New UC Davis Study Reveals Why Ralstonia Bacteria Kill Plants So Fast
A slippery biofilm gives Ralstonia bacteria deadly speed in wilting crops like tomatoes and potatoes, UC Davis researchers find.
On January 28, 2026, researchers at UC Davis published groundbreaking findings on Ralstonia solanacearum, a plant-wilting bacterium that devastates crops like tomatoes and potatoes. Their study reveals that a slippery biofilm, made of a sugar-like molecule called EPS-1, allows the pathogen to spread rapidly through plant vessels, leading to swift crop death. This discovery deepens our understanding of crop disease mechanisms and could guide future control strategies.
Una nueva colaboración entre fitopatólogos e ingenieros de la Universidad de California, Davis, ha revelado por qué Ralstonia solanacearum es un potente destructor de cultivos. Este patógeno del suelo, conocido por causar marchitez bacteriana en tomates, patatas y otras hortalizas, utiliza una secreción viscosa y elástica para invadir y destruir sus plantas hospedantes.
Ph.D. Student Matthew Cope-Arguello collects goopy pink Ralstonia bacteria off of petri plates in the Lowe-Power Lab at UC Davis
Ralstonia can lie dormant in wet soil for years before activating. Once it infects a plant, it clogs the xylem-vessels responsible for transporting water-causing plants to wilt and die within days. "They cause a heart attack for plants," said Tiffany Lowe-Power, associate professor of plant pathology at UC Davis.
What sets this bacterium apart is its ability to produce a biofilm called exopolysaccharide 1 (EPS-1). While bacterial films often help with moisture retention, Ralstonia's version is uniquely "sloppy", said Lowe-Power. "Ralstonia are charismatically disgusting," she added, highlighting their sticky, slimy nature.
Understanding the fluid mechanics of this goop became possible thanks to a cross-disciplinary collaboration with Hari Manikantan, a chemical engineering professor at UC Davis, who specializes in complex fluids like saliva and lung surfactants. Using precision lab instruments, his team analyzed how the EPS-1 flows under stress-similar to conditions in plant xylem.
The findings were clear: Ralstonia's EPS-1 biofilm flows quickly under plant-like shear forces, allowing the bacteria to travel swiftly inside the plant, leading to widespread infection. "The question is what's the relevant time scale?" said Manikantan. "You bounce it, it's a solid. Leave it, and it oozes."
To determine if this biofilm property was unique, graduate student Matthew Cope-Arguello created a simple tilt test for bacterial colonies. His research confirmed that the drippy characteristic of EPS-1 is exclusive to pathogenic strains, setting them apart from harmless bacterial relatives.
This trait, now better understood, may become a target for future crop protection efforts, as scientists explore ways to block or neutralize EPS-1 production. The study also opens new doors for soft matter physics, as researchers can model bacterial flow dynamics with real biological consequences.
The research team included scientists from Ohio State, University of South Alabama, University of Massachusetts, University of Dayton, University of Wisconsin, University of Michigan, and University of Vermont, and was supported by the USDA, NSF, and the UC Davis Academic Senate.
As crop diseases driven by climate variability and global trade continue to threaten food security, insights into pathogen mobility and biofilm behavior offer timely and potentially transformative solutions.
