This Bacterium Can Survive on Electricity Alone

Scientists are hoping that a large battery in a South Dakotan gold mine could lure curious forms of bacteria that may help us understand what powers life as we know it.

That’s because scientists have begun to discover bacteria that live and thrive on electricity alone. Rather than mediating electrons through third-party materials (such as sugar or oxygen) like most organisms do, these bacteria transmit them unaccompanied by anything else. Understanding how these interactions work could give us a glimpse of the kind of life that might exist on other planets.

electric-bacteria
Geobacter sulfurreducens breathes by transferring electrons to iron oxides found in soil.

Here’s Catherine Brahic, writing for New Scientist:

Unlike any other living thing on Earth, electric bacteria use energy in its purest form—naked electricity in the shape of electrons harvested from rocks and metals. We already knew about two types, Shewanella and Geobacter. Now, biologists are showing that they can entice many more out of rocks and marine mud by tempting them with a bit of electrical juice. Experiments growing bacteria on battery electrodes demonstrate that these novel, mind-boggling forms of life are essentially eating and excreting electricity.

And scientists have found more than just a few new examples. Annette Rowe, a doctoral student at the University of Southern California, Los Angeles, has identified up to eight specimens demonstrating this behavior. That suggests to her advisor, Kenneth Nealson, that there could be a whole slew of organisms involved in direct extraction of electrons. 

While the immediate applications are obvious—for example, better biomachines (or self-powered devices) for human use—the findings could also tell us what life’s “bare minimum” is. In other words, at what amount of energy does life begin? And is it possible to create a bacterium that, through electric means, cannot be destroyed?

Brahic again:

For that we need the next stage of experiments, says Yuri Gorby, a microbiologist at the Rensselaer Polytechnic Institute in Troy, New York: bacteria should be grown not on a single electrode but between two. These bacteria would effectively eat electrons from one electrode, use them as a source of energy, and discard them on to the other electrode.

Other-worldly expeditions to mines or deep-sea caves could help us find more examples of organisms that interact with their environments this way, thereby bringing us closer to answering some of these questions.