Physical Properties of Escherichia coli P Pili Measured by Optical Tweezers

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The mechanical behavior of individual P pili of uropathogenic Escherichia coli has been investigated using optical tweezers. P pili, whose main part constitutes the PapA rod, composed of 103 PapA subunits in a helical arrangement, are distributed over the bacterial surface and mediate adhesion to host cells. They are particularly important in the pathogenesis of E. coli colonizing the upper urinary tract and kidneys. A biological model system has been established for in situ measurements of the forces that occur during mechanical stretching of pili. A mathematical model of the force-versus-elongation behavior of an individual pilus has been developed. Three elongation regions of pili were identified. In region I, P pili stretch elastically, up to a relative elongation of 16 ± 3%. The product of elasticity modulus and area of a P pilus, EA, was assessed to 154 ± 20 pN (n = 6). In region II, the quaternary structure of the PapA rod unfolds under a constant force of 27 ± 2 pN (n 100) by a sequential breaking of the interactions between adjacent layers of PapA subunits. This unfolding can elongate the pilus up to 7 ± 2 times. In region III, pili elongate in a nonlinear manner as a result of stretching until the bond ruptures.


  • Jana Jass
  • Staffan Schedin
  • Erik Fällman
  • Jörgen Ohlsson
  • Ulf Nilsson
  • Bernt Eric Uhlin
  • Ove Axner
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Biophysics
Original languageEnglish
Pages (from-to)4271-4283
JournalBiophysical Journal
Issue number6
Publication statusPublished - 2004
Publication categoryResearch

Bibliographic note

The information about affiliations in this record was updated in December 2015. The record was previously connected to the following departments: Organic chemistry (S/LTH) (011001240)

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