ISSN:
1432-072X
Keywords:
Key words Dichloromethane
;
Anaerobic
;
dehalogenation
;
Acetogenesis
;
Dehalobacterium
;
formicoaceticum
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract A strictly anaerobic, dichloromethane-utilizing bacterium was isolated from a previously described dichloromethane-fermenting, two-component mixed culture. In a mineral medium with vitamins, the organism converted 5 mM dichloromethane within 7 days to formate plus acetate in a molar ratio of 2:1 and to biomass and traces of pyruvate. Of 50 potential substrates and combinations of substrates tested, only dichloromethane supported growth. The organism had a DNA G+C content of 42.7 mol%. From its phylogenetic position deduced from 16S rDNA analysis and from its unique substrate range, we conclude that the organism represents a new genus and a new species within the phylum of the gram-positive bacteria for which we propose the name Dehalobacterium formicoaceticum. Cell extracts were found to contain carbon monoxide dehydrogenase, methylene tetrahydrofolate dehydrogenase, formyl tetrahydrofolate synthetase, and hydrogenase activities, whereas activities of methenyl tetrahydrofolate cyclohydrolase and methylene tetrahydrofolate reductase were not detectable. Activity for dehalogenation of dichloromethane was lost on preparation of cell extracts, but was maintained in cell suspensions. Oxygen and reagents that react with thiol groups caused irreversible inhibition, and propyl iodide caused reversible inhibition of dehalogenation. Our observations suggest: 1) conversion of dichloromethane to methylene tetrahydrofolate, which gives rise to both formate and the methyl group of acetate, or 2) conversion of two molecules of dichloromethane to methylene tetrahydrofolate (which is oxidized to formate) and parallel reductive dehalogenation of one dichloromethane to the methyl group of the corrinoid-protein involved in acetate formation.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s002030050362
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