Dechlorination of chloroform by methanosarcina strains.

Dehalogenation of carbon tetrachloride, chloroform, and bromoform in pure cultures of Methanosarcina sp. strain DCM and Methanosarcina mazei S6 was demonstrated. The initial dechlorination product of chloroform was methylene chloride (dichloromethane), which accumulated transiently to about 70% of the added chloroform; trace amounts of chloromethane were also detected. The amount of chloroform dechlorinated per mole of methane produced was approximately 10 times greater than the ratio observed previously for tetrachloroethene dechlorination by these strains. The production of CO(2) from [C]chloroform and the absence of CH(4) imply that processes in addition to reductive dechlorination operate.