文摘
The ability of a metal-reducing bacterium to microbiallyreduce vitamin B12 was determined to expand ourunderstanding of the role vitamin B12 plays in thetransformationof halogenated compounds in microbial systems. Thesubsequent transformation of chlorinated methanescatalyzed by this microbially-reduced vitamin B12 wasthenevaluated. When incubated in the presence ofShewanellaalga strain BrY and an electron donor, the microbialreductionof vitamin B12a to B12r was observed as a shiftin the vitaminB12 spectrum. In treatments containing vitaminB12 and anelectron donor but without BrY, the predominant specieswas vitamin B12a. The introduction of BrY into thesystemresulted in the production of vitamin B12r. Thetransformationof carbon tetrachloride (CT), chloroform (CF), anddichloromethane (DCM) was examined in batch systemscontaining vitamin B12, Shewanella alga strainBrY, and anelectron donor. Transformation of both CT and CF wasobserved, while no significant change in the DCMconcentration was detected. Carbon monoxide was the majorproductof CT transformation. No significant transformation ofCTor CF was detected when vitamin B12 was omittedfromthe system. This work demonstrates that ametal-reducingbacterium, with no apparent ability to transform CT or CFdirectly, mediates the reduction of vitamin B12, whichinturn catalyzes the transformation of CT.