Current News
26 July 2011University of Houston / PNAS
How bacteria move
Scientists have studied how bacteria move along various surfaces before they form potentially dangerous biofilms. The study could help researchers develop anti-bacterial surfaces, they report in the Proceedings of the National Academy of Sciences.
Jacinta Conrad, an assistant professor of chemical and biomolecular engineering at the University of Houston, and her colleagues used a digital camera affixed to a microscope to videotape hours of moving bacteria. They then analyze these tens of thousands of images to determine exactly how they cross surfaces before forming biofilms, colonies of potentially dangerous bacteria that can be found in industrial, natural and hospital environments.
Biofilms can form on food processing equipment, potentially leading to food-borne illnesses, and on medical implants, leading to high rates of infection in hospitals. They also can disrupt the flow of sewage and oil pipelines and increase drag on marine vessels, slowing ships and wasting fuel, among other things.
In a previous study, Conrad and her collaborators detailed how bacteria use hair-like appendages called pili to pull themselves upright and "walk" across a surface. The work was published last fall in „Science“. The research in the PNAS paper builds on that finding, with researchers discovering that the bacteria employ a "slingshot" motion to move using multiple pili, which act as grappling hooks. Conrad said that bacteria rapidly "snap" to a new orientation when they release one pilus, while others remain attached. This is because the bacteria re-orients in the direction of the net force from the remaining attached pili.
"We think the bacteria use this rapid-snap motion to move forward," she said. "We believe that this method allows the bacteria to move faster and more efficiently across a surface through this sticky, viscous pre-matrix substance that surrounds it. The bacteria may use less energy this way." As they move across a surface, bacteria excrete certain polymers. These polymers form the basis of an extracellular matrix surrounding and protecting bacteria within biofilms.
This substance can be very thick and difficult to move through. The researchers hypothesize that the "slingshot" motion thins the sticky goo and makes it easier for the bacteria to travel through it. The next step is for Conrad and her collaborators to thoroughly test this hypothesis.
F. Jin, J. C. Conrad, M. L. Gibiansky, and Gerard C. L. Wong: Bacteria use type-IV pili to slingshot on surfaces. PNAS 2011, published ahead of print July 18, 2011, doi:10.1073/pnas.1105073108
