Microbes that live in rice paddies, northern peat bogs and other previously unexpected environments are among the bacteria that can generate highly toxic methylmercury, researchers at Oak Ridge National Laboratory and the Smithsonian Environmental Research Center have learned.
This finding, published in Environmental Science and Technology, explains why deadly methylated mercury is produced in areas where the neurotoxin's presence has puzzled researchers for decades. Methylmercury the most dangerous form of mercury damages the brain and immune system and is especially harmful to developing embryos. Certain bacteria transform inorganic mercury into toxic methylmercury.
The discovery also validates the recent finding that two genes are essential for the methylation of mercury. Previously, only a narrow range of microbes were recognized as mercury methylators, said co-author Dwayne Elias of the Department of Energy laboratory's Biosciences Division.
"We showed for the first time that many different types of bacteria are able to produce this potent neurotoxin," Elias said. "The newly identified microbes include methane-producing organisms that live in rice paddies, anaerobic wastewater treatment plants, northern peat lands and possibly within our bodies."
Elias and colleagues are testing a bacterium from the human intestine that they predict will also methylate mercury. Other bacteria able to transform inorganic into methylmercury include those used in biological dechlorination and metal treatment systems. All of these organisms are anaerobic, which means they grow in habitats without oxygen, including aquatic sediments and wetland soils.
By identifying these organisms, the researchers may have explained why methylmercury is accumulating in unexpected places. The discovery may also help clarify how methylmercury is produced in the open ocean, according to co-author Cindy Gilmour of the Smithsonian Environmental
|Contact: Ron Walli|
DOE/Oak Ridge National Laboratory