New research into electricity-conducting bacteria could lead to environmentally friendly "bio-batteries" that could create energy, be used as factories for biological products, or clean out heavy metals from contaminated soils.
Researchers at the University of East Anglia in the U.K., and the Pacific Northwest National Laboratory in Washington, discovered how a special type of bacteria known as Shewanella oneidensis, conducts an electrical charge when it's around heavy metals.
These bacteria live off iron and heavy metals, similar to how we live off of oxygen. They use it to make energy the way we use oxygen and food to make the energy that runs our bodies.
Understanding how they do this could help us use them to clean up soil contamination, trap carbon dioxide, or even make batteries that use inspiration from the microbial world to produce energy.
These bio-based batteries are cleaner than traditional batteries and would be able to recharge themselves. The energy they create would be renewable, non-flammable, and non-toxic. In this case, the bacteria would be exposed to heavy metals, then create energy from this interaction.
This marine bacteria lives in rivers and seas throughout the world — everywhere from the Amazon to the Baltic Sea. When it comes into contact with heavy metals like iron and manganese, it can make electricity by shuttling tiny particles called electrons across their outer membranes.
The researchers didn't know what proteins they were using to move these electrons. Knowing how this happens in nature can help inspire better battery design.
"We knew that bacteria can transfer electricity into metals and minerals, and that the interaction depends on special proteins on the surface of the bacteria. But it has not been clear whether these proteins do this directly or indirectly though an unknown mediator in the environment," study researcher Tom Clarke, of the University of East Anglia, said in a press release.
So, they decided to build a "fake" or synthetic version of the bacteria in the lab using only the proteins they believed were the most important in the electricity-conducting trait. They used this model to see how the bacteria created the charge. They found that proteins on the bacteria interact with minerals containing iron, change them, and generate a charge.
"Our research shows that these proteins can directly 'touch' the mineral surface and produce an electric current, meaning that it's possible for the bacteria to lie on the surface of a metal or mineral and conduct electricity through their cell membranes," Clarke said.
In the future, scientists could harness the mechanism the bacteria use, co-opting it for our own use as a power source in inaccessible or hostile environments.
"Bio batteries in the future will be extremely useful in dark environments where there is no solar power because they can work continuously in remote areas after earthquakes or at the bottom of the ocean, for instance,"Clarke told The Daily Mail.
"We may also see them being used for everyday gadgets, such as mobile phone chargers or cars," in "microbial fuel cells"— a biologically-based energy producing system — within 10 years.
"These bacteria show great potential as microbial fuel cells, where electricity can be generated from the breakdown of domestic or agricultural waste products," Clarke said. "Another possibility is to use these bacteria as miniature factories on the surface of an electrode, where chemical reactions take place inside the cell using electrical power supplied by the electrode through these proteins."
The study was published in the March 25 issue of the journal Proceedings of the National Academy of Sciences.