Transformat ion of tetra- and t r ichloromethane to CO 2 by anaerobic bacteria is a non-enzymic process

Degradation of tetrachloromethane was examined in the three strictly anaerobic bacteria, Acetobacterium woodii. Desulfobacterium autotrophicum and Methanobacterium thermoauwtrophicum. When incubated under anaerobic conditions in reduced buffer, suspensions of each organism degraded CCI4 by both reductive and substitutive mechanisms. The products formed included less-highly chlorinated methanes and CO 2. Cell-free extracts of A. woodii degraded tetrachloromethane in a manner similar to that in whole cells but at a lower rate (63 vs. 110/~kat/kg of protein). When M. thermoautotrophicum or A. woodii was autoclaved, reductive dechlorination was partly abolished, whereas substitutive dechlorination was retained. Trichloromethane was oxidized to CO 2 by both native and autoclaved cells of A. woodii. Halomethanes are thus degraded anaerobically by reductive, substitutive and oxidative mechanisms.