ENHANCED DECHLORINATION OF CARBON-TETRACHLORIDE AND CHLOROFORM IN THEPRESENCE OF ELEMENTAL IRON AND METHANOSARCINA-BARKERI, METHANOSARCINA-THERMOPHILA, OR METHANOSAETA-CONCILLII

Previous experiments in our laboratory have demonstrated that the rate and extent of carbon tetrachloride (CT) and chloroform (CF) dechlorin ation were enhanced when a methanogenic enrichment culture and iron (F eO) were incubated together. Batch experiments with three pure culture s of methanogens, Methanosarcina barkeri, Methanosarcina thermophila, acid Methanosaeta concillii were performed to determine how this enhan ced transformation occurred. When hydrogen (H-2) was added as an elect ron donor, degradation of CT for all organisms and CF for M. thermophi la was more rapid. HE was produced from the oxidation of iron, which t herefore served as an H-2 source for the organisms, enhancing the tran sformation of CT and CF. Experiments with IM. thermophila and M. conci llii, which could not grow on H-2-CO2 under the conditions tested, sho wed that H-2 could serve as an electron donor for dechlorination of CT and CF with these organisms as well. Experiments with supernatants fr om M. thermophila grown with and without iron indicated the presence o f an excreted biomolecule active in the enhanced transformation of CT and CF.