Combining geochemical data with microbial ecological data makes it possible to predict the distribution of microbial populations and the processes that they catalyze in nature. In this research we will focus on the contrasting microbial processes of methane production (e.g., methanogenesis) and methane consumption (e.g., methanotrophy) as a framework for evaluating the linkages between geochemical predictions and the distribution, diversity, and activity of organisms that catalyze these processes. The overarching rationale for targeting these biological processes is that the combined activities of methanogenesis and methanotrophy largely control the flux of the potent greenhouse gas methane to our atmosphere, the extent of which may significantly impact global climate. Defining the constraints on the distribution of microbial populations catalyzing these two processes in nature can significantly advance our understanding of the impact that a perturbation to their environment would have on their respective activities and the consequence that this may have on the global carbon cycle. Existing geochemical predictions from hydrothermal ecosystems in Yellowstone National Park, Wyoming indicate that the occurrence of populations catalyzing methane production should be highly proscribed, but that aerobic and anaerobic methanotrophy should be widespread and that populations engaged in these activities should display significant genetic diversity as a function of the spring fluid composition. The thermodynamic predictions will be used to guide experiments aimed to interpret data on the distribution of methanogens and methanotrophs and their respective activities. The integration of geochemical data and biological data will be achieved using newly developed ecological modeling tools. These models will provide a more comprehensive understanding of the extent to which the distribution, diversity, and activity of functional groups of microorganisms reflect the physical and chemical characteristics of their environment. Defining the extent to which such relationships exist using this framework has critical implications for our understanding of the constraints which led to extant biodiversity and will enable predictions of how changes in environmental conditions will affect the functioning of those microbial ecosystems. This unified research goal will engage students in hands on interdisciplinary research where they will merge the traditionally independent disciplines of geochemistry and microbial ecology. This goal will be met through the coordination of geochemical and microbiological analyses in field research settings as well as through coordinated laboratory experimentation at both Arizona State University and Montana State University. In addition, workshops will be held with the specific focus of training students in merging knowledge from these disciplines. Given this exciting area of scientific exploration and discovery, the proposed work will also result in several tangible opportunities for education and outreach, most of which are built on our previous experience and commitment to educational programs for various audiences. This includes field-and classroom-based efforts aimed at advancing scientific knowledge to other sectors of the public including K-12 students, undergraduate and graduate students, and high school and community college educators. This project also will help promote research on the geochemistry, energetics, and microbial ecology of terrestrial hot springs and active serpentinizing systems through networking among scientists worldwide.