Researchers find life supported by hydrogen under glaciers

Using years of data collected from ice-covered habitats around the world, a Montana State University team discovered new perspectives on the processes that support microbial life under ice sheets and glaciers and the role these organisms play in perpetuating life by ice ages and perhaps in seemingly inhospitable environments on other planets.

PhD candidate Eric Dunham from the Department of Microbiology and Immunology at MSU College of Agriculture, along with mentor Eric Boyd, published their findings in the journal The works of the National Academy of Sciences this week. The paper examines how water and microbes interact with the bedrock beneath glaciers, using sediment samples taken from glacial sites in Canada and Iceland.

“We continued to find organisms in these systems that were supported by hydrogen gas,” said Boyd, who inspired the project. “It didn’t make sense at first, because we couldn’t figure out where that hydrogen gas came from under these glaciers.”

A team of researchers, including Boyd, later discovered that through a series of physical and chemical processes, hydrogen gas is produced as the silica-rich bedrock beneath glaciers is ground into small mineral particles by the weight of the ice above. it. When those mineral particles combine with glacial meltwater, they remove hydrogen.

What became even more fascinating to Boyd and Dunham was that microbial communities beneath glaciers could combine that hydrogen gas with carbon dioxide to generate more organic matter, called biomass, through a process called chemosynthesis. Chemosynthesis is similar to how plants generate carbon dioxide biomass through photosynthesis, although chemosynthesis does not require sunlight.

To learn more about what those chemosynthetic microbes were doing, Dunham used sediment samples from glaciers in Canada and Iceland. He cultured samples of living organisms found in the sediment in a laboratory, watching them for several months to see if they would continue to grow in the simulated environment.

“The organisms we were interested in rely on hydrogen gas as food to grow and most are also anaerobic, which means that oxygen will kill them,” said Dunham, who is originally from Billings and enters the last semester of his doctoral studies. “One of the most critical steps in preparing these experiments and the most stressful element was to put the samples in bottles and wash away all the oxygen as quickly as possible, so I didn’t kill the organisms I was trying to study. “

Over the months of microbial culture preparation and observation, Dunham found that not only was it possible to track the growth of communities in the laboratory environment, but also that the type of bedrock that underlies a glacier influenced the amount of hydrogen gas produced in the presence of microbial communities that have been better adapted to hydrogen metabolism. Samples from the Kötlujökull Glacier in Iceland, which is above the basaltic bedrock, produced much more hydrogen gas than samples from the Robertson Glacier in Alberta, Canada, which has carbonaceous rock beneath it.

As it uses that gaseous hydrogen to generate energy, Boyd said, microbes also draw carbon dioxide from the air to create biomass, replicate and grow. The ability to “fix” carbon is a critical process of climate regulation, another resemblance to plant photosynthesis.

“Given that glaciers and ice sheets now cover about 10% of the Earth’s land mass and a much larger fraction sometimes in the planet’s past, microbial activities such as those measured by Eric are likely to have a major impact on the Earth’s climate,” both today and in the past, “Boyd said.” We’ve known for some time that microorganisms that live under ice sheets or glaciers can fix carbon, but we never really understood how. Eric’s pioneering work shows that not only these organisms are completely self-sustaining in the sense that they can generate their own fixed carbon, they also don’t need sunlight to make it like the rest of the biosphere we’re familiar with. “

Looking further into the other planets in our solar system, Boyd observes that two of the critical elements that scientists look for when evaluating housing are water and an energy source. The new knowledge that self-sustaining microbial communities can thrive in frozen environments by generating hydrogen gas is a critical step toward identifying potentially habitable environments on other planets.

“There is a lot of evidence for ice and glaciers on other planets,” he said. “Are they habitable? We don’t know. Could there be microbes living under layers of ice on planets with a bedrock similar to the ones Eric studied? Absolutely. There’s no reason to think otherwise.”

For Dunham, whose undergraduate and postgraduate research focused on health sciences and virology before moving to biogeochemistry, the most rewarding part of the new discovery is exploring how different Earth processes fit and influence each other. each other in ways that the scientific community is just beginning to unblock. .