Scientists use genes to transform inorganic into organic mercury

By identifying two genes required for transforming inorganic into organic mercury, which is far more toxic, scientists today have taken a significant step toward protecting human health.

The question of how methylmercury, an organic form of mercury, is produced by natural processes in the environment has stumped scientists for decades, but a team led by researchers at Oak Ridge National Laboratory has solved the puzzle.

Results of the study, published in the journal Science, provide the genetic basis for this process, known as microbial mercury methylation, and have far-reaching implications.

"Until now, we did not know how the bacteria convert mercury from natural and industrial processes into methylmercury," said ORNL's Liyuan Liang, a co-author and leader of a large Department of Energy-funded mercury research programme that includes researchers from the University of Missouri-Columbia and University of Tennessee.

"This newly gained knowledge will allow scientists to study proteins responsible for the conversion process and learn what controls the activity," said Liang, adding that it may lead to ways of limiting methylmercury production in the environment.

For some 40 years scientists have known that when mercury is released into the environment certain bacteria can transform it into highly toxic methylmercury. Exactly how bacteria make this happen has eluded scientists. The challenge was to find proteins that can transfer a certain type of methyl group and to identify the genes responsible for their production.