Mercury methylation by bacteria.

Bacteria capable of methylating Hg2+ have been isolated from sediment, water, soil and the gastrointestinal tract of humans. However, very little is known about the physiology and genetics of the mechanisms controlling Hg2+ methylation. Mercury methylation can be either chromosomal or plasmid-encoded in bacteria. In addition, the extent of nonbiological methylation is not well understood in environmental samples, where there are numerous physical, chemical and biological factors that control the methylation process. It is known that methylation of Hg2+ is mediated by a series of enzymatic reactions that are also responsible for the anaerobic evolution of methane. However, under highly reduced environments the reaction can also occur nonbiologically. It is possible that certain bacteria use methylation as a resistance/detoxification mechanism.