Bacteria use their pili to move (Image: Dr. Terry Beveridge/Visuals Unlimited, Inc.)

Like tiny mountaineers, bacteria use grappling hooks to pull themselves across a surface – and can get an extra boost by releasing one of the taut lines to slingshot themselves forward. Thwarting them could help combat the biofilms behind hospital infections.

Fan Jin and Gerard Wong of the University of California, Los Angeles, filmed the bacterium Pseudomonas aeruginosa crawling through a viscous medium on a glass surface. They then analysed how it moved using an algorithm. This confirmed what biologists had long suspected: many bacteria use hair-like appendages called pili as grappling hooks to pull themselves along a surface.

But the algorithms also picked up on something else: sometimes a bacterium’s rear end performed a jittery but purposeful little dance. Instead of merely contracting their pili, the bacteria released one taut pilus from the surface altogether, sending their behinds skittering across the surface. This fired the cell forwards 20 times faster than contracting pili.


“The paper is interesting and suggests aspects of pilus-based cell movement that I had not considered,” says Mark McBride of the University of Wisconsin-Milwaukee, who also studies bacterial movement but was not involved in the study.

This slingshot movement is so fast that Jin and Wong think it reduces the local viscosity of the medium by a process called shear thinning. The lower the viscosity, the easier it is to move – a huge advantage if you are a bacterium rushing to join your brethren and form a biofilm.

“The goal now is to find a way to target how they move” and prevent biofilms forming, says Wong.

Journal reference: Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1105073108