The world of unicellular microorganisms is vast and complex; a whole universe of activity that the naked eye can't see. It's a place rich with activity and potential, which makes it a wonderland for researchers.
One type of bacteria, those that oxidize iron, have been difficult to study because they are difficult to grow and research in the lab. Iron oxidizers "eat" electrons from dissolved iron, which results in large amounts of rust. These iron-oxidizing bacteria are found all over the globe in places where oxygen-rich aerobic environments meet oxygen-lacking anaerobic environments. They are a big part of the global cycling of iron, and they play a major role in the corrosion of steel pipelines, bridges, piers and ships.
Scientists have long been interested in the unique properties of iron-oxidizing bacteria, and now, new research has paved the way to cultivate these bacteria using electricity instead of iron. The work was published on Jan. 29 in mBio, the journal of the American Society for Microbiology.
The new method, called electrochemical cultivation, gives the bacteria a steady stream of electrons — instead of iron — that the bacteria can use to "breathe.”
"It's a new way to cultivate a microorganism that's been very difficult to study. But the fact that these organisms can synthesize everything they need using only electricity makes us very interested in their abilities," says Daniel Bond of the BioTechnology Institute at the University of Minnesota, Twin Cities, who co-authored the paper with Zarath Summers and Jeffrey Gralnick.
Bond and his team added a marine iron oxidizer along with nutrients to an electrode tuned to provide electrons at the same level as dissolving iron would provide. The idea was to "fool the bacteria into thinking they're at the world's best buffet,” Bond said.
And fooled they were. The bacteria multiplied and formed a film on the electrode, and eventually the researchers were able to grow the bacteria with no iron in the medium, proof that the bacteria were living off the electrons they absorbed from the electrode to capture carbon dioxide and replicate.
It’s the capture of carbon dioxide that is exciting. It could allow the process of electrochemical cultivation to be used to generate biofuels. It’s possible that electricity generated from renewable sources could be directed to iron-oxidizing bacteria, which would in turn combine it with carbon dioxide to create fuel. It would provide a way to take the ephemeral energy in electricity and turn it into a tangible, storable product.
"Bacteria are experts at the capture of carbon dioxide. They build cells and compounds" with the carbon, Bond says. Although the new process may be loaded with potential, getting from here to carbon-rich compounds we could use as fuel may be a long way off. Nonetheless, the work is a promising step.
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