How Arctic microbes respond to a warming world

November 6, 2011
How Arctic microbes respond to a warming world
This is an image of one of the core samples retrieved from the permafrost at Hess, Creek Alaska, by USGS scientists. Credit: Courtesy of USGS Soil Carbon Research



"The permafrost is poised to become a major source of greenhouse gases as the temperature in the Arctic is expected to increase dramatically compared to the expected temperature increase in many other regions of the world," said ESD's Janet Jansson, corresponding author and initiator of the study (first supported by a grant to her from DOE Laboratory Directed Research and Development funds). "By applying metagenomics to study microbial community composition and function, we can help to answer questions about how the currently uncultivated and unstudied microbial species residing in permafrost cycle organic carbon and release greenhouse gases during thaw," Jansson said. "This will provide valuable information that could lead to improved models and eventual mitigation strategies."


Waldrop cored meter-deep permafrost samples from a peaty black spruce forest along Hess Creek, Alaska. Each sample was then divided to distinguish between the seasonally thawed "active" layer, which comprised the top third of the core, and the permanently frozen "permafrost" horizon underneath. The samples were incubated during thaw at 5°C and then sent to the Jansson lab for DNA extraction and analyses At the DOE JGI, the team led by Director Eddy Rubin and his postdoctoral fellow Rachel Mackelprang, (now at California State University-Northridge) sequenced microbial DNA from the samples. "These microbial communities are extremely diverse," said Mackelprang. "A single gram of soil may contain thousands of different bacterial species and billions of cells. Additionally, most of these microbes cannot be grown in the laboratory, making this an extremely difficult area to study." The data were then analyzed in collaboration with Jansson and her team at ESD, including Kristen DeAngelis, Maude David, and Krystle Chavarria.

At DOE JGI, Mackelprang and her colleagues generated nearly 40 billion bases of raw DNA sequence, necessary due to the high microbial diversity of the soil. They identified several microbes that produced methane as a byproduct, and were able to assemble a draft genome of a novel methanogen. "This is the first example of a successful assembly of a draft genome from a highly complex soil metagenome," the authors wrote. "The abundance of this novel methanogen suggests that it may be an important player in methane production under frozen conditions." Additionally, the genomic data revealed that the microbe had genes for nitrogen fixation, making this study also the first to describe a potentially nitrogen-fixing methanogen in permafrost soil.

The researchers identified many genes involved in carbon and nitrogen cycling in the metagenomic data, and found that their levels of abundance shifted in response to their thawing habitat. "These detailed analyses reveal for the first time the rapid and dynamic response of permafrost microbial communities to thaw," they concluded. "The thaw-induced shifts that we detected directly support conceptual models of carbon and nitrogen cycling in arctic soils, in which microbes play a central role in and destabilization of stored ."

Explore further: Thawing permafrost likely to boost global warming

Related Stories

Thawing permafrost likely to boost global warming

September 1, 2008


Arctic soil reveals climate change clues

October 8, 2008


Recommended for you

Head and body lice read DNA differently

July 28, 2015


1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

1 / 5 (3) Nov 07, 2011
Pollution and the defeat of the smoggy 70s are real but
death by CO2 is not. Thankfully, (at least to real planet lovers), it was an academic
exaggeration fueled by political correctness and unconscionable news editors. And
we should be happy for that. Not disappointed that a CO2 crisis wasnt real.
If these are not good enough reason s for anyone stop supporting the CO2
mistake, history will watch you condemn your own children to the greenhouse gas
chambers with sickening glee.


Click here to reset your password.