Microbial Nanowires Exhibit Metal-like Conductivity
Recent reports indicate that common anaerobic subsurface microbes respire metal-containing minerals and radionuclide contaminants via appendages, known as “nanowires,” on their cell surface. These nanowires facilitate electron transport from central metabolism inside the cell to electron acceptors on the outside of the cell. New results from a DOE team led by the University of Massachusetts show that microbial pili composed of natural proteins exhibit metal-like conductivity in the absence of cytochromes and function as “nanowires,” a finding that could have far-reaching biotechnological and bioelectronic implications. Researchers have shown that they could manipulate biofilms grown in microbial fuel cells, “tuning” electrical conductance depending on the expression of specific genes associated with pili (“nanowire”) production. Furthermore, X-ray diffraction and electrical studies of purified “nanowire” filaments attribute the electron-conducting behavior to the molecular structure of the pili that results in close alignment of aromatic groups within the amino acid components facilitating p-orbital overlap and charge delocalization. The data help to explain how these microorganisms respire solid minerals and radionuclide contaminants in anaerobic subsurface environments and has far-reaching implications for nanomaterial biodesign and biotechnology.
Malvankar, N. S., M. Vargas, K. P. Nevin, A. E. Franks, C. Leang, B. Kim, K. Inoue, T. Mester, S. F. Covalla, J. P. Johnson, V. M. Rotello, M. T. Tuominen, and D. R. Lovley. 2011. “Tunable Metallic-Like Conductivity in Microbial Nanowire Networks,” Nature Nanotechnology, DOI: 10.1038/NNANO.2011.119.