Bacterial genome may hold answers to mercury mystery

A bacterium called Desulfovibrio desulfuricans strain ND132 can transform elemental mercury into methylmercury, a human neurotoxin.

A bacterium called Desulfovibrio desulfuricans strain ND132 can transform elemental mercury into methylmercury, a human neurotoxin.

A newly sequenced bacterial genome from a team led by the Department of Energy's Oak Ridge National Laboratory could contain clues as to how microorganisms produce a highly toxic form of mercury.

Methylmercury, a potent human neurotoxin, appears in the environment when certain naturally occurring bacteria transform inorganic mercury into its more toxic cousin. Few bacterial species are capable of this conversion, and exactly how the transformation takes place has been a matter of debate for decades.

"What is not known are the genes or the proteins that allow these bacteria to mediate the transformation," said ORNL's Steven Brown, who led a research team to sequence the genome of a bacterium in the Desulfovibrio genus that is capable of methylating mercury.

The new genome, sequenced at the California-based DOE Joint Genome Institute (JGI) and published in the Journal of Bacteriology, lays the foundation for future research to examine the little understood mechanisms behind the production of methylmercury.

Desulfovibrio desulfuricans strain ND132 is an organism that thrives in sediments and soils without oxygen - the places in lakes, streams and wetlands where mercury contamination is converted to methylmercury.