Haloarchaeal communities in hypersaline brines from the deep subsurface encode the genomic potential for chemolithoautotrophy.

Carbon capture and storage technologies have increasingly gained attention as part of a global energy transition towards net zero carbon dioxide emissions. Carbon capture and storage aims to store vast quantities of carbon dioxide in the terrestrial and marine subsurface. This technology targets saline aquifers among other formations, with the salinity of some aquifers being hypersaline. However, little is known about the microbial impacts of halophilic communities on the success of permanent carbon dioxide storage. Hence, expanding our knowledge on community composition, functional potential, and the ecology of the hypersaline subsurface is a crucial step towards understanding how these systems will respond to large scale carbon dioxide injections. In this study, we analysed metagenome sequencing data from four hypersaline brines sampled approximately 1km below the Earths surface, one of which was contaminated with crude oil. Alongside the metagenomic analysis, in total 15 brines have been analysed for their geochemistry and community structure based on 16S rRNA gene sequencing.