amino compounds were not produced, instead, butyric acid was identified as the major metabolite of TNT metabolism. This organism also used a wide variety of other carbon sources, including ethanol, lactate, succinate, formate and malate. The isolate contained the electron-carrier desulfoviridin and used sulfate, nitrate, and thiosulfate as electron acceptors. The isolate had an optimal temperature of 25°C and an optimal pH of 6.8 and used ammonium chloride, nitrate and glutamate as nitrogen sources. The characteristic features of the sulfate-reducing bacterium closely resembled those of Desulfovibrio desulfuricans.