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Microbial response to the thawing Arctic

The frozen Arctic soils keep an estimated 1,672 billion metric tons of carbon out of the Earth’s atmosphere, more than 250 times the amount of greenhouse gas emissions attributed to the United States in the year 2009. Rising global temperatures have led to increasing concerns on the potential impacts of thawing permafrost upon the carbon cycle.

USGS researchers tap the Arctic permafrost for soil samples that can be studied to assess 
their microbial composition and the impact of these populations by thawing conditions. 
(Courtesy of Mark Waldrop, USGS Soil Carbon Research)

Researchers led by former DOE JGI postdoctoral researcher Rachel Mackelprang and Berkeley Lab senior scientist Janet Jansson collaborated with the U.S. Geological Survey to understand how the microbes found in permafrost respond to their warming environment. With the frozen soils “poised to become a major source of greenhouse gases,” Jansson said, metagenomics can help researchers understand how currently uncultivated and unstudied microbes there cycle carbon and release greenhouse gases during a thaw.

 
Mackelprang and her colleagues generated nearly 40 billion bases of raw DNA sequence from samples cored by the USGS and  identified several microbes that produced methane as a byproduct. Among their findings, published online November 6, 2011 in the journal Nature, is the first draft genome of a novel methanogen assembled out of the permafrost soil metagenome. They wrote that the novel microbe’s abundance indicates it could be a major player in methane production. Additionally, they found that the same microbe had genes for nitrogen fixation, making this study also the first to describe a potentially nitrogen-fixing methanogen in permafrost soil.