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Cleansing the world’s water
Research at the University of Minnesota is taking aim at breaking down “forever” chemicals

Ever accidentally gulp lake water during an afternoon swim? You may want to spit that out, especially after you hear the list of pollutants that have been found in countless lakes in Minnesota and across the country.

Though the concentrations are often very low, certain drugs, heavy metals, “forever” chemicals—basically anything you flush down the toilet, dump in the trash or spray on your lawn—will find its way into local water sources. Small amounts may even be in drinking water.

Tom Niehaus, a professor in the College of Biological Sciences’ Department of Plant and Microbial Biology, is in the process of characterizing several species of bacteria in water that can degrade metformin, a popular drug used to treat type 2 diabetes.

“The first documentation of a bacteria that can metabolize metformin was from a bacteria found at the wastewater treatment plant in Saint Paul,” says Niehaus.

He initially worked with Larry Wackett—a Distinguished McKnight Professor in the Department of Biochemistry, Molecular Biology, and Biophysics—to fund Katie Wissbroecker, a graduate student who spearheaded the project. “Katie actually went there and collected the activated sludge that we were able to isolate these bacteria from.”

Collectively, Niehaus and Wackett have identified at least six metformin-degrading bacteria in their research. Wackett’s team was the first to identify the gene encoding the drug-degradation enzyme.

What Niehaus finds especially intriguing is that, after their discovery, people have started documenting metformin-degrading bacteria all over the world. The drug-degradation gene seems to have jumped from a bacteria’s genome to bacterial “plasmids,” circular pieces of DNA bacteria that can pass on to other bacteria (even bacteria of another species).

“The trait essentially went viral,” Niehaus says. “It’s impressive how quickly bacteria can adapt to these environments. It really shows how they act sort of like nature’s natural buffer.”

Because bacteria are relatively simple to study, are manipulable, and evolve relatively quickly (even in nature), they may play an important role in future water remediation projects.

Upping the ante

To Wackett, however, the only thing better than a natural buffer is a super-natural buffer. Some naturally occurring bacteria already possess traits that help them break down plastic, bind to metals, or survive in toxic environments.

But scientists like Wackett are experts at engineering (genetically “tweaking”) bacteria to become even more efficient at specific jobs like breaking down pollutants.

And that’s exactly what Wackett is interested in doing. His research interests revolve around engineering bacteria so they can effectively break down the most stubborn of toxins, including the “forever chemicals” polluting the Twin Cities’ east metro area.

Bacterial breakdown

Forever chemicals—also known as per- and polyfluoroalkyl substances (PFAS)—are so named because they don’t degrade in nature and are among the most challenging of toxins to remove from water. They’re so indestructible that before they were used for nonstick cooking pans, raincoats, and heart valve replacements, they were used to resist corrosion from reactive chemicals in World War II explosives.

By the time several forever chemicals were publicly linked to cancer and developmental health issues, they were already ubiquitous in our drinking water. Unless we remove them ourselves, they’ll persist in nature for up to 10,000 years.

“Bacteria haven’t evolved the processes to break down forever chemicals,” says Wackett. Most modern methods used to eliminate forever chemicals from the environment involve completely removing a contaminated source (i.e. valuable drinking water or layers upon layers of topsoil) and either storing it indefinitely or degrading it at an extremely high heat.

“But we do know of an enzyme that can break down smaller fluorinated molecules than the ones found in forever chemicals—if forever chemicals can be broken down they don’t present as much of a concern.”

Wackett’s team is engineering a Pseudomonas putida bacterium (in his words, “speeding up evolution”) so it can break down the longer fluorinated chains found in forever chemicals.

So far his research has had mixed success. The current rendition of the bioengineered bacteria can break down the long fluorinated chains, but the bacterium suffers stress from the fluoride released while doing so. They are now engineering bacteria to become more resistant to fluoride, making them effective PFAS degraders.

Support faculty research like Niehaus and Wackett’s in the College of Biological Sciences.

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