Fighting Farmland Pollution with Fungi

Fighting Farmland Pollution with Fungi

With support from the MnDRIVE Environment Initiative, doctoral candidate Laura Bender harnesses the power of soil fungi to help plants absorb pollutants.

by Kyle Wong

To ensure a healthy crop, Minnesota farmers carefully track soil health, nutrients and the quantity of water flowing through their fields. Since 2015, Minnesota’s Buffer Law also requires farmers to tend to historically overlooked land along the edge of these fields. The law mandates a 50-foot buffer along farm fields bordering public waterways, including irrigation and drainage ditches, to help reduce contamination from farm runoff. Instead of corn, soybean and other cash crops, buffer zones are full of perennial plants and trees adept at absorbing excess nutrients flowing from the fields. With financial assistance through environmental programs like the federal Conservation Reserve Program, farmers have both the mandate and the incentives to establish quality buffers. 

Like their commercial counterparts, plants in buffer zones naturally take up nutrients, but researchers like graduate student Laura Bender, hope to improve the process by focusing on fungi living beneath the soil. Soil fungi colonize the roots of buffer plants to form a symbiotic, or mutually beneficial, relationship. “These relationships help plants take up pollutants that would otherwise escape to the waterways, but soils are often degraded through decades of tillage and fertilizer application and compaction,” Bender notes. “The fungi communities that are naturally present in soil are often degraded or absent.” Supported by a 2018 MnDrive Environment seed grant, Bender works to restore those fungal communities to strengthen buffer plants and keep Minnesota waters clean. 

Bender works with several companies working with fungal amendments and measuring techniques. MycoBloom, for example, developed a fungal amendment containing a type of fungus called  arbuscular mycorrhizal (AM). AM fungi have been shown to help plants absorb nutrients more efficiently. But soil types vary across Minnesota, so Bender has worked with farmer Dave Legvold to test the amendment on the buffer zones on his farm. She collects data from his testing site each year to identify how well the amendment might work in the rest of Minnesota.

Bender collects soil and plant samples from the field site’s buffer zone and measures the level of phosphorus, one of the most common farm nutrients harmful to waterways. Alongside the buffer, she also collects dissolved groundwater. The Research Analytics Lab at the University of Minnesota processes the soil, plant and groundwater samples to calculate the phosphorus levels in each component. Bender uses the data to trace the amount of phosphorus that the buffer plants absorb and the amount that escapes to the water. “We’re measuring how the phosphorus level changes each year to see if the fungi amendment is removing it from runoff water that enters the buffer,” she says.

Phosphorus levels in the buffer are only part of the story; Bender wants to observe the interactions between the AM fungi and the buffer plants. To do so, she needs to look below the soil and analyze the mycorrhizal interactions at a microscopic level. Here, she partners with the company MycoRoots to assess how well the AM fungi colonize the roots of buffer plants. MycoRoots documents the surface area of plant roots covered by AM fungi. Bender uses the data to understand the role that mycorrhizal association plays in phosphorus uptake. Data from 2018 and 2019 revealed that plants with high root coverage from AM fungi tended to take up more phosphorus, leading to lower phosphorus levels in both the soil and groundwater. Bender will conduct more data analysis this fall before forming a conclusion. 

Ultimately, Bender hopes to guide state policy to help farmers understand the best practices for their buffers. To build awareness, Bender plans to lead an online workshop this fall to bring farmers, policymakers and industry partners together for a discussion on buffer-related issues and policies. “It’ll be related to specific topics – different fungi people have used, success or failures in certain settings, opportunities for collaboration, etc. The goal is to identify where others have used amendments and how it has worked for them.” 

With additional funding from MnDRIVE Environment and the University’s Institute on the Environment, Bender hopes to continue research and strengthen her partnerships with the community. Proper guidelines on buffer strips and fungal amendments can help Minnesota landowners establish healthy buffers that benefit them financially and help conserve the environment.

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

Kyle Wong is a writing intern in the University of Minnesota Science Communications Lab, majoring in Microbiology. He can be reached at wong0511@umn.edu

Signal and Noise        

Signal and Noise        

Enzyme-based coatings developed at the University of Minnesota help protect port infrastructure by disrupting the signals underwater bacteria use to communicate.

By Nick Minor and Kristal Leebrick

In any seaport or freshwater marina around the world, just beneath the surface, and you’ll find an ongoing battle between the boats, docks, bridges—anything made of steel—and a cast of aquatic bacteria in search of a submerged surface to call home. The biocorrosion created by these bacterial hitchhikers is especially dire in cold climates where winter brings the added wear and tear of scraping ice. And Duluth-Superior Harbor is ground zero, as aquatic bacteria corrode nearly 50,000 pounds of steel there each year.

Two University of Minnesota scientists—Randall Hicks, a microbial ecologist in Duluth, and Mikael Elias, a biochemist in the Twin Cities—have developed an enzyme coating they believe could rewrite the story of biocorrosion in Duluth and around the world. Their work shows extraordinary promise in helping prevent biocorrosion in seaports and could have the added bonus of being environmentally friendly.

The scientists’ collaboration began in late 2016, after Elias read about Hicks’s and postdoctoral associate Simon Huang’s work on testing anti-biocorrosion coatings in Gateway, published by the University of Minnesota BioTechnology Institute. The timing was auspicious for Elias. He and his students had recently engineered an enzyme that breaks down the chemical signals bacteria use to coordinate and build things like biofilm, a matrix of proteins and carbohydrates that can lead to biocorrosion. The interruption of those signals is like overlaying an impenetrable static onto construction workers’ walkie-talkies. Without the ability to communicate, the bacteria can’t coordinate enough to build anything.

Communication-disrupting enzymes are well-known and widely available, yet their potential ability to prevent bio-induced corrosion was unknown. In addition, in order to prevent biocorrosion in the Duluth-Superior Harbor, an enzyme needs to be hardy enough to withstand organic solvents of paints, temperature shifts that can kill most plants and animals, and endure scrapes from massive winter ice flows. This is where Elias’ specialty—protein engineering—came into play. Elias refined the enzyme to such an extent that it is now “so stable that we can dilute them into paint, a very harsh treatment for a protein,” says Elias, “and they still remain active.”

After reading about Hicks’s and Huang’s work, Elias reached out and asked if Hicks could squeeze one more coating into his tests. From there, the duo started with a two-month, proof-of-concept test in the lab, made possible through funding from the University’s MnDRIVE Environment initiative, which supports promising research on environmental remediation. In this short-term test, the enzyme, which was suspended in a durable acrylic, outperformed every other coating Hicks had been examining. But the real test lay ahead. After presenting the enzyme coating to companies like PPG, BASF, and Ecolab, Elias and Hicks heard the same message over and over: The companies needed to know if it would remain effective for years, not just two months.

Elias and Hicks received a much larger “demonstration grant” from MnDRIVE, which supported two years of testing, including testing in the Duluth-Superior Harbor. The work exceeded all expectations: over those two years, the enzyme coating was more effective at preventing biocorrosion than any other available coatings and it appears to do no harm to the environment as it kills nothing outright. Currently, 85 percent of the market for anti-biocorrosion coatings is dominated by toxic copper oxide paints. As with nearly every other coating available, copper oxide paints work by brute force, killing the organisms responsible for biocorrosion. Copper oxide’s toxicity to biocorrosive organisms also means it’s toxic to other living things.

Copper oxide paints were technically banned by multiple U.S. states. “But, because there is no alternative,” explains Elias, “the ban is constantly being pushed back.” Copper oxide, a heavy metal and potent environmental toxin, has been accumulating in portside ecosystems around the world for decades.

“The alternative that we’re working on,” says Elias, “is ecological because it’s a protein. A protein, by definition, is biodegradable. It’s amino acids.” The enzyme’s approach—disrupting the communication between bacteria that get biocorrosion started—is utterly novel.

The enzyme coating could rewrite the story of biocorrosion in Duluth and enable additional infrastructure protections to take effect. The aquatic ecosystem around the Duluth-Superior Harbor, along with similar portside ecosystems around the world, could start to recover from decades of copper pollution.

Based on their initial work, the team received funding from the Minnesota Sea Grant and Minnesota Aquatic Invasive Species Research Center-LCCMR to study the coatings’ ability to inhibit biofouling and the adhesion of aquatic invasive species to underwater surfaces.

“This may just be another arrow in the quill of possible coatings that could be used,” Hicks explains cautiously, “but potential applications are certainly way beyond Lake Superior. The market could be potentially unlimited.”

 

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Also see Battling Biocorrosion in Duluth-Superior Harbor