Extreme microbe may change how apples are protected

A compound derived from a microorganism belonging to a unique branch of life known for surviving in extreme conditions could soon provide Washington fruit producers with a new weapon to combat two of the most economically damaging pathogens facing the fruit industry.

Washington State University researcher Cynthia Haseltine has spent nearly a decade developing and testing the compound in her laboratory, but the work is now moving into the field with support from a $141,293 Washington Tree Fruit Research Commission grant aimed at evaluating the compound's real-world potential against fire blight and Listeria.

"This work has the potential to make a real difference for Washington's tree fruit industry," Haseltine said. "If it performs as expected, it could help growers better manage fire blight in orchards while also reducing costly Listeria risks in packing facilities."

Haseltine, an associate professor in the WSU College of Veterinary Medicine's School of Molecular Biosciences, has dedicated her career to studying archaea, microorganisms known for their ability to thrive in extreme environments such as boiling acid, deep sea hydrothermal vents, and salt crystals. One of those microorganisms is key to her compound, which has shown promising effectiveness in laboratory settings against a variety of harmful pathogens, including those that cause fire blight and listeriosis.

Fire blight can wipe out entire orchards and is among the most serious threats facing Washington's tree fruit industry, which produces nearly two-thirdsof the nation's apples. Losses attributed to the disease exceed $100 million annually nationwide.

Current treatment and prevention strategies rely on antibiotics like streptomycin, which is losing its effectiveness due to resistance, and copper-based products that raise environmental concerns.

If it performs as expected, it could help growers better manage fire blight in orchards while also reducing costly Listeria risks in packing facilities.

While fire blight is an issue in orchards, Listeria can contaminate fruit at multiple points, including during harvesting, processing and packing. Although only 10 to 25 cases are reported annually in Washington, incidents can result in millions of dollars in losses and serious illness in consumers.

"Listeria is a major economic problem in packing lines," Haseltine said. "Recalls can cost between $5 million and $15 million, and beyond that, growers absorb the loss of fruit that can't be sold and the reputational damage that comes with it."

The grant will help to fund a two-yearproject that will focus on scaling production of the compound, evaluating its stability under different environmental conditions and conducting the first orchard and packing-line trials.

The compound has several traits that make it promising. Because it is derived from microorganisms adapted to extreme environments, it remains stable across a wide range of temperatures and conditions common in orchards and packing facilities. It has also shown effectiveness against pathogens within biofilms - protective layers bacteria form on surfaces to shield themselves from disinfectants and antibiotics. In addition, while the targeted pathogens are becoming increasingly resistant to antibiotics, that is unlikely with the compound.

"There's a really low chance for resistance developing," Haseltine said. "For that to happen, it would require multiple simultaneous mutations that are, statistically, very, very unlikely, whereas antibiotic resistance is often a single mutation."

Field testing is already underway through partnerships with WSU Extension. Orchard trials are being led in Wenatchee by tree fruit specialist Tianna DuPont, while Claire Murphy, a food safety expert in Prosser, is providing packing-line relevant listeria isolates and additional expertise for further research in Haseltine's lab.

"Moving this out of the lab and into real-world conditions is a critical step," Haseltine said. "We need hard data from trees and from listeria in packing-lines to understand how the compound performs and whether it can become a practical tool for growers."

Haseltine said the ultimate goal is to generate enough data to attract commercial partners capable of producing the compound at scale.

The Washington Tree Fruit Research Commission, established by the Washington state Legislature in 1969, funds industry-driven research aimed at improving the production, handling and marketing of Washington tree fruit. Its grants are funded directly by growers.

"This work has the potential to impact growers quickly," Haseltine said. "If it succeeds, it could benefit farmers, consumers and the broader food system in Washington and beyond."

Haseltine is working with the Innovation and Entrepreneurship team in the WSU Office of Research to explore the commercial potential of this innovation, and anyone interested in collaboration or licensing opportunities should reach out to [email protected].