Life in Deep Salts

The deep subsurface biosphere plays an important role in the global cycling of elements, with implications for climate change, deep subsurface repositories and the oil industry. Yet we know very little about what organisms exist in the deep subsurface and how they gain their energy and carbon. We use a combination culture and culture-independent methods to answer questions about deep subsurface communities in an ancient Permian salt deposit. The results show that the communities are dominated by chemoorganotrophs, suggesting fixed organic carbon is essential to the community, in spite of the carbon limited environmental conditions and lack of photosynthesis in the deep subsurface. These chemoorganotrophs use a number of different carbon sources for growth. However, the lack of a viable autotrophic community indicates that these communities may be dependent on ancient buried carbon for growth. Ongoing work aims to identify this carbon source, whilst also examining how the microbial community is shaped by the Permian ocean chemistry which deposited the salt. Finally, these deep subsurface data may tell us about conditions of habitability on other planetary bodies with salts, such as Mars.