Novel Methanogenic Microbe Discovered in Thawing Permafrost
Northern high-latitude ecosystems are undergoing rapid changes with rising temperatures catalyzing the transition of many permafrost sites to wetlands. As the organic carbon locked in permafrost thaws, it becomes accessible to decomposition by microbial communities. Understanding of these communities is limited, especially regarding functional processes that impact rates of carbon degradation and the balance of carbon dioxide (CO2) versus methane (CH4) released to the atmosphere. In a new U.S. Department of Energy Genomic Science Program study led by researchers at the University of Arizona, a combination of metagenomics, metaproteomics, and geochemical flux measurements were used to characterize microbial community structure and function at a thawing permafrost site in northern Sweden. A new species of archaea, Candidatus Methanoflorens stordalenmirensis, was found to dominate methanogen populations in the thawing active layer of permafrost. Using deep metagenomic sequencing, the team was able to assemble a nearly complete genome from this organism and identify the metabolic pathway for methanogenesis—consumption of hydrogen and CO2 and production of CH4. Measurements of CH4 flux at the thawing permafrost site and quantitative in situ detection of M. stordalenmirensis methanogensis proteins suggest that this organism may perform the majority of methane production at these sites, especially during thawing. The team also searched published metagenomic libraries collected from permafrost sites across the northern hemisphere and detected closely related methanogens at high numbers in the majority of sites. The dominance of a single organism in methane production is a surprising finding. Given evidence for the global distribution of this type methanogen in thawing permafrost sites, these results may have wide-ranging implications for understanding of climate change impacts.
Mondav, R., B. J. Woodcroft, E.-H. Kim, C. K. McCalley, S. B. Hodgkins, P. M. Crill, J. Chanton, G. B. Hurst, N. C. VerBerkmoes, S. R. Saleska, P. Hugenholtz, V. I. Rich, and G. W. Tyson. 2014. “Discovery of a Novel Methanogen Prevalent in Thawing Permafrost,” Nature Communications 5, DOI: 10.1038/ncomms4212.