I’ll never forget the time I neglected my hot tub a little too long, returning to find a foul smell and a gross, clogged filter. Fortunately for me, a good scrubbing and refilling the tub with fresh water, followed by a couple of shock treatments, convinced me that the tub was safe for human habitation again. Let the relaxing begin!

Research at Purdue University won’t help stop me from neglecting routine home maintenance projects, but it could someday lead to a hot tub more resistant to bacteria and biofilms. Even more important, it could identify ways to prevent and eliminate the slimy films inside industrial piping and cooling equipment, where they decrease heat transfer efficiency and drive maintenance and water treatment costs.

Although chemical water treatment methods are effective at controlling biofilms in industrial water systems, organisms can develop biocide-resistant strains. Rather than looking at ways to kill the bacterial colonies once they have gained a foothold, researchers at the West Lafayette, Ind.-based university focused on the mechanisms the individual bacteria cells use to propel themselves. Certain interactions cause the bacteria, which secrete a mucus-like “extracellular polymeric substance,” to swim close to surfaces, say the researchers.

“New findings reveal specifics about interactions that induce bacteria to swim close to surfaces, where they remain long enough to attach and form biofilms,” says the university’s Emil Venere. “Most bacteria are pushers, and the findings showed that pushers swim closer to surfaces in the presence of the extracellular polymeric substance…Such knowledge could lead to methods that hinder the ability of bacteria to stick to surfaces.”

“Most research done on hydrodynamic interaction of bacteria on surfaces neglects the role of these polymers,” said Arezoo Ardekani, an assistant professor in Purdue University’s School of Mechanical Engineering. “And what we show is that this extracellular polymeric substance can also change the hydrodynamic forces that lead to bringing these cells close to the surface.”

The research was published in a special issue of the journal Rheologica Acta on August 31, and the research paper is available online here.


Linda Becker, Associate Publisher and Editor,