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.