The discovery that microbial nanowires inside the bacterium Geobacter sufurreducens can conduct electricity not only represents a paradigm shift in our fundamental understanding of biology but also could completely change how we manufacture and use electronics.
Researchers at the University of Massachusetts, led by microbiologist Derek Lovley with physicists Mark Tuominen and Nikhil Malvankar, have discovered that the Geobacter bacterium uses the nanowire-like protein filaments to transfer electrons into iron oxide (rust) contained within the soil where they live, and that this mechanism serves the same function as oxygen does for humans.
While the research, which was published in the August 7th advanced online edition of Nature Nanotechnology, represents the first time that metallic-like conduction of electrical charge has been observed in a protein filament, the researchers had conjectured as far back as 2005 that this was the case.
Because they didn’t have the mechanism to demonstrate this capability, their hypothesis was met with a fair amount of skepticism. It was believed that if such conduction occurred, it had to involve a mechanism that used a series of proteins known as cytochromes.
The researchers were able to continue their research in a fairly simple way by allowing the Geobacter to grow on electrodes, where the bacteria produce a electrically conductive biofilms. The researchers were able to use a series of genetically modified strains of the bacterium to narrow down the source of the metallic-like electrical conductivity inside the biofilm to a network of nanowires within the bacterium.
"This discovery not only puts forward an important new principle in biology but in materials science,” says Mark Tuominen in the U Mass press release. “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."While Lovley (the microbiologist) has been working with the Geobacter bacterium now for nearly two decades in everything from bioremediation to the synthesis of biofuels (see video below), it was the addition of the physicists to the research that could make this a significant breakthrough in electronic materials research.
“As someone who studies materials, I see the nanowires in this biofilm as a new material, one that just happens to be made by nature, says Tuominen. “It’s exciting that it might bridge the gap between solid-state electronics and biological systems. It is biocompatible in a way we haven’t seen before."While mobile phones that you can use while scuba diving may be a long way off, this would seem to be an inexpensive way to replace nanowires made from toxic and expensive materials in everything from biosensors to solid-state electronics that are used in connection with biological systems.
Dexter Johnson is a contributing editor at IEEE Spectrum, with a focus on nanotechnology.