The reason we’re hooked on oil, and its climate warming derivatives, is the astonishing amount of energy packed into every gallon of the stuff. Gasoline burns brighter compared to alternatives from ethanol to electricity whenever it’s stored in a tank or battery. But if we could make energy-dense liquids from electrons, the energetic sub-atomic particles driving an electrical current, we could begin weaning ourselves off fossil fuels, particularly in transportation.
Mariprofundus ferrooxydans PV-1, a little bacteria from the ocean, may be the microbe for the job. It feasts on the iron atoms dissolved in seawater, which makes it attractive to scientists who want to turn it into an electric factory for making biofuels. Here’s how it works: Most life on Earth depends on the sun to drive photosynthesis. Plants use solar radiation to use and capture chemical energy, combining water and carbon dioxide to create sugars, carbohydrates, proteins, and other compounds. These are in turn eaten by other organisms higher up the food chain. A few rare classes of organisms actually feed directly on the energy in chemical bonds of the Earth’s minerals. By rearranging molecules, the microbes grab energy from the transfer of electrons among atoms. One group, known as lithoautotrophs, or "eaters of rock," reduce mineral compounds to fuel their metabolism while driving massive geological processes such as rock weathering in the process.
M. ferrooxydans is one of them. Iron is its main course, and primary source of electrons. So researchers at the University of Minnesota, Twin Cities, publishing in the open-source journal mBio, isolated the bacteria and trained them to "eat" electrons in an electric current flowing from a cathode. Despite the lack of iron atoms, the bacteria thrived, growing as a biofilm on the electrode. The results, say the researchers, suggest similar organisms may one day turn an electrical current into a rich source of organic compounds for biofuels. This study, and a handful of others like it, at least show it’s possible to shoot electrons into a bacteria’s metabolism and produce organic compounds as well.
But there’s a long way to go. The next step (PDF) is to harness renewable, carbon-free electricity that serves as a food supply for electron-eating bacteria to churn out biofuels. Research to achieve that vision is only just beginning.