An End in Sight For “Forever Chemicals”

An End in Sight For “Forever Chemicals”

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

By Caroline Frischmon

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 research 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.

 

Understanding a Toxic Necessity

Understanding a Toxic Necessity

Jannell Bazurto, assistant professor of Plant and Microbial Biology at the University of Minnesota, is pursuing a better understanding of formaldehyde, a chemical that is carcinogenic, toxic, and produced by all living things.

By Reed Grumann

If you dissected a pig in high school biology, you might remember a sharp, acrid smell permeating the classroom and the teacher’s warning about a carcinogenic chemical called formaldehyde. Though often labeled a killer chemical, every organism on Earth, including humans, produces small amounts of formaldehyde. In very small quantities, it’s manageable. Produce or consume too much, and formaldehyde will kill otherwise healthy cells by attacking critical proteins and DNA.

While most organisms can neutralize small amounts of formaldehyde, researchers are just beginning to understand the mechanisms involved in formaldehyde regulation. Jannell Bazurto, a member of the BioTechnology Institute and an assistant professor of Plant and Microbial Biology, looks for clues in Methylobacterium, a type of bacteria that produces and neutralizes formaldehyde levels that would kill most other microbes.

As their name implies, methylobacteria have a unique ability to metabolize or breakdown, single-carbon molecules like methane and methanol. The process helps the cell maintain enough energy to survive, but also generates formaldehyde as an intermediate step. Fortunately, the bacteria are also uniquely equipped to handle sudden changes in concentrations of the toxin.

A key mechanism of Methylobacterium is an enzyme that converts formaldehyde into less harmful chemicals. While the enzyme is sufficient at normal levels of formaldehyde concentration, it’s not enough to handle exceptionally higher formaldehyde levels. To identify the function of two additional proteins suspected of playing a role in regulating formaldehyde levels, a group of researchers at the University of Idaho removed them from bacterial cells. And just like a cake without sugar and eggs, something was off. “If you don’t have [the two proteins] … you can see [the cells] accidentally overproduce formaldehyde, and they end up secreting it in the growth medium,” says Bazurto.

It’s still unclear exactly how these two proteins keep formaldehyde levels low in methylobacterium, but they aren’t alone in their efforts. Dozens of genes express proteins as formaldehyde levels change—a strong indicator of their importance in regulating the toxin. The challenge for Bazurto is knowing which of these genes, and the proteins they encode, actually play a role in formaldehyde metabolism. By manipulating each gene and looking at the results, Bazurto hopes to crack the code and establish which genes impact formaldehyde metabolism and their role in the process.

Once understood, these metabolic pathways could be hardwired into other microbes (like E. coli) through genetic engineering. Modified E. coli could consume methanol, neutralize formaldehyde, or produce marketable chemicals like biofuels and organic acids. In some facilities, formaldehyde is produced in large quantities as a building block for other chemicals. Wastewater remediation at these facilities would greatly benefit from bacteria genetically modified to directly consume formaldehyde and withstand toxic concentrations.

Throughout its industrial lifecycle, formaldehyde has the potential to creep into our air and water, putting humans at risk of exposure. The relationship between excessive formaldehyde exposure and human health issues—cancer, respiratory issues, and skin irritation—has been well established, yet we still know very little about how humans (and other organisms) sense and handle exposure to formaldehyde. As the search for practical applications in biotechnology, medicine, and environmental remediation continues, Bazurto remains fascinated by the basic science and “scenario where we actually know how to resolve formaldehyde toxicity itself.”

Reed Grumann is a writing intern in the Science Communication Lab, majoring in microbiology and political science. He can be reached at gruma017@umn.edu.

Image courtesy of Janelle Buzurto. Timecourse of Methylobacterium chemotaxing toward a capillary tube that has a formaldehyde plug in it. (Zero and five minutes). Cells seen faintly in the background at zero minutes begin to move toward the plug by the five minute point, forming a halo around the end of the tube.

 

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