Rust-Breathing Bacteria: Miracle Microbes?

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He knew that microorganisms could live in oxygen-deprived environments by processing things such as sulfate and methane. If they could do that, Lovely reasoned, they might also be able to make a living from iron. Which is why, in 1987, Lovely scooped up the iron-rich mud from the Potomac River just downstream from Washington, D.C. Unbeknownst to him, the microbes therein would change his life.

Back in his lab, Lovley put the mud in a test tube, added some acetate—essentially vinegar, a favorite microbe food—and watched. Eventually, he noticed little black minerals collecting on the bottom of the tube amidst a sea of fluffy orange iron oxide, or rust.

"I put a magnet up to the side of the tube, and all the little pieces flew over to the side of the glass," Lovely said. "That was a 'Eureka!' moment."

The mud-dwelling microbes, which Lovley later named Geobacter metallreducens, obtained their energy by transferring electrons onto the rust. In the process, they turned the rust into magnetite.

Magnetite is the source of most of the magnetic material deposited on Earth some two billion years ago. Lovley and his colleagues concluded in a 1987 paper published in Nature that the microbes may have been responsible for most of these early magnetite deposits.

Microbes in Action

Since Geobacter metallreducens was discovered, Lovley and his colleagues have tried to figure out how to take advantage of this unique microbial metabolism, from cleaning up contaminated groundwater to generating electricity.

Magnuson, the Idaho State University microbiologist, believes that the ability of microorganisms like Geobacter to clean up groundwater may be of particular use to humans in the coming decades, as world populations are predicted to experience a water crisis.

He envisions using microbes not only to decontaminate water supplies but to protect them until human consumption.

"Using Geobacter to protect and maintain the quality of these aquifers might be a viable solution, seeing as we are going to run into water-quality issues," he said.

Lovley and his colleagues are not yet developing Magnuson's proposed superefficient water filters, but they are actively developing a method to remove uranium from billions of gallons of contaminated groundwater. (Related story: "Microorganism Cleans Up Toxic Groundwater".)

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