Microbial communities and biomineralization potential within mountain permafrost of the Devaux ice cave in the Central Pyrenees

Ice caves constitute one of the last cryospheric environments studied in the meridional regions. They are undergoing a pronounced ice reduction, and are an important example of ecosystems that have not yet been thoroughly explored from a microbiological point of view. The Devaux cave, in the Central Pyrenees, still hosts perennial ice. To test whether this ice contained microbial communities, prokaryotic and eukaryotic microorganisms were searched by sequencing their 16S and 18S rRNA genes. From the taxonomic information, the potential functional pathways of these communities were predicted using bioinformatic techniques. In addition, the genome of the microorganisms housed in the perennial ice samples was investigated, and through metagenomic studies their metabolic capacity was elucidated. The cryogenic mineralization of the Devaux cave leads to the production of various Ca and Mg carbonates: calcite, aragonite, vaterite, Mg-rich calcite, and nesquehonite, whose formation may have been favored by the microorganisms in the cave. Among the genes encoding enzymes that enable reactions involved in biomineralization, those belonging to the nitrate and sulfate reduction dissimilatory pathways as well as ureases, ammonia lyases, and carbonic anhydrases were identified. This research takes a further step in the investigation of biomineralization, using the Devaux cave as a model.