ETBC: Organic Geochemical Transformations and the Deep Biosphere -- Identifying the Food Sources for Microbes in Sedimentary Systems

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Intellectual Merit: This research explores how geochemical processes support microbes living deep in the Earth. A major challenge in understanding how life can survive at depth is the identity and source of organic compounds that are consumed by microbes. While some of these compounds are likely to be produced by other subsurface microbes, this works focuses on the large inventory of consumable organic compounds that comes from geochemical transformations of organic matter that take place as sediments are buried and exposed to elevated temperatures and pressures. Goals of the work are to examine, both theoretically and experimentally, chemical reactions that occur at temperatures and pressures greater than microbial life can withstand. These high temperature and pressure reactions produce organic solutes that are transported upward into the inhabited zones of the subsurface. The primary focus of the research is to determine how reactions between hot water and organic matter generate small organic compounds that ultimately feed the deep biosphere. Phase I focuses on hydrothermal experiments of well-known reactions that transform simple hydrocarbons into alcohols, ketones, and carboxylic acids at elevated temperatures and pressures. Phase II explores these same reactions, but in the context of a more realistic and thus complex geologic system that includes the clay minerals found in all organic rich sediments and sedimentary rocks. Most of these reactions have not been systematically studied under geologically realistic conditions. As a result, our present understanding of these transformation mechanisms in nature are speculative. This work produces rigorous results from which calculations can be made to predict the microbial metabolic potential of areas deep within the Earth?s crust. Broader Impacts: This work provides organic chemists with new methods to control reactions and provides geochemists with new predictive, mechanistic models of organic matter transformations. New models will inform those making site selections for future ocean and continental drilling efforts that explore the deep biosphere and will allow us to better understand the generation of petroleum. This project also provides a means to predict where prospecting of new microbial species with unusual properties can be found. The hydrothermal reactor approach may also provide green alternatives to incineration or burial of organic waste. In terms of education and training, the work supports post-docs, graduate students, and undergraduates, and supports PIs whose gender is under-represented in the sciences. Public outreach will include development new materials for the ?I?m College Bound? program. Graduate and undergraduate researchers associated with this project will help develop new geo/earth science demonstrations and coordinate student volunteers. The demonstrations, assignments and lesson plans will be disseminated and published on the "I'm College Bound" web site.