The overarching goal and the intellectual merit of this project is to describe and understand the microbial composition, structure, and metabolic underpinnings of hydrogen metabolism in the Yellowstone geothermal ecosystem. The Yellowstone geothermal ecosystem is generally considered to be supported by sulfur metabolism. However, recent work suggests that communities instead are dependent on hydrogen-metabolism and may dominate this and other geothermal ecosystems. Hydrogen is the most abundant element in the universe and the basis of diverse microbial energy metabolisms throughout the bacterial and archaeal phylogenetic domains. This wide phylogenetic occurrence suggests that hydrogen metabolism arose early in the evolution of life. Although ubiquitous and ancient, little is known about the presence/absence of the enzymes responsible for this metabolism (hydrogenase enzymes) in naturally occurring microbial communities that are supported by hydrogen as a primary energy source. The proposed work will focus on polymerase chain reaction (PCR) amplification of environmentally obtained DNA samples to characterize and classify the occurrence of the functional genes responsible for iron, iron/iron, and iron/nickel hydrogenase enzymes. Several samples will be collected around Yellowstone National Park and subjected to analysis in the lab.
The broader scientific impact of the proposed work is at least two fold. First, if hydrogen is indeed the main fuel for life above the photosynthetic limit of 72 degrees centigrade, why is this? Is it an evolutionary root of life, for example? Second, how widespread is the ability to use molecular hydrogen as an electron donor, and what enzymes are responsible for that utilization? The answer to these questions has relevance not only for a greater understanding of high-temperature ecosystems, but how these processes can be harnessed for alternative fuel delivery through an enhanced understanding of hydrogen utilization and/or generation. In addition, the hydrogenase functional gene analysis of the Yellowstone ecosystem, will provide new perspectives on potential chemistries of life. The overall results will be relevant to geomicrobiology, high-temperature microbiology, evolution, applied science and to the emerging field of astrobiology. The project will include graduate student training opportunities. Other educational and outreach activities will be coordinated with the Yellowstone Center for Resources.
