## bacteria Find a New Way to move: ‘Swashing’ Without Flagella
New studies from Arizona State University reveal surprising ways bacteria can move without their flagella – the slender, whip-like propellers that usually drive them forward.
Movement lets bacteria form communities, spread to new places or escape from danger.Understanding how they do it can definitely help us develop new tools to fight against infections.
In the frist study, Navish Wadhwa and colleagues show that salmonella and E. coli can move across moist surfaces even when their flagella are disabled. As part of their metabolism, the bacteria ferment sugars and set up tiny outward currents on the moist surface. These currents carry the colony forward, like leaves drifting on a thin stream of water.
The researchers call this new form of movement “swashing.” It may help explain how harmful microbes successfully colonize medical devices, wounds or food-processing surfaces. Understanding how metabolism drives bacterial movement could help researchers develop new techniques to limit infections, for example by changing local pH or sugar availability.
“We were amazed by the ability of these bacteria to migrate across surfaces without functional flagella. Actually, our collaborators originally designed this experiment as a ‘negative control,’ meaning that we expected (onc rendered) flagella-less, the cells to not move,” Wadhwa says. “but the bacteria migrated with abandon, as if nothing were amiss, setting us off on a multiyear quest to understand how they were doing it.
“It just goes to show that even when we think we’ve got something figured out, there are ofen surprises waiting just under the surface, or in this case, above it.”
Navish Wadhwa, arizona State University
Wadhwa is a researcher with the Biodesign Center for Mechanisms of evolution and assistant professor with the department of Physics at ASU.
The study appears in the Journal of Bacteriology. The paper has been selected by the journal as an Editor’s Pick, highlighting the importance of the research.
Sugar-fueled swashing
When bacteria feed on sugars like glucose, maltose or xylose, they sometimes give off acidic by-products such as acetate and formate. These by-products draw water from the surface, creating currents that push the bacteria outward. Fermentable sugars are essential for this process – without them, the microbes can’t move in this way. sugar-rich environments in the body, such as mucus, may actually help harmful bacteria spread and cause infection.
When researchers added detergent-like molecules known as surfactants to the colonies, the bacteria stopped swashing. In contrast, surfactants did not affect swarming, a coordinated, flagella-powered form of movement that lets bacteria spread rapidly across moist surfaces. This suggests the two forms of movement use distinct physical mechanisms, and that surfactants that can be used to selectively suppress (or enhance) the movement of bacteria depending on whether they are swashing or swarming.
The fact that bacteria can colonize surfaces even when their normal swimming machinery is impaired has important implications for human health. Some microbes may spread by swashing across medical catheters, implants and hospital equipment. Blocking flagella alone may not be enough to stop them. Instead, we may need to interfere with the chemical processes they use to power this movement.
Both E. coli and salmonella can cause foodborne illness. Knowing they can spread on surfaces through passive fluid flows may help improve how food processing plants design cleaning protocols. And because swashing depends on fermentation and acidic by-products, strategies that alter surface pH or sugar availability could reduce bacterial colonization. The study showed that simple changes in acidity were en
Summary of the Research on Flavobacteria and the T9SS
This research focuses on flavobacteria, a type of bacteria that moves differently than E. coli. Instead of swimming,they glide across surfaces using a complex molecular machine called the Type 9 Secretion System (T9SS). Here’s a breakdown of the key findings:
* T9SS as a “Molecular conveyor Belt”: The T9SS works like a microscopic snowmobile, using an adhesive-coated belt to pull the bacterium forward.
* GldJ as a “Gear-Shifter”: Researchers discovered that a protein called GldJ within the T9SS controls the direction of the motor. Deleting a small part of GldJ reverses the motor’s spin, changing the bacteria’s movement.
* Dual Role in Health: The T9SS has both harmful and beneficial implications for human health:
* Harmful: In the oral microbiome, it contributes to gum disease and potentially linked to heart disease and Alzheimer’s by promoting inflammation.
* Beneficial: In the gut microbiome, it can strengthen immunity and improve the effectiveness of oral vaccines by protecting antibodies.
* Potential Applications: Understanding the T9SS “gearbox” could lead to:
* Blocking Biofilm Formation: Preventing infections and contamination of medical devices.
* Targeted Microbiome therapies: Harnessing the beneficial properties of the T9SS to promote health.
* Broader Implications: The research highlights the need to move beyond conventional approaches (like targeting flagella) in combating bacterial disease and consider controlling the bacterial surroundings (sugar levels, pH, surface chemistry) and disrupting key molecular machines like the T9SS.
* Further Research: The team aims to determine the high-resolution structure of the T9SS to understand how its parts interact and respond to feedback, potentially inspiring new bioengineered nanomachines.
In essence, this research reveals a complex mechanism for bacterial movement and secretion, with significant implications for both understanding bacterial evolution and developing new strategies to combat and harness the power of the microbiome.