This project aims to address one of potentially many novel metabolisms present in the deep biosphere of which little or nothing is known. Considering energy-yielding pathways, several studies focusing on Gibbs energy calculations and known geochemical parameters in other extreme environments have shown hundreds of potentially life supporting redox couples; while these reactions may not be favorable under standard conditions, the deep biosphere is anything but standard. As microbial life can eke out a living using metabolisms right at the edge of possibility, the potential for not only novel organisms, but geochemically relevant ones, is tremendous. Specifically, we will be looking at a zone present in a few deep sediment cores, first noted by Schrum et al. (2009) which exhibit ammonium loss in the absence of typical oxidants (i.e. no oxygen, no nitrite). Uptake for biomass production doesn’t appear feasible, either – hence the mystery. Using genetic and isotopic tools, we hope to figure out what organisms may be unique to these zones and investigate the feasibility, previously proposed, of ammonium oxidation coupled to sulfate reduction. Our main sample set includes cores from the Bay of Bengal, though similar features have also been noted off the east coast of the U.S.; potentially, processes such as this could be of global importance.