Groundwater microbial communities from subsurface biofilms in sulfidic aquifer

Sulfur is one of the 10 most abundant elements in the galaxy, and its complex redox chemistry and tendency to polymerize have lead to a comparably complex array of microbial sulfur metabolisms linking carbon, sulfur, nitrogen and iron in biogeochemical cycles. The deep and sulfidic Frasassi aquifer has emerged as a model system for studying sulfur cycling in the terrestrial subsurface due to its accessibility to human exploration. Detailed studies of the geochemistry of the limestone-hosted Frasassi aquifer indicate that the microbial community is directly dependent on reducing power contained in ancient organic matter in stratigraphically adjacent shales, as well as oxidants in evaporites underlying the shales (sulfate, nitrate). This juxtaposition of rock types is common in sedimentary rock sequences globally, and thus the aquifer at Frasassi may reveal subsurface processes, metabolisms, and microbial taxa which have global significance.