A team of researchers at the University of Massachusetts Amherst have discovered conductive properties in the microbial nanowires found in the bacterium Geobacter sulfurreducens that could revolutionize nanotechnology and bioelectronics.
The microbial filaments or nanowires in the bacterium allows electron transport across long distances -- thousands of times the bacterium’s length. This property was previously unknown to researchers. The biofilm, as it's called, can also move electron charges as efficiently as synthetic organic metallic nanostructures.
The discovery, reported in the Aug. 7th advance online issue of Nature Nanotechnology, could one day lead to the development of cheaper, nontoxic biosensors and solid state electronics that interface with biological systems.
Mark Tuominen, the lead physicist, says: "This discovery not only puts forward an important new principle in biology but in materials science. We can now investigate a range of new conducting nanomaterials that are living, naturally occurring, nontoxic, easier to produce and less costly than man-made. They may even allow us to use electronics in water and moist environments. It opens exciting opportunities for biological and energy applications that were not possible before."
In nature, the Geobacter species grows on iron minerals in soils and sediments and use their microbial nanowires to transfer electrons onto iron oxides, allowing them to "breathe". To better understand the biological process in the lab, the UMass researchers let Geobacter grow on electrodes and through studies found that the metallic-like conductivity in the biofilm could be attributed to a network of nanowires spreading throughout the biofilm.
Similar to the flexibility of artificial nano-wires, the conducting properties of the Geobacter biofilm could be manipulated by simply changing the temperature or regulating gene expression to create a new strain, for example. By adding a third electrode, the biofilm can act like a biological transistor, able to be switched on or off by applying a voltage.
Another advantage Geobacter offers is its ability to produce materials that are more eco-friendly and less expensive than man-made versions, many of which require rare elements, says the team.
Lead microbiologist Derek Lovley quips, "We’re basically making electronics out of vinegar. It can’t get much cheaper or more ‘green’ than that."