Journal
EUROPEAN BIOPHYSICS JOURNAL WITH BIOPHYSICS LETTERS
Volume 40, Issue 3, Pages 305-316Publisher
SPRINGER
DOI: 10.1007/s00249-010-0648-1
Keywords
Bacterial adhesion; Dynamic force spectroscopy; Pili relaxation; Uncoiling; Bond kinetics
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Funding
- Swedish Research Council [621-2008-3280, 2007-3574]
- Kempe foundations
- Magnus Bergvall's foundation
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Uropathogenic Escherichia coli (UPEC) express various kinds of organelles, so-called pili or fimbriae, that mediate adhesion to host tissue in the urinary tract through specific receptor-adhesin interactions. The biomechanical properties of these pili have been considered important for the ability of bacteria to withstand shear forces from rinsing urine flows. Force-measuring optical tweezers have been used to characterize individual organelles of F1C type expressed by UPEC bacteria with respect to such properties. Qualitatively, the force-versus-elongation response was found to be similar to that of other types of helix-like pili expressed by UPEC, i.e., type 1, P, and S, with force-induced elongation in three regions, one of which represents the important uncoiling mechanism of the helix-like quaternary structure. Quantitatively, the steady-state uncoiling force was assessed as 26.4 +/- 1.4 pN, which is similar to those of other pili (which range from 21 pN for S-I to 30 pN for type 1). The corner velocity for dynamic response (1,400 nm/s) was found to be larger than those of the other pili (400-700 nm/s for S and P pili, and 6 nm/s for type 1). The kinetics were found to be faster, with a thermal opening rate of 17 Hz, a few times higher than S and P pili, and three orders of magnitude higher than type 1. These data suggest that F1C pili are, like P and S pili, evolutionarily selected to primarily withstand the conditions expressed in the upper urinary tract.
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