Bacterial Live Wires

Investigators from the Pacific Northwest National Laboratory have demonstrated that some bacterial organisms keep themselves busy by making tiny nanowires, used for distribution of energy among individuals.

When Yuri Gorby discovered that a microbe which transforms toxic metals can sprout tiny electrically conductive wires from its cell membrane, he reasoned this anatomical oddity and its metal-changing physiology must be related.
A colleague who had heard Gorby’s presentation at a scientific meeting later reported that he, too, was able to coax nanowires from another so-called metal-reducing bacteria species and further suggested the wires, called pili, could be used to bioengineer electrical devices.
It now turns out that not only are the wires and their ability to alter metal connected-but that many other bacteria, including species involved in fermentation and photosynthesis, can also form wires under a variety of environmental conditions.
“Earth appears to be hard-wired,” said Gorby, staff scientist at the Department of Energy’s Pacific Northwest National Laboratory, who documents the seeming ubiquity of electrically conductive microbial life in the July 10 advance online Proceedings of the National Academy of Sciences.
In a series of experiments, Gorby and colleagues induced nanowires in a variety of bacteria and demonstrated that they were electrically conductive. The bacterial nanowires were as small as 10 nanometers in diameter and formed bundles as wide as 150 nanometers. They grew to be tens of microns to hundreds of microns long.
The common thread involved depriving a microbe of something it needed to shed excess energy in the form of electrons. For example, Shewanella, of interest in environmental cleanup for its ability to hasten the weathering of toxic metals into benign ones, requires oxygen or other electron acceptors for respiration, whereas Synechocystis, a cyanobacterium, combines electrons with carbon dioxide during photosynthesis.
Bereft of these “electron acceptors,” bacterial nanowires “will literally reach out and connect cells from one to another to form an electrically integrated community,” Gorby said.
“The physiological and ecological implications for these interactions are not currently known,” he said, “but the effect is suggestive of a highly organized form of energy distribution among members of the oldest and most sustainable life forms on the planet.”

With a growing possibility that future medical gadgets will be based on nanowires, this kind of research is always exciting to see.
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