From soil to salad: How engineers are tracking the hidden journey of listeria
Article By Courtney Sakry Published June 4, 2026
Article Source: https://news.vt.edu/articles/2026/05/eng-cee-food-safety-listeria.html
Every time you rinse fresh lettuce for a salad, slice fruit for your kids, or grab packaged produce from the grocery store, there is an invisible world traveling alongside that food: bacteria. Most of it is harmless, and some of it is helpful. But certain bacteria, like listeriosis-causing listeria, can cause serious illness if they make their way from soil and water into the foods we eat.
Even more worrisome, research by Jingqiu Liao, assistant professor of civil and environmental engineering, has found that listeria bacteria adapts to survive in the harsh environments of food-processing facilities and fresh foods, making the bacteria more dangerous to human. Liao recently received the Larry Beuchat Young Researcher Award from the International Association for Food Protection for her work to improve food safety, trace outbreaks faster, and reduce contamination before it reaches people’s kitchens.
What is listeria and why does it matter?
While many types of listeria are harmless, one species — Listeria monocytogenes — can cause serious illness, especially in older adults, pregnant women, and people with weakened immune systems.
These bacteria are surprisingly common in the natural world. They can live in soil, water, and decaying plant material, but they are also found in food-processing facilities and on fresh foods like fruits and vegetables.
Unlike foods that are cooked before eating, fresh produce often does not go through a “kill step” that destroys harmful bacteria. If bacteria enter the food supply at any point, from the field to the processing plant, they can potentially make people sick.
"Tracking listeria in natural reservoirs and food production environments using these genomic tools helps identify where contamination originates and how it persists and spreads," said Xiangyu Deng, professor in the Center for Food Safety at the University of Georgia and one of Liao's research collaborators. "This helps to see where interventions can most effectively prevent human exposure."
How bacteria adapt to survive
Liao teamed up with researchers from Cornell University and University of Georgia to better understand how listeria survives in both natural environments and human-made food environments. Researchers analyzed the genomes — essentially the instruction manuals — of hundreds of listeria samples collected from soils in natural environments, agricultural water, and produce-processing facilities across the United States. This work builds on their previous studies of listeria in clinical settings.
What Liao and her collaborators found was that listeria strains living in nature and those living in food-related environments appear to adapt differently over time. “They may gain or lose genes that help protect their outer surface and use different available nutrients,” said Liao. “This allows them to cope with the stress they face in these environments.”
Some bacteria evolve to survive stressful conditions commonly found in food facilities, including cold temperatures, salty conditions, cleaning chemicals, and acidic environments. In other words, bacteria that survive in food-processing spaces are often specially equipped to handle the exact conditions designed to stop them. That’s why experts emphasize aggressive environmental monitoring, rapid response to positive swab tests, targeted cleaning of hard-to-reach sites where listeria can persist, and improved control of environmental conditions — especially moisture, which has been linked to the growth and survival of listeria.
The study also found that bacteria living in soil and natural ecosystems are adapted to very specific surroundings. Soil type, climate, land use, and even the presence of other bacteria can influence which listeria strains survive in a particular place.
Using genomics to trace outbreaks faster
Using machine learning, researchers were even able to predict where certain listeria strains came from based on their genetic makeup.
That could become a powerful tool during foodborne illness outbreaks. If scientists can quickly determine whether a strain likely came from soil, agricultural water, or a food-processing facility, investigators may be able to trace contamination faster and stop outbreaks sooner.
The research highlights something larger: the connection between the natural environment and human health. Bacteria do not stay confined to one place. What happens in soil, water, and agricultural systems can eventually affect grocery stores, kitchens, and dinner tables.
Liao’s goal is to help improve the safety of the foods we buy and eat. Understanding how harmful bacteria survive and spread can help food companies improve sanitation practices, help farmers reduce contamination risks, and help public health officials respond more effectively when outbreaks happen. “At the end of the day, this research is about keeping everyday food safer,” said Liao. “We want to help prevent contamination earlier and reduce the risk of foodborne illness for families and communities.”