Adaptation to redox conditions and substrate availability differentiate permafrost microbial communities from across the globe

Rachel Mackelprang, Biology, California State University, Northridge, Northridge, CA, Neslihan Tas, Lawrence Berkeley National Laboratory, Mark P. Waldrop, Geology, Minerals, Energy, and Geophysics Science Center, US Geological Survey, Menlo Park, CA, Christopher Chabot, Biology, US Army Corps of Engineers, Los Angeles, CA, Susanne Liebner, Geomicrobiology, GFZ German Research Centre for Geosciences, Potsdam, Germany and Mary-Catherine Leewis, US Geological Survey

Background/Question/Methods
Permafrost underlies approximately 24% of land in the Northern Hemisphere and contains 25-50% of the total global soil carbon pool. Frozen conditions protect permafrost carbon from microbial metabolism, but anthropogenic activities threaten to induce large-scale permafrost thaw. The resulting microbial degradation is predicted to release globally significant quantities of greenhouse gasses into the atmosphere. However, difficulty in accessing permafrost samples and the high diversity of microbial communities has throttled efforts to understand the global distribution of taxa and their functional traits.
Results/Conclusions
Here, we analyzed over 100 permafrost metagenomes across North America, Europe, and Asia. In stark contrast to non-permafrost soils, communities did not cluster into ecological groups corresponding to permafrost age, continent, or commonly measured soil and environmental characteristics such as pH. Instead, site to site variation was the most important driver of assemblages, indicating the importance of site history and other yet-unknown factors. Genes differing most significantly between sites were related to energy metabolism, substrate availability, and redox conditions. Together, these data highlight the importance of further investigations to unravel the interactions between microbial communities and permafrost attributes, which may be crucial for ongoing modeling and prediction efforts.