New discovery of how floating bacteria could help prevent disease spread and improve medical treatments

Bacterial swimming illustration

A research team led by the University of Minnesota Twin Cities studied how bacteria swim in complex fluids, providing insight into how the microorganisms move through different environments, such as in their natural habitats or in the human body. Photo credit: Cheng Research Group, University of Minnesota

University of Minnesota researchers studied for the first time how bacteria move through liquids containing small solid particles.

For years science fiction writers have written about the idea of ​​using microswimmers that could perform surgeries or administer drugs to people. Now a team led by researchers from the University of Minnesota Twin Cities has discovered how bacteria swim through various complex fluids and environments like the human body.

Their findings could help scientists develop new treatments for bacteria-causing diseases and design bacteria-based systems to deliver drugs into the human body.

The study was published in Nature, the world’s leading peer-reviewed, multidisciplinary scientific journal.

The University of Minnesota has a long history of swimming in liquids other than water. In 2004, Ed Cussler, then a professor in the Department of Chemical Engineering and Materials Science, compared the speed of a competitive college athlete swimming in water to a thick, syrupy guar gum solution. It led to an unexpected discovery (and an IgNobel prize) that people can swim just as fast in guar gum solutions as they can in water.

Nearly two decades later, a multidisciplinary team at the University of Minnesota has looked at the problem again, except the swimmers are now microscopic bacteria instead of varsity athletes. They discovered that bacteria swim even faster in viscous solutions than in water.

“Bacterial swimming,” as it’s commonly called in the research community, has been studied extensively by scientists since the 1960s. Previous studies have shown that bacteria swim faster in thick polymer solutions, namely liquids that contain polymers, which are substances made up of long-chain molecules. Researchers have theorized that this is because the bacteria can swim through the network formed by the chain molecules, stretching the chains to help propel them forward.

In this new study, however, the U of M team examined for the first time how bacteria move through solutions of small solid particles instead of chain molecules. Despite large differences in polymer and particle dynamics, they found that the bacteria still swam faster, suggesting there must be another explanation for how bacteria move through thick, complex fluids.

The U of M researchers have a possible answer. They believe that as the bacteria swim, the drag created by the passing of particles allows their flagella — or the “tail” bacteria that have that spin to propel them forward — to align better with their bodies , which ultimately helps them move faster.

A bacterial cell “wobbles” to move next to a micron-sized colloid particle. Video Credit: Cheng Research Group, University of Minnesota

“Ever since microscopes were invented in the 17th century, people have been fascinated by how bacteria swim, but until now understanding has mostly been limited to simple liquids like water,” explains lead author Shashank Kamdar, a University of Minnesota graduate student in chemical engineering and PPG Research Grant recipients. “But it’s still an open question how bacteria move in real situations, such as through soil and liquids in their own habitats.”

Understanding how bacteria move through complex, viscous environments — the human body is one of them — can help scientists develop treatments for diseases and even use bacteria as vessels for delivering drugs to humans.

“There are multiple mechanisms that people have used to explain this phenomenon over the decades, but with this study we provide a unified understanding of what happens when bacteria swim through complex solutions,” said Xiang Cheng, senior author of the Papers and Associate Professor in the Department of Chemical Engineering and Materials Science at the University of Minnesota. “And it is important to understand how bacteria move in a complex environment. For example, a certain type of bacteria causes stomach ulcers. The gastric mucosa is a viscous environment, so studying how the bacteria move in this environment is important to understand how the disease spreads.”

“In the end, we should all learn from bacteria,” Cheng added. “They keep moving despite resistance.”

Reference: “The Colloidal Nature of Complex Fluids Improves Bacterial Motility” by Shashank Kamdar, Seunghwan Shin, Premkumar Leishangthem, Lorraine F. Francis, Xinliang Xu, and Xiang Cheng, March 30, 2022, nature.
DOI: 10.1038/s41586-022-04509-3

In addition to Cheng and Kamdar, the team included Lorraine Francis, University of Minnesota College of Science and Engineering Distinguished Professor and 3M Chair in Experiential Learning, and Seunghwan Shin, graduate researcher from the Department of Chemical Engineering and Materials Science; and Beijing Computational Science Research Center researchers Premkumar Leishangthem and Xinliang Xu.

The research was supported by the National Science Foundation (NSF) and the University of Minnesota Industrial Partnership for Research in Interfacial and Materials Engineering (IPRIME). New discovery of how floating bacteria could help prevent disease spread and improve medical treatments

Russell Falcon

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