With the altitude of 3570 m, this is so far the highest site where actively forming non-lithified stromatolites have been found, located at the shore of a volcanic, alkaline lake Socompa (Argentina). These microbial communities are a hotspot of biodiversity thriving under harsh environmental conditions that might be compared to Early Earth. This study uses a WGS strategy to understand the unique community composition and the mechanisms used by their members to withstand the extreme environment.