Scientists sponsored by US Navy genetically modify soil bacteria to conduct electricity
Scientists sponsored by the Office of Naval Research (ONR) have genetically modified a common soil bacterium to create electrical wires that not only conduct electricity, but are thousands of times thinner than a human hair.
As electronic devices increasingly touch all facets of people’s lives, there is growing appetite for technology that is smaller, faster and more mobile and powerful than ever before. Thanks to advances in nanotechnology, industry can manufacture materials only billionths of a meter in thickness.
“Research like Dr. Lovley’s could lead to the development of new electronic materials to meet the increasing demand for smaller, more powerful computing devices,” said Linda Chrisey, a program officer in ONR’s Warfighter Performance Department, in a press release.
“Being able to produce extremely thin wires with sustainable materials has enormous potential application as components of electronic devices such as sensors, transistors and capacitors.”
The bacteria that Lovley has used in his experiments are called Geobacters; they possess nanoscale protein filaments extending outward from their bodies. These protein filaments are the key to the bacteria’s growth, as they allow it to make electrical connections to the iron oxide contained
in the soil where it lives. While these connections allow the Geobacter to survive, it was believed that they could never be made to conduct electricity to the extent that it would ever be useful for human interests, namely electronics.To get the bacteria to perform that task, Lovley altered the bacteria’s genetic makeup by replacing two of its amino acids with tryptophan, the chemical in turkey that supposedly makes us sleepy. Whether tryptophan actually makes us sleepy or not, it is remarkably good at transporting electrons at the nanoscale.
“As we learned more about how the microbial nanowires worked, we realized it might be possible to improve on nature’s design,” said Lovley. “We rearranged the amino acids to produce a synthetic nanowire that we thought might be more conductive. We hoped that Geobacter might still form nanowires and double their conductivity.”
In the latest research, described in the journal Small, Lovley and his colleagues were able to get these bacteria nanowires to perform beyond all expectations. The genetically modified bacteria were over 2,000 times as conductive as they were in their natural state. With the greater conductivity came two other new properties: greater durability and smaller size (the filaments’ diameters shrank to as little as 1.5 nanometers).
While applications for the bacteria-based nanowires could be as far ranging as digital electronics and medical sensors, the research was supported by the ONR, so military applications are likely going to be high on the priority list.
From a military perspective, the nanowires could feed electrical currents to specially engineered microbes to create butanol, an alternative fuel. This would be particularly useful in remote locations like Afghanistan, where fuel convoys are often attacked and it costs hundreds of dollars per gallon to ship fuel to warfighters.
Also, these nanowires could provide electricity to microbes that are placed on silicon chips and are used to detect chemicals, such as explosive materials. “This is an exciting time to be on the cutting edge of creating new types of electronics materials. The fact that we can do this with sustainable, renewable materials makes it even more rewarding,” Lovely added.
