Bacteria-Inspired Pumps Purify Water
|E. coli bacteria grown in a lab.|
The drugs people take and feed to livestock ultimately get washed into waterways, where harmful bacteria like E. coli grow and evolve to be resistant to those same antibiotics.
A new study has shown that the same mechanisms that allow E. coli bacteria to expel drug molecules can also be used to extract the drugs from polluted waters.
E. colihave evolved proteins called efflux pumps, said study author David Wendell, a research assistant professor at the University of Cincinnati. The proteins bind to "noxious compounds" and remove them from the cell. "It's a selective garbage disposal," he said.
Wendell added that at a science conference, he watched a fellow researcher describe how E. coli had evolved the efflux pumps, and how the pumps meant that E. coli posed a greater health hazard. "I thought, 'Wouldn't it be great to use these to capture stuff?' Instead of pumping stuff out, they'd be pumping stuff in," Wendell said.
Back in his lab, he attached the protein pump to another protein that provided an energy source when struck by green light. The resulting substance was a cloudy, yellow-red solution. "It's a little soupy," Wendell said.
Yet inside that soup were millions of tiny pumps, each barely wider than a human hair, pumping antibiotics out of polluted water into bubbles called vesicles. The bacterial pumps removed nearly twice the antibiotics from the water compared to activated carbon, the current standard for cleaning up pollution (and just like what's found in a Brita water filter). [Read also: Cheap, Sustainable Water Filter Made from Seeds and Sand]
In theory, Wendell said, "you could take out the vesicles and remove them. You could break them open, like an egg, and extract the antibiotics to reuse them." Activated carbon, on the other hand, is burned after use.
These bacterial pumps don't just remove antibiotics. The team also tested the pumps' ability to remove ethidium bromide, a carcinogen. Others pump out heavy metals or hormones.
And there's another intriguing possibility that has yet to be tested, Wendell said. "There are pumps specific to heavy metals," he said, "but also silver and copper." Those pumps could be used to help extract dissolved precious metals from water.
The study was published in the journal Nano Letters on April 13.