NOVEL METABOLITE OF TRICHLOROETHYLENE IN A METHANOTROPHIC BACTERIUM, METHYLOCYSTIS SP M, AND HYPOTHETICAL DEGRADATION PATHWAY

Previously, a new type II methanotrophic bacterium, Methylocystis sp. M (strain M), was isolated in our laboratory [H. Uchiyama et al., Agric. Biol. Chem., 53, 2903-2907 (1989)]. In this paper, metabolites resulting from the degradation of trichloroethylene (TCE) by strain M were studied with gas chromatography-mass spectrometry. Trichloroacetic acid, dichloroacetic acid, and a small amount of 2,2,2-trichloroethanol were detected in the water-soluble fraction of the reaction mixture. These results suggest that the conversion of TCE to trichloroacetaldehyde via a Cl-shift reaction, followed by the formation of trichloroacetic acid and 2,2,2-trichloroethanol, as well as a spontaneous breakdown of TCE oxide, with subsequent formation of dichloroacetic acid, etc., is involved in the TCE degradation pathway of the methanotrophic bacterium.