Anaerobic degradation of tetrachloromethane by Acetobacterium woodii: separation of dechlorinative activities in cell extracts and roles for vitamin B12 and other factors

Abstract

The transformations of 14CCl4 by whole cells of Acetobacterium woodii suspended in phosphate buffer containing reducing agents, and by the cobalt corrinoid aquocobalamin in the same solution, were compared. Each catalyst transformed 14CCl4 not only to reduced products (CHCl3 and CH2Cl2) but also to CO and CO2 as well as non-volatile products. The mass balance for radioactive carbon was complete in each case. Thus, the reactions of the pure cobalt corrinoid resemble the reactions in vivo. The proton in CHCl3, formed from CCl4 by A. woodii, was derived from water. Extracts of A. woodii were fractionated into large and small molecules, and each of the two fractions was separated chromatographically. Fractions of proteins demonstrated poor correlation between content of the corrinoid vitamin B12 and rates of transformation of CCl4. The correlation was somewhat improved if the fractions were autoclaved, but dechlorination in the absence of vitamin B12 was observed. Separation of the small molecules yielded only one fraction containing vitamin B12, and this fraction catalyzed dechlorination, whereas several other fractions were able to dechlorinate CCl4 in the absence of vitamin B12. We presume there to be unrecognized dechlorinative factors in anaerobic bacteria.