Mercury munching microbes (om nom nom)

by Tyler Shendruk

Published: 9/30/10

The problem
THE MAJORITY OF MERCURY in the atmosphere is generated by human industries like coal combustion and gold mining. The rest comes from natural sources such as volcanoes and forest fires. Either way, when mercury is dispersed into the atmosphere, it is carried poleward where it is oxidized and becomes heavier, falling into sensitive Arctic regions as a toxic contaminant.
Mercury binds to proteins and then accumulates in organisms, causing mercury compounds from the environment to enter the Arctic’s atmosphere when they get soaked up by the tiny microbes that form the ecosystem’s foundation. Since there’s nowhere for it to go, mercury is passed from prey to predator. Eventually, high levels of mercury accumulate in the top of the food chain—that’s us, friend.

The researcher
Alexandre Poulain, a professor at the U of O, studies how microbes alter the mobility and the toxicity of metals and metalloids in the environment. He focuses on aquatic systems in polar regions and ventures out into the Arctic to bring samples home for analysis in his lab.

The project
Anaerobic microbes, bacteria that don’t use oxygen, alter the nature of the mercury. Some make metals more toxic by turning ordinary mercury into very harmful methylmercury. Dissimilarly, other bacteria break down methylmercury, making a gas and venting it out of the ecosystem. Poulain looks at the difference between the rates of these two processes by analyzing the production of proteins (ribonucleic acid or RNA) that control whether microbes create toxic mercury or whether they detoxify the Arctic atmosphere.

The key
Upon sensing mercury in their environment, certain northern microbes activate genes naturally encoded in their DNA. Poulain can determine which of these genes are active in biomass samples from polar regions and can even tell exactly which genes are needed to defend against the toxic nature of mercury.
Poulain’s goal is to bridge global-scale environmental science and microscopic biology The reduction of Arctic mercury by tiny microbes plays a major role in regulating the toxicity of the Far North and could possibly be used in integrated approaches to environmental management.