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Appl Environ Microbiol, March 1998, p. 1013-1017, Vol. 64, No. 3
0099-2240/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.

Mercury Methylation and Demethylation in Anoxic Lake Sediments and by Strictly Anaerobic Bacteria

K.-R. Pak and R. Bartha^*

Department of Biochemistry and Microbiology, Cook College, Rutgers University, New Brunswick, New Jersey 08903-0231

Received 10 October 1997/Accepted 29 December 1997

After spiking anoxic sediment slurries of three acidic oligotrophic lakes with either HgCl₂ at 1.0 µg/ml or CH₃HgI at 0.1 µg/ml, both mercury methylation and demethylation rates were measured. High mercury methylation potentials were accompanied by high demethylation potentials in the same sediment. These high potentials correlated positively with the concentrations of organic matter and dissolved sulfate in the sediment and with mercury levels in fish. Adjustment of the acidic sediment pH to neutrality failed to influence either the methylation or the demethylation rate of mercury. The opposing methylation and demethylation processes converged to establish similar Hg²⁺-CH₃Hg⁺ equilibria in all three sediments. Because of their metabolic dominance in anoxic sediments, mercury methylation and demethylation in pure cultures of sulfidogenic, methanogenic, and acetogenic bacteria were also measured. Sulfidogens both methylated and demethylated mercury, but the methanogen tested only catalyzed demethylation and the acetogen neither methylated nor demethylated mercury.

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^* Corresponding author. Mailing address: Department of Biochemistry and Microbiology, Lipman Hall, Room 322, Cook College, Rutgers University, P.O. Box 231, New Brunswick, NJ 08903-0231. Phone: (732) 932-9763, ext. 322. Fax: (732) 932-8965.

New Jersey Agricultural Experiment Station publication no. D-01408-01-97.

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