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Permafrost represents a largely understudied genetic resource. Thawing of permafrost with global warming will not only promote microbial carbon turnover with direct feedback on greenhouse gases, but also unlock an unknown microbial diversity. A few pioneering metagenomic efforts have unravelled the permafrost microbiome in polar regions, but surveys in temperate mountain permafrost have largely been neglected. We applied a unique experimental design coupled to high-throughput sequencing of ribosomal markers to characterize the microbiota at the long-term alpine permafrost study site Muot-da-Barba-Peider in eastern Switzerland with an approximate 14C radiocarbon age of 12,000 years. Compared to the active layers, the microbiome within permafrost was more diverse and enriched with members of the superphylum Patescibacteria (OD1, TM7, GN02, OP11) as well as other candidate phyla. These understudied phyla with no cultured representatives proposedly have small streamlined genomes with reduced metabolic capabilities and adaptations to anaerobic, fermentative metabolisms. The permafrost microbiota was also enriched with cold-adapted yeasts, lichenized fungi, and archaeal members of the Thermoplasmata. These data yield an unprecedented view on microbial life in temperate mountain permafrost, which is increasingly important for our understanding of the biological dynamics of permafrost in order to anticipate potential ecological trajectories in a warming world. |