Active microbiota persist in dry permafrost and active layer from Elephant Head, Antarctica

Abstract

Dry permafrost is a challenging environment for microbial life due to the cold, dry, and often oligotrophic conditions. In 2016, Elephant Head, Antarctica was confirmed as the second site on Earth to contain dry permafrost. It is geographically distinct from the McMurdo Dry Valleys where dry permafrost has been studied previously. Here we present the first study of the microbial activity, diversity, and functional potential of Elephant Head dry permafrost. Microbial activity was measured using radiorespiration assays with radiolabelled acetate as a carbon source at 5, 0 and − 5°C. Low, but detectable, rates of microbial activity were measured in some samples at 0 and − 5°C. This is distinct from previous studies of McMurdo Dry Valley dry permafrost which concluded that dry permafrost represents a cold-arid limit to life on the planet. The isolation of cold adapted organisms from these soils, including one capable of sub-zero growth further supports that Elephant Head dry active layer and dry permafrost harbor viable microbial life which may be active in situ. Metagenomic, 16S rRNA gene and ITS and amplicon sequencing identified similar microbial communities to other Antarctic and cold environments. The Elephant Head microbial community appears adapted for survival in cold, dry, and oligotrophic conditions based on the presence of cold adaptation and stress response genes in the metagenomes. Together our results show that dry permafrost environments do not exclude active microbial life at sub-zero temperatures and suggests that the cold, dry soils of Mars may also not be as inhospitable as previously thought.