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A PNNL research paper on biofilms is featured on the cover of the Journal of Biophotonics. Enlarge Image

Biofilms. They're everywhere. Stuck to our teeth. Attached to boats. Plastered on pond stones. The thin, slimy film of microorganisms adhere to surfaces that are regularly in contact with water, and they can cause a host of problems.

Understanding the characteristics of biofilms is necessary for solving the problems they present. But biofilms are difficult to characterize when fully hydrated because their soft structure and water-like bulk properties make them extremely susceptible to damage. A group of PNNL researchers recently found a solution to this issue, making it possible to characterize biofilms without destroying them by utilizing white light interferometry.

In healthcare, biofilms cause over 80 percent of all infections, and are highly resistant to antibiotics and antimicrobial agents. In industry, biofilms accelerate rates of corrosion, increase drag on ship hulls, reduce the efficiency of heat exchangers, and decrease flow in plumbing.

But biofilms aren't entirely bad. They can be used to treat sewage and industrial waste, increase plant and animal health, and support global nutrient cycling.

Characterizing Biofilms

Although they each specialize in different areas of expertise, the group of PNNL researchers joined forces because they wanted to study a common issue.

“We want to understand the growth and structure of biofilms to understand how they colonize and spread on a surface, how they react to changes in their environment, where different metabolic activities occur, and how different materials or treatments might be used to control or eliminate them,” said Coastal Sciences researcher George Bonheyo.

Throughout their study, the researchers focused on the P. putida biofilm. By developing a technique for studying biofilm features and growth rates that utilizes white light interferometry, the researchers were able to study the biofilm without harming it.

They monitored growth from initial colonization to the point where it had fully matured. Using an adapted white light interferometry technique—which relies on light waves to measure surface height—researchers measured and monitored the thickness and arrangement of live biofilms, creating a 3D topographical map.

Findings

The thickness measurements of the biofilms followed expected trends for bacterial growth. Increased biofilm thickness often creates anaerobic conditions at the base of the film, leading to increased bio-acid production and corrosion.

Surface roughness also increased over time. A leading indicator of biofilm growth, surface roughness has a direct impact on hydrodynamic drag, which impacts how fast a vessel can move through water or how easily water can be passed through a pipe. A research paper on the study, which was funded by PNNL’s Chemical Imaging Initiative and the Intelligence Community Postdoctoral Research Fellowship Program, was highlighted on the cover of the June issue of the Journal of Biophotonics.

So what are the next steps now that researchers are able to characterize these aspects of biofilms?

“We are proposing to use the technique to understand how micro-textured surfaces affect where and how biofilms form,” said Bonheyo. “We are also proposing to use this technique to help quantify the impact microbial biofilms have on global carbon and nutrient cycling.”

PNNL Research Staff: George Bonheyo, Curtis Larimer, Jonathan Suter, and R. Shane Addleman