Scientists at the University of Massachusetts at Amherst, sponsored by the Office of Naval Research (ONR) have genetically modified common soil bacteria to produce nanowires. These nanowires have metallic-like conductivity. In fact, the scientists working on this research themselves were surprised at the conductivity of the wires. These are having a diameter of 1.5 nanometers (roughly 60,000 times thinner than a human hair). There has been a very hot debate lately amongst the scientists from across the globe, whether microbial nanowires, produced from the specialized electrical pili of the mud-dwelling anaerobic bacterium Geobacter sulfurreducens, truly have metallic-like conductivity as claimed by the discoverers.
The researchers of Massachusetts Amherst, led by microbiologist Dr. Derek Lovley, and postdoctoral researcher Mr. Nikhil Malvankar with their colleagues say, “We have settled the dispute between theoretical and experimental scientists by devising a combination of new experiments and better theoretical modelling. We have engineered wires that can be produced using renewable “green” energy resources like solar energy, carbon dioxide or plant waste; are made of non-toxic, natural proteins; and avoid harsh chemical processes typically used to create nanoelectronic materials.”
Today the electronic devices practically touch all facets of common man’s life. And it has a big unending appetite for a technology that is smaller, faster, mobile and powerful. Scientists and electronic devices manufacturers are trying to meet this ever growing demand with the advances in nanotechnology (manipulating matter on an atomic or molecular scale). This discovery of nanowires is surely going to be very handy in complying the requirements electronic devices.
The researchers used Geobacter bacteria in their experiments. They possess nanoscale protein filaments which extend outward from their bodies. These protein filaments are the ones which help these bacteria’s growth, as they allow it to make electrical connections to the iron oxide contained in the soil where it lives, allowing the Geobacter to survive. It was always believed for decades that Geobacter could never be made to conduct electricity so that it could ever be of any use for human interests, in the field of electronics. These scientists altered the bacteria’s genetic makeup to get the bacteria to perform this task, by replacing two of its amino acids with tryptophan, which is remarkably good at transporting electrons at the nanoscale, and thus discovered nanowires.
Dr. Derek Lovley while explaining the research says, “In Nikhil’s experiments, we see a clear signature of the close packing of the aromatic amino acids. Non-conductive pili lack this. Also, when Nikhil acidified the pili, there was an increase in the packing of the aromatics in proportion to an increase in their conductivity. These results are consistent with our concept of metallic-like conductivity in the pili. None of the models that rejected our hypothesis were consistent with these results.”