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Title: Structural Basis for Metallic-Like Conductivity in Microbial Nanowires

Direct measurement of multiple physical properties of Geobacter sulfurreducens pili have demonstrated that they possess metallic-like conductivity, but several studies have suggested that metallic-like conductivity is unlikely based on the structures of the G. sulfurreducens pilus predicted from homology models. In order to further evaluate this discrepancy, pili were examined with synchrotron X-ray microdiffraction and rocking-curve X-ray diffraction. Both techniques revealed a periodic 3.2-Å spacing in conductive, wild-type G. sulfurreducens pili that was missing in the nonconductive pili of strain Aro5, which lack key aromatic acids required for conductivity. The intensity of the 3.2-Å peak increased 100-fold when the pH was shifted from 10.5 to 2, corresponding with a previously reported 100-fold increase in pilus conductivity with this pH change. These results suggest a clear structure-function correlation for metallic-like conductivity that can be attributed to overlapping π-orbitals of aromatic amino acids. A homology model of the G. sulfurreducens pilus was constructed with a Pseudomonas aeruginosa pilus model as a template as an alternative to previous models, which were based on a Neisseria gonorrhoeae pilus structure. This alternative model predicted that aromatic amino acids in G. sulfurreducens pili are packed within 3 to 4 Å, consistent with the experimental results. Thus,more » the predictions of homology modeling are highly sensitive to assumptions inherent in the model construction. Finally, the experimental results reported here further support the concept that the pili of G. sulfurreducens represent a novel class of electronically functional proteins in which aromatic amino acids promote long-distance electron transport.« less
 [1] ;  [2] ;  [3] ;  [3] ;  [4] ;  [5] ;  [3] ;  [6] ;  [3]
  1. Univ. of Massachusetts, Amherst, MA (United States). Dept. of Physics; Univ. of Massachusetts, Amherst, MA (United States). Dept. of Microbiology
  2. Univ. of Massachusetts, Amherst, MA (United States). Dept. of Microbiology; College of the Holy Cross Worcester, MA (United States). Dept. of Biology
  3. Univ. of Massachusetts, Amherst, MA (United States). Dept. of Microbiology
  4. Brookhaven National Lab. (BNL), Upton, NY (United States). Photon Sciences Directorate
  5. Brookhaven National Lab. (BNL), Upton, NY (United States). Center for Functional Nanomaterials (CFN)
  6. Univ. of Massachusetts, Amherst, MA (United States). Dept. of Physics
Publication Date:
OSTI Identifier:
Grant/Contract Number:
AC02-98CH10886; N00014-13-1-0550; N00014-12-1-0229
Accepted Manuscript
Journal Name:
mBio (Online)
Additional Journal Information:
Journal Name: mBio (Online); Journal Volume: 6; Journal Issue: 2; Journal ID: ISSN 2150-7511
American Society for Microbiology
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States