Fighting Farmland Pollution with Fungi

MnDRIVE researchers Mikael Elias and Lawrence Wackett are studying Acidimicrobium in hopes of harnessing the bacteria’s PFAS-degrading power.

Waterproof, nonstick and flame retardant. Products like raincoats, frying pans and firefighting foam keep us safe, clean and comfortable. Their durability stems from the presence of carbon-fluorine bonds, which are some of the strongest in organic chemistry. Unexpectedly, these great modern conveniences have also created a widespread environmental problem. Compounds with multiple carbon-fluorine bonds, called PFAS (perfluoroalkyl substances), have accumulated for decades in the environment with no effective way to break down these “forever chemicals.” 

Exposure to PFAS through drinking water is associated with higher cholesterol, certain cancers and suppressed immune responses. Scientists and regulators have tried to address the PFAS contamination through filtering, coagulating, burning and more, but most cost-effective solutions simply concentrate the chemicals and move them away from wells, aquifers and other points of human contact. Now, there’s hope that a bacteria called Acidimicrobium sp. might hold the key to a more permanent solution. Through a MnDRIVE Environment Seed Grant, researchers Mikael Elias and Lawrence Wackett, both University of Minnesota professors in the Department of Biochemistry, Molecular Biology, and Biophysics, will study the bacteria’s promising ability to digest PFAS.

Last year, researchers at Princeton University discovered Acidimicrobium could digest PFAS chemicals and convert them to carbon dioxide and fluoride. It’s the first identified bacteria that actually breaks the carbon-fluorine bond, but scientists are wary of calling it a solution quite yet. The microbes eat too slowly on their own to be effective at the scale needed to address PFAS contamination in the environment. To speed up the process, Elias and Wackett will first need to identify the enzymes that give Acidimicrobium its superpower.

All living things use enzymes, or biological catalysts, to accelerate chemical reactions. They are highly specific to one job, whether it’s digesting fats or sugars or assisting in DNA production. Out of all Acidimicrobium’s enzymes, scientists aren’t sure which ones are responsible for the PFAS reaction. “What we’re really going after now is to identify and characterize the actual enzymes responsible for the degradation process,” states Elias. That understanding will pave the way for improving their efficiency through genetic modification. Eventually, the team hopes to develop the enzymes as a PFAS bioremediation tool.

Wackett and Elias partnered on this project to share their varying expertise. Wackett, an enzymologist, will analyze the bacteria’s DNA sequence to identify which enzymes are likely responsible for PFAS degradation. Elias, a structural biologist, will determine how the structure of Wackett’s enzymes facilitates the reaction. 

Using 3D images to reveal the structure of the enzyme’s active site, Elias examines the arrangement of amino acids, the building blocks of enzymes. “We’re going to look at how the amino acids in the enzyme break down the PFAS molecules,” explains Elias. With that information in hand, he and Wackett will try to engineer better enzymes by manipulating the arrangement of the amino acids.

 In addition to engineering a more efficient Acidimicrobium enzyme, Wackett and Elias will search for other potential PFAS-degraders with related DNA sequences. Bacteria with similar enzymes as Acidimicrobium might digest PFAS even more efficiently, but scientists haven’t been able to test for them yet. “When we have the sequence code, we will know how to look for the enzymes and the genes in other bacteria,” says Wackett, “That’s another big advantage of having the structure and knowing those key amino acids.”

Existing PFAS technologies focus on sequestration rather than degradation. “[Containment] is useful until you have a better solution, but it’s imperfect because it has limited capacity,” Elias points out. “You’re just moving pollutants from one place to another.” The MnDRIVE seed grant provides an opportunity for a better solution. Elias and Wackett hope Acidimicrobium will help them finally eliminate these forever chemicals for good.

This work was supported by MnDRIVE Advancing Industry, Conserving Our Environment at the University of Minnesota.

Caroline Frischmon is a Science Communication Fellow in the Science Communications Lab and is majoring in Bioproducts and Biosystems Engineering. She can be reached at frisc109@umn.edu.