Understanding and using microbial conductive nanowires

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Abstract Long-range (>10 μm) transport of electrons along networks of G. sulfurreducens protein filaments, known as microbial nanowires, has been invoked to explain a wide range of globally important redox phenomena. The remarkable electronic conduction capability of those nanowires has sparked a great deal of interest in the medical application space, such as for building biocompatible materials and biosensor. For more than a decade, G. sulfurreducens nanowires were thought to be bacterial type IV pili, supported by many indirect genetic and biochemical observations. Recently we showed that these conductive nanowires are not made of type IV pilins. Instead, these structures are a polymerized multi-heme c-type cytochrome, OmcS, which have never been characterized before. The OmcS filament model is consistent with the known roles of OmcS in Geobacter respiration, but our knowledge of cytochrome appendages is still very limited. This study aims at addressing fundamental scientific questions about cytochrome filaments in respiring prokaryotes as well as applying our discoveries into the general medical field. Specifically, I will: A) identify and characterize novel cytochrome filaments in bacterial and archaeal strains, through bioinformatics algorithms followed by microscopic validation. B) Then I will study the conduction mechanism of these filaments by high resolution cryogenic electron microscopy (cryo-EM) and conductivity measurement. C) Finally, based on these new insights into cytochrome filaments, I will create a novel design for a self-assembled conductive nanowire. These nanowires may be derived directly from a novel cytochrome filament or may contain a peptide/protein based self-assembled scaffold core with soluble cytochromes appended to the outer surface. The results will advance our understanding of cytochrome nanowires, as well as generating self-assembling nanowire scaffolds that may be used in many future biomedical applications.