ABSTRACT

Intellectual Merit: The primary objective of this proposal is to develop a new rate law for the kinetics of microbial metabolisms in geological environments. The new rate law will advance the study of geobiology and biogeochemistry by accounting for how available energy and microbial diversity control the progress of microbial metabolisms in geological environments.
Investigators will develop the new rate law based on: (1) a theoretical model for thermodynamic control of microbial metabolisms; (2) limits to microbial kinetic parameters derived from collision theory and the minimum requirements for microbial growth; and (3) the diversity and abundance of microbial taxonomic groups in the environment. These three bases of the new rate law lead to three primary research tasks: (1) quantifying the significance of thermodynamic control on microbial metabolisms in geological environments; (2) developing a theoretical approach that integrates microbial diversity into kinetic rate laws; and (3) comparing the performance of the new model to traditional kinetic models (i.e., the Monod equation) by comparing the output of both models to in situ rates of methanogenesis as a test case.

They will develop the new rate law and apply it to predicting the seasonal rates of methanogenesis in the sediments of Upper Klamath Lake in southcentral Oregon. Their preliminary results demonstrate modest methanogen diversity but significant rates of methanogenesis. Seasonal variation in organic matter loading into these sediments leads to a wide range in electron donor concentrations, offering a natural experiment for developing our new theory of geomicrobial kinetics.

The new rate law developed in this proposal accounts for two critical, yet largely neglected, controlling factors on biogeochemical processes in the environment, i.e., the availability of chemical energy and the diversity of microorganisms. The new rate law therefore bridges the gap between empirical rate laws (e.g., the Monod equation) applicable for pure-cultures under energy-rich conditions and the kinetics of diverse microorganisms in geological environments. The new theory integrates geochemistry and microbial diversity into geomicrobial kinetics and, therefore, advances ongoing research efforts that seek to understand geological environments as habitats for diverse microorganisms. The new theory can be applied to the prediction of microbial activities in both natural environments and polluted areas, or in remote sites where direct sampling is not feasible.

Broader Impacts: The proposed research addresses a compelling question in geobiology and biogeochemistry − how to predict the activities of diverse microorganisms in geological environments?

Investigators will use our multidisciplinary approach to provide learning opportunities at all levels from K-12 to postgraduate. They will collaborate with science instructors at a high school near the field site to develop a sustainable and replicable classroom unit on the kinetics of methanogenesis and the carbon cycle. This unit will be inquiry-based and will introduce students to environmental science via a series of hands-on field and laboratory experiences centered on a common theme ? the cycling of carbon in Oregon lakes. The unit will be distributed to all Oregon K-12 educators, and it will be designed to meet a new requirement of the Oregon State Board of Education for additional inquiry-based science instruction in Oregon public schools. The proposed project will support two Ph.D. students. PIs will also recruit three to four undergraduate students into our research program via the support of the NSF-funded Undergraduate Catalytic Outreach and Research Experiences program and the Summer Program for Undergraduate Research at the University of Oregon.

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