Scientists from the University of Massachusetts at Amherst, Holy Cross, and Brookhaven National Laboratory have discovered that the filaments present in the surface of Geobacter bacteria have conductive properties comparable to those of copper. The finding, published in the journal mBio, could accelerate the introduction of biological material in nanoscale electronical devices.
In general, proteins are electrical insulators. But when the teams of Dmytro Nykypanchuk and Derek R. Lovley analyzed the physical properties of Geobacter sulfurreducens pili, they discovered that they conduct electricity like a metal. Pili are bacterial appendages composed of proteins, with a role in bacterial conjugation. Some available homology models for G. sulfurreducens pili suggested that the pilus structure was not the reason for its conductivity. Suspecting that the opposite was true, Nykypanchuk and Lovley decided to examine the bacterial hair structure with synchrotron X-ray microdiffraction and rocking-curve X-ray diffraction.
Electronic arrangement and small molecular separation distances
The researchers found that G. sulfurreducens pili have a periodic 0.32 nm spacing that is absent in the pili from Aro5, a strain whose pili are nonconductive. The scientists concluded that Aro5’s pili lack key aromatic amino acids for conductivity. These results present a clear correlation between pili structure and conductivity, which can be ultimately attributed to overlapping orbitals of aromatic amino acids.
The conductive properties of bacterial pili are important in biogeochemical cycling, and could find applications in bioenergy and bioelectronics. Genetic engineering of bacteria could enhance the conductivity of pili, making them a more attractive construction material for nanoscale electronics.
Source: U.S. Department of Energy