Biotransformation of 2,4,6-trinitrotoluene (TNT) by a Methanococcus sp. (strain B) isolated from a lake sediment

A mesophilic, irregular coccoid methanogen, which shows close resemblance to Methanococcus sp., was isolated from a sediment sample of St. Joseph Lake located in the University of Notre Dame campus. Formate or hydrogen plus carbon dioxide served as substrate for methanogenesis in a mineral salt medium. This organism was studied for its ability to metabolize 2,4,6-trinitrotoluene (TNT). The result showed that this isolate could transform 100 ppm of TNT within 40-60 days of incubation at 30 degrees C. The main intermediate produced was 2,4-diamino-6-nitrotoluene. The TNT transformation rates were higher in cells grown in hydrogen plus carbon dioxide than in cells grown in formate. The isolate did not use acetate and methanol as sole source of carbon and energy. The organism had an optimal pH range of 6.8-7.2. The optimal growth conditions for this isolate are described.