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05/21/2014

How Microbes Deal with Permafrost

Source:  Neslihan Tas, Janet Jansson and Dan Hawkes

Janet_neslihanIn an issue of Nature Reviews Microbiology out this week (May 12, 2014), ESD microbiologists Janet Jansson and Neslihan Tas reveal new data on the microbial ecology of permafrost. Their work leads the way toward a new understanding of the strategies microbes use to cope with frozen conditions, as well the influence of climate change on microbial life.

Today’s Earth is a cold planet, where an estimated 25% of all land area contains permafrost—permanently frozen soil.  Permafrost is different from all other soil habitats, in that it contains ice. There are areas of the Arctic where permafrost is up to 3 million years old, and in areas of Antarctica it can be even older. Moreover, parts of the land surface that are now permafrost were not frozen at earlier times, and may have been covered by water and vegetation. Plant, animal, and microbial biomass that accumulated during warm periods may be preserved within the permafrost during subsequent freezing. While plants and animals trapped during this transition died off, many of the microorganisms were likely able to survive, adapt, and remain active.

In this paper, Jansson and Tas summarize the state of scientific knowledge regarding the microbial ecology of permafrost. As Jansson notes, “Recent developments in molecular ‘omics’ technologies have enabled glimpses into the relatively unexplored world of permafrost microbiology and have shown that there is microbial life in permafrost, and that these microbes and their ability to produce greenhouse gases are impacted by climate change.”

Permafrost_fig2
Permafrost thaw features at lowland and highland elevations.

In addition to the interest generated by advanced genomic technology, there is the scientific challenge of understanding the possible feedbacks from carbon cycling by microbes currently sequestered in permafrost. Tas finds that permafrost-containing regions are experiencing accelerated warming, which means that “the consequences of global temperature increase will be strongly felt in fragile Arctic systems.” Subsequent permafrost thaw will probably not only result in increased activation of indigenous permafrost microorganisms, but will also release sizable amounts of carbon and nutrients that can be used for their accelerated growth.

Permafrost_fig3
Microbial composition of permafrost from different geographical locations.

Permafrost thaw from climate change also results in changes in soil physical and chemical properties. For example, in uplands of Alaska, permafrost thaw could result in drainage of water trapped in permafrost and drying of deep soils. In contrast, on the Alaskan North Slope, permafrost thaw results in collapse and rise of soil, creating polygonal grounds and ponds. As Tas says, “We are just beginning to understand the consequences of such changes on soil microbial communities and their activity. Projects like DOE’s Next Generation Ecosystem Experiment (NGEE)-Arctic, which combines ecosystem research and modeling, will help microbiologists unlock the mysteries contained in complex Arctic microbial communities and their interactions with the changing environment.”

Tas points to other possible applications for this research. “Besides the possible climate impacts,” she notes, “permafrost is intrinsically interesting for a microbiologist, as it is a unique habitat for cold-adapted microbial life on Earth and a likely model system for extraterrestrial biomes.”

To read more, go to:

http://www.nature.com/nrmicro/journal/vaop/ncurrent/full/nrmicro3262.html

Citation: Jansson, J.K., and N. Tas (2014), The microbial ecology of permafrost. Nature Reviews Microbiology, DOI:10.1038/nrmicro3262, May 12, 2014.

Funding Source: BER NGEE