The objective of this project is to determine the diversity, phylogeny, and expression of functional genes involved in carbon, hydrogen, and sulfur cycling in North Pond crustal fluids. These formation fluids are expected to be representative of the ubiquitous cold ocean crust habitat, where reactions between the water and mineral rock surfaces create substrates suitable for sustaining a potentially large reservoir of microbial life. Information regarding crustal microbial communities and the energy sources available for microbial metabolism has been limited by the inaccessibility of samples. IODP Expedition 336 will provide a unique opportunity to access deep subsurface formation fluids from North Pond, including sampling from multiple depth horizons within oceanic crust. My goal is to develop quantitative polymerase chain reaction assays to determine the expression of functional genes in order to increase our understanding of microbial metabolisms in deep subsurface environments.