Scientists have found that the hair-like nanoscale filaments on some bacteria have electrical conductivity comparable to that of copper, an advance that may lead to low-cost, non-toxic, biological components for light-weight electronics.
Although proteins are usually electrically insulating, hair-like nanoscale filaments (called pili) on the surface of Geobacter bacteria were found to exhibit metallic-like conductivity. To understand why pili are conductive, scientists from the University of Massachusetts and Brookhaven National Laboratory in the US used X-ray diffraction to analyse the structure of the filaments.
They found that the electronic arrangement and the small molecular separation distances (about 0.3 nanometres) give the pili an electrical conductivity comparable to that of copper. Enhancing pili’s electrical conductivity through genetic engineering could be used to construct low-cost, non-toxic, nanoscale, biological sources of electricity for light-weight electronics and for bioremediation, researchers said.
Researchers examined the pili with synchrotron X-ray microdiffraction and rocking-curve X-ray diffraction.
The experimental results support the concept that the pili of a bacteria known as G sulfurreducens represent a novel class of electronically functional proteins in which aromatic amino acids promote long-distance electron transport. In other words, they are able to conduct electricity.
The mechanism for long-range electron transport along the conductive pili of G sulfurreducens is of interest because these “microbial nanowires” are important in biogeochemical cycling as well as applications in bioenergy and bioelectronics.