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Edited by Bill Costerton, Allegheny-Singer Research Institute, Pittsburgh, PA, and accepted by the Editorial Board June 19, 2011 (received for review March 31, 2011)
Abstract
Bacteria optimize the use of their motility appendages to move efficiently on a wide range of surfaces prior to forming multicellular bacterial biofilms. The “twitching” motility mode employed by many bacterial species for surface exploration uses type-IV pili (TFP) as linear actuators to enable directional crawling. In addition to linear motion, however, motility requires turns and changes of direction. Moreover, the motility mechanism must be adaptable to the continually changing surface conditions encountered during biofilm formation. Here, we develop a novel two-point tracking algorithm to dissect twitching motility in this context. We show that TFP-mediated crawling in Pseudomonas aeruginosa consistently alternates between two distinct actions: a translation of constant velocity and a combined translation-rotation that is approximately 20× faster in instantaneous velocity. Orientational distributions of these actions suggest that the former is due to pulling by multiple TFP, whereas the latter is due to release by single TFP. The release action leads to a fast “slingshot” motion that can turn the cell body efficiently by oversteering. Furthermore, the large velocity of the slingshot motion enables bacteria to move efficiently through environments that contain shear-thinning viscoelastic fluids, such as the extracellular polymeric substances (EPS) that bacteria secrete on surfaces during biofilm formation.
Footnotes
↵1F.J. and J.C.C. contributed equally to this work.
↵2Present address: CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, and Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui Province 230026, People’s Republic of China.
- ↵3To whom correspondence should be addressed. E-mail: gclwong{at}seas.ucla.edu.
Author contributions: G.C.L.W. designed research; F.J. performed research; F.J., J.C.C., and M.L.G. analyzed data; and F.J., J.C.C., and G.C.L.W. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission. B.C. is a guest editor invited by the Editorial Board.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1105073108/-/DCSupplemental.
Bacteria use type-IV pili to slingshot on surfaces
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