NSF-ANR: Cytochrome nanowires: secretion, assembly and function in ultrafast electron transfer by microbial biofilms

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Common soil bacterium Geobacter sulfurreducens has remarkable ability to form biofilms with high electronic conductivity rivalling those of synthetic polymers. This conductivity enables bacteria to transport respiratory electrons over hundreds of cell lengths to remote acceptors or partner cells. This process is critical for global environment and for applications in bioenergy, biofuels, and bioelectronics. It has been thought that biofilms transfer electrons via microbial nanowires made up of type IV pili filaments. The PI recently solved the first structure of a pilus from an organism capable of extracellular electron transfer (EET). These pili were thought to account for filament conductivity, but the work from the PI’s lab found that their conductivity is very low, in agreement with their structure. The aim of this project is to decipher the physical basis of nanowire secretion, assembly, and function. This project will characterize the G. sulfurreducens secretion machinery and the role of this novel class of bipartite pili. This project will identify the physical basis of pili -mediated cytochrome secretion and identify all factors essential for their biogenesis and develop tools to characterize the physical basis of nanowire secretion. This research will lead to a bioelectronic platform to manufacture pili required for the secretion of living biomaterials. This project will train users with different backgrounds in the use of multifunctional biomaterials to prepare the next generation of trans-disciplinary scientists trained at the interface of biology, physics, chemistry, data science and engineering.The primary aims of this project include reconstitution of G. sulfurreducens pili biogenesis, assembly, and secretion pathway in a heterologous system to dissect protein-protein interactions. Another aim is the elucidation of the mechanism of pilus dynamics and mechanical stability in the heterodimeric pilus assembly. The aims include determination of the mechanism of OmcS/Z secretion by quantifying how they interact with pili, and the characterization of the structure of the novel Geobacter pili-based cytochrome secretion system by cryo-electron tomography. This collaborative US/France project is supported by the US National Science Foundation and the French Agence Nationale de la Recherche, where NSF funds the US investigator and ANR funds the partners in France.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.