Collaborative Research: How bacteria control manganese(IV) oxide biomineralization using a multicopper oxidase complex

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With this award, the Chemistry of Life Processes Program in the Chemistry Division is funding Dr. Bradley Tebo from Oregon Health & Science University and Dr. Thomas Spiro from the University of Washington to find out how bacteria change dissolved manganese (Mn) into manganese oxide minerals. This chemical process produces manganese oxides that are widespread, highly reactive, efficient catalysts that play important roles in elemental biogeochemical cycles. Although these oxides are primarily made by microbial processes, the biological means for their formation are poorly understood. This project reveals the pathway of bacterial manganese oxide production, using the first purified active manganese-oxidizing enzyme complex. The project may uncover the biochemistry of how two processes-manganese oxidation and mineral formation-are achieved, laying the foundation for future application of biologically-derived manganese oxides in clean water technologies and energy storage and production. This project enhances the training of the next generation of scientists in interdisciplinary methods, and serves as a vehicle in outreach programs to engage undergraduate, middle, and high school students in studies of microbiology and biochemistry, as related to environmental science. In addition, postdoctoral fellows develop a Saturday Academy course targeting either 6-8 or 9-12 grade students and focusing on the importance of microbiology and biochemistry as related to environmental science. The Saturday Academy provides professional development for the postdoctoral fellow as the instructor.The project represents an investigation of how a purified protein can accomplish the difficult two-electron oxidation of Mn(II), forming a nanoparticulate MnO2 mineral product. Results to date indicate that the active protein belongs to the well-known multicopper oxidase family of enzymes, but with a unique ability to adapt the polynuclear chemistry of manganese to perform the catalysis. The research efforts are focused on establishing a molecular-level detailed mechanism of the catalysis, by resolving manganese oxidation intermediates and studying the effects of key mutations with an array of spectroscopic techniques. The spectroscopic studies are complemented by modeling, crystallography, and cryo-electron microscopy work to derive the 3D atomic structure of the enzyme. In the context of broader environmental applicability, the research explores the effect of other metals occurring in the environment on the enzymatic catalysis of manganese oxidation.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.