In the extreme world of bacteria, stunts such as living in hot springs or without oxygen are, like, totally unimpressive. But then there are bacteria that live off electricity, feeding directly on naked electrons. Even more surprisingly, scientists are finding that these bacteria are not even that rare.
"Stick an electrode in the ground, pump electrons down it, and they will come," begins a fascinating New Scientist piece on these electricity-eating microbes. For a while now, we've known about two types of bacteria that eat electricity, Shewanella and Geobacter. As scientists stick their electrodes in wells and marine mud and gold mines—not unlike fishing with a baited hook—they've found several more types of electricity-eating bacteria.
What's so surprising about all this is that free electrons are dangerous. Bacteria that eat electricity are like humans who "power up by shoving our fingers in a DC electrical socket," one researcher tells New Scientist. These bacteria are getting energy in its purest form as electrons. The rest of us—by which I mean the rest of all known life on Earth—also move electrons around for energy, but the process is managed through a complex set of reactions involving a molecule called ATP. You may have vague recollections about it from high school biology; it's really, really complicated. It's also how we keep our cells from being torn apart by free electrons. How these electric bacteria manage it is still a mystery.
In the wild, the bacteria scavenge free electrons from rocks and sand. In the lab, Kenneth Nealson of the University of Southern California is trying to grow them directly on electrodes. Growing electric bacteria raises the intriguing possibility of putting them to use. Researchers have found that "tens of thousands of electric bacteria can join together form daisy chains that carry electrons"—essentially a fully living (and live) electrical biocable. [New Scientist]