Cobalt limitation of growth and mercury methylation in sulfate-reducing bacteria.

Sulfate-reducing bacteria (SRB) have been identified as the primary organisms responsible for monomethylmercury (MeHg) production in aquatic environments, but little is known of the physiologyand biochemistry of mercury(Hg) methylation. Corrinoid compounds have been implicated in enzymatic Hg methylation, although recent experiments with a vitamin B12 inhibitor indicated that incomplete-oxidizing SRB likely do not use a corrinoid-enzyme for Hg methylation, whereas experiments with complete-oxidizing SRB were inconclusive due to overall growth limitation. Here we explore the role of corrinoid-containing methyltransferases, which contain a cobalt-reactive center, in Hg methylation.

Mercury methylation independent of the acetyl-coenzyme A pathway in sulfate-reducing bacteria.

Sulfate-reducing bacteria (SRB) in anoxic waters and sediments are the major producers of methylmercury in aquatic systems. Although a considerable amount of work has addressed the environmental factors that control methylmercury formation and the conditions that control bioavailability of inorganic mercury to SRB, little work has been undertaken analyzing the biochemical mechanism of methylmercury production. The acetyl-coenzyme A (CoA) pathway has been implicated as being key to mercury methylation in one SRB strain, Desulfovibrio desulfuricans LS, but this result has not been extended to other SRB species.