Living Biological Circuits Discovered

Until recently, the concept of electrical circuit has been considered to be an artificial one, with no direct equivalent in nature. In a new study of a bacteria species, this was proven to be wrong.

Colonies of the microorganism called Shewanella oneidensis display the same type of properties as electrical circuits, and they are able to form electrical networks by producing nanoscale wires.

These are structures resembling small hairs, which are capable of conducting electricity. Each bacteria in the colony produces them, and then the nanowires mingle together to form a grid.

Studies on the organism have not yet concluded, but experts say that the network is used to share energy between colony members, carry out collective breathing processes, or perhaps even for communications.

In a new set of experiments, researchers took colonies of these bacteria, and then placed them between microscopic electrodes, to see if the bacteria close the circuit.

Remarkably, the nanowires proved capable to close the circuit, allowing for a measurable current to flow through. These structures are made of proteins similar to the ones making up human hair.

“This is the first measurement of electron transport along biological nanowires produced by bacteria,” explains University of Southern California (USC) in Los Angeles biophysicist Mohamed El-Naggar.

Details of the impressive findings were published in the October 11 online issue of the esteemed journal Proceedings of the National Academy of Sciences (PNAS).

The experts say that Shewanella respires when it allows electrons to flow to metals, such as iron. When their access to such chemicals is restricted or cut out, they simply die off.

When subjected to adverse conditions, the bacterial cells start growing the nanowires, which can extend to find distant sources of electron acceptors. The grid then allows the entire colony to breathe.

“This would be basically a community response to transfer electrons. It would be a form of cooperative breathing,” El-Naggar argues.

According to the USC College Wrigley professor of geobiology Kenneth Nealson, using the nanowires to transport electrons from the colony to metals is the fastest way to accomplish respiration.

“You want the telegraph, you don't want smoke signals,” he concludes, quoted by LiveScience.