Dynamics of carbon and energy fluxes in methanogenic archaea

About This Grant

This project will identify and characterize spatially coupled biochemical processes in methanogenic archaea, microbes that have the unique capability to grow by synthesizing the high-energy fuel methane. 60-99% of the carbon that methanogenic archaea consume is converted to methane gas that can be used to produce heat, electricity, transportation or rocket fuel with clean water as a byproduct. Molecular, biochemical, and computational techniques will be used to investigate how enzymes used by methanogenic archaea work together to efficiently convert low-energy growth substrates to high-energy methane gas. By identifying and characterizing enzyme interactions within cells, the research will reveal how methanogenic archaea control the flow of carbon and electrons to convert abundant, low-energy substrates such as acetate and methanol into methane gas. This knowledge will lead to a better understanding of how methanogenic archaea function in a variety of natural environments, such as in marine, freshwater, and terrestrial subsurface or in human and animal digestive tracts. This work generates knowledge with translational potential that could be used to increase the supply of renewable methane fuel to meet society’s energy needs. This project also supports recruitment and education of undergraduate, graduate, and postdoctoral trainees in anaerobic microbial physiology, molecular biology, and redox biochemistry in preparation for careers in industry, academia, and government to support US bioindustries. Methanogenic archaea (methanogens) have evolved to thrive near the “thermodynamic limit of life” in that they obtain less than 1 mole ATP per mole substrate consumed. The extreme thermodynamic constraint faced by methanogens requires a high degree of metabolic efficiency compared to heterotrophic organisms such as E. coli that obtain more than 36 ATP per mole of glucose substrate. Because of the ancient evolutionary origin of methanogenesis enzymes (predating the Last Unified Common Ancestor, LUCA), determining if and how Wood-Ljungdahl pathway and Wolfe Cycle methanogenesis enzymes interact could shed light on biochemical strategies that have evolved to optimize metabolic efficiency in methanogens and other microbes. Previous work has shown that enzymes in these two pathways form a multi-enzyme complex in the methanogen Methanosarcina acetivorans. It is proposed that highly conserved enzymes such as those in the Wolfe Cycle and Wood-Ljungdahl pathway may have evolved to form large multienzyme complexes resulting in low spatial, kinetic, and chemical entropy that enables highly efficient growth on low-energy substrates. Specifically, the project will test the hypothesis that methanogenic growth kinetics of M. acetivorans are dependent on substrate-specific composition and stoichiometry of multi-enzyme complexes that physically couple the terminal oxidoreductase with carbon-dioxide-fixation enzymes. Molecular, biochemical, and computational techniques, including cryoEM, will be used to detect, characterize, and model methanogenesis enzyme complexes in M. acetivorans. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.