Microbes to the rescue in the Far North

Microbes, with their ability to alter the fate of contaminants, can help clean up the Arctic.

by Isabelle Marquis

The Arctic is a sensitive area. Contaminants originating thousands of miles away can show up in this fragile ecosystem. These “global pollutants” travel great distances via air masses. When development of the Arctic subsoil begins, the ecosystems will become even more fragile. What can be done to reduce the risks associated with contaminants of global and local origins in this northern ecosystem?

Alexandre Poulain, microbiologist and researcher at the University of Ottawa, is interested in how microbes interact with contaminants, particularly toxic metals, in cold environments. “Microbes, and particularly bacteria, have incredible metabolic diversity and can either make metals more toxic or, conversely, transform them into a less toxic form,” explains Poulain. “Since mining activities seem inevitable in polar regions, I am concentrating my research efforts on understanding the process that allows microbes to alter the toxicity of metals. My hope is that this will allow us to better manage Arctic ecosystems and lead to sustainable use of the resources,” he says.

Professor Poulain is particularly interested in mercury, a metal that occurs naturally in the environment and that is being increasingly dispersed in the environment through human activity. Mercury becomes very toxic when it is converted to methylmercury. This toxic compound readily accumulates in organisms and is bioamplified in food webs. As a result, top-level predators in aquatic ecosystems, mainly fish, can exhibit very high levels of this toxin. The health of humans and wildlife consuming the fish is then threatened. 

But what role do microbes play in this picture? Certain bacteria living in the dark and anoxic environment of aquatic systems are responsible for the formation of the toxin methylmercury, while others can actually contribute to the detoxification of this dangerous compound. However, the relative importance of these two reactions— production and detoxification—in polar ecosystems remains poorly understood. Professor Poulain’s recent work has shown that thanks to certain arctic bacteria, detoxification can occur during polar springtime. The results of his work suggest possibilities for developing remediation strategies for contaminated sites in the Far North. 

To evaluate the impact microbes have on their environment, Alexandre Poulain conducts work both in the lab and out in the field. In the lab, he develops biosensors, microorganisms that have been isolated from cold regions and then genetically modified to report on how they interact with their environment and, in particular, with contaminants. Using these biosensors, the research team tries to identify, at the genetic level, the metabolic pathways involved in altering the cycle of the contaminants either positively (by detoxifying) or negatively (by forming toxins). Once the scientists know which genes are likely involved, they can develop biological probes that will track these pathways. When Poulain and his team go out into the field, they use these probes together with the information collected in the lab to test the validity of the information and map the microbial transformations in situ. Through chemical and physical characterization of the test site, this multidisciplinary approach helps better predict and manage the impact of contaminants on the ecosystem.

When contaminants accumulate in food webs, they pose a risk to the health of the organisms that depend on these networks of food chains. By controlling the ability of microbes to reduce the hazardous effect of different pollutants, it is possible to reduce the risk of polluting northern regions and mitigate potential harmful effects on human and wildlife health. “We are trying to optimize natural ability of microbes to break down contaminants and, as a result, clean up the environment,” explains Alexandre Poulain. 

Toxic metals are, however, only one of the many stresses imposed on Arctic ecosystems. With the current environmental changes we are experiencing and as temperatures rise, ground that has been frozen for thousands of years could become very active. And we have no idea of the direct or indirect effects of this thawing on the fate of contaminants, explains the researcher. “In addition, under the effects of microbial activity, organic matter contained in the frozen ground may produce huge quantities of greenhouse gases, dramatically increasing the rate of global warming.” 

This potential risk—the expected extent of which we have no way of measuring—together with the known risks highlight how important it is to address the problem of contamination of polar regions. That a problem so large could be solved with the help of tiny microbes reminds us that “great acts are made up of small deeds.” 

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