Unraveling a Microbial Mystery

Why Are Some Bacteria Making Environmental Mercury Even More Toxic?
April 4, 2023
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Smithsonian Environmental Research Center (SERC) scientists are working to understand why some bacteria convert mercury in the environment to its most toxic form, methylmercury. Humans and animals regularly consume methylmercury because it is concentrated in the tissues of organisms as it moves up the food chain. Understanding more about the bacteria that produce this powerful neurotoxin, through a process known as mercury methylation, may provide clues to mitigating its risks.  

In a recently published article in the journal Applied and Environmental Microbiology, SERC researchers reveal that a link between microbial mercury methylation and arsenic resistance may hold clues to the evolution of the genes responsible for mercury methylation.

“This is the first hint of how or why this nasty process might have evolved,” said Cynthia Gilmour, co-author and SERC scientist. “We previously did not understand why microbes conducted mercury methylation. Our work suggests that it might have evolved from, or in parallel to, arsenic resistance.” 

This line of research began when lead author and SERC researcher, Caitlin Gionfriddo, discovered that the genes responsible for methylation and arsenic resistance were next to each other. This research may help scientists better predict where mercury methylation happens in nature because that process could be stimulated by the presence of arsenic. 

Gionfriddo believes this research may hold the keys to greater understanding and predictive abilities for where methylmercury occurs in nature. “Our next steps will be to look for evidence of arsenic driving microbial mercury methylation in the environment.” 

As science sheds light on the microbes responsible for producing methylmercury and where they live, that information can be used to limit its presence in the food supply. 

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