The primary objective of the proposed work is to demonstrate that the maximum entropy production principle is a solid foundation for understanding microbial biogeochemistry. This work addresses the need to have a better understanding of metabolic networks -- that is, metabolic pathways distributed across different microbial species, yet highly coordinated. In order to develop robust models of biogeochemistry, better understanding of the mechanisms that govern organization and function of distributed microbial metabolic networks is needed. Existing models of microbial biogeochemistry are reductionist, and adhere to the competitive exclusion principle which states that the species that grows the fastest will dominate. However, there are observations of syntrophy and cooperation in microbial communities that cannot be explained by this principle. Non-equilibrium thermodynamics may provide a more universal theory to explain such observations. This proposal seeks to develop a biogeochemical model based on the principles of maximum energy production (MEP), a principle in the realm of complexity theory. The MEP theory states that complex systems with many degrees of freedom will organize to a state of maximum entropy production. This work will lead to new theoretical advancements to describe microbial biogeochemistry. The approach is innovative in that it seeks to extend complexity theory to describe microbial community functioning. This is valuable because existing reductionist models fail in robustness and predictive power. A strength of the model is that the new theory will be tested using a field site for PRB. The investigator has written a solid proposal it is well written, comprehensive in coverage of appropriate literature, and has the right balance of detail and breadth. Broader impacts are achieved through meaningful undergraduate research and educational experiences.
