In a new study, iron-oxidizing microbes give fresh meaning to the phrase "living off the grid," and provide fresh hope as a potential biofuel.
Researchers at the University of Minnesota, St. Paul, have coaxed a species of bacteria into trading their usual diet of partially-oxidized iron for a small current of electricity--a trick that may eventually make the microorganisms useful producers of biofuels.
The bacterium involved in the study was Mariprofundus ferrooxydans, a species that makes its home around hydrothermal vents on the seafloor. Like other iron-oxidizing bacteria, M. ferrooxydans relies on a form of soluble iron, called ferrous iron, or FeII, as a source of the electrons it needs to breathe. When plenty of oxygen is present, ferrous iron readily gives up its extra electron to the oxygen, to become the more stable FeIII, or ferric iron--the kind of iron oxide we know of as rust. But in lower-oxygen environments, M. ferrooxydans' can do oxygen's job for it, thereby gaining energy from the extra electron.
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