11/06/2011
Permafrost Microbes Could Make Impacts of Arctic Warming Worse
collected Researchers collected three intact frozen permafrost soil cores with their overlying seasonally thawed active layers from Hess Creek, Alaska.
The Science
In Earth’s Arctic regions, frozen soils (permafrost) sequester an estimated 1.6 trillion metric tons of carbon, more than 250 times the amount of greenhouse gas emissions attributed to the United States in 2009. Concerns are growing about the potential impact on the global carbon cycle when rising temperatures thaw the permafrost and release the trapped carbon. Microbes may significantly influence the eventual outcome through their involvement in carbon cycling. New research on permafrost microbes has discovered a previously unknown, yet abundant microbe that produces methane, a far more potent greenhouse gas than carbon dioxide. A draft of this microbe’s genome was determined by assembling DNA fragments isolated from permafrost. The DOE Joint Genome Institute (JGI) had previously identified several microbes that produced methane (“methanogens”) as a metabolic byproduct, and used this knowledge to identify enough fragments of the new microbe’s DNA to assemble a draft of its genome. The abundance of this novel methanogen implies that it could be an important factor in methane production under permafrost thawing conditions. The research, published in Nature, was carried out by scientists at JGI, Lawrence Berkeley National Laboratory, and U.S. Geological Survey.
Summary
Researchers use deep metagenomic sequencing to determine the impact of thaw on microbial phylogenetic and functional genes, and relate these data to measurements of methane emissions. Metagenomics, the direct sequencing of DNA from the environment, allows the examination of whole biochemical pathways and associated processes, as opposed to individual pieces of the metabolic puzzle. This metagenome analyses reveal that during transition from a frozen to a thawed state there are rapid shifts in many microbial, phylogenetic and functional gene abundances and pathways. After one week of incubation at 5 °C, permafrost metagenomes converge to be more similar to each other than while they are frozen. Researchers find that multiple genes involved in cycling of C and nitrogen shift rapidly during thaw. The team also constructs the first draft genome from a complex soil metagenome, which corresponds to a novel methanogen. Methane previously accumulated in permafrost is released during thaw and subsequently consumed by methanotrophic bacteria. Together these data point towards the importance of rapid cycling of methane and nitrogen in thawing permafrost.
Principal Investigator
Janet K. Jansson
DOE Joint Genome Institute
BER Program Manager
Ramana Madupu
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Biological Systems Science Division
[email protected]
References
Mackelprang, R., M. P. Waldrop, K. M. DeAngelis, M. M. David, K. L. Chavarria, S. J. Blazewicz, E. M. Rubin, and J. K. Jansson. 2011. “Metagenomic Analysis of a Permafrost Microbial Community Reveals a Rapid Response to Thaw,” Nature 480, 368-71. DOI: 10.1038/nature10576.