title: Physical properties of Escherichia coli P pili measured by optical tweezers.
abstract: 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 approximately 10(3) 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 approximately 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.
authors.affiliation: Department of Microbiology and Immunology, The Lawson Health Research Institute, University of Western Ontario, London, Ontario, N6A 4V2, Canada.
authors.forename: Jana
authors.initials: J
authors.lastname: Jass
authors.forename: Staffan
authors.initials: S
authors.lastname: Schedin
authors.forename: Erik
authors.initials: E
authors.lastname: Fällman
authors.forename: Jörgen
authors.initials: J
authors.lastname: Ohlsson
authors.forename: Ulf J
authors.initials: UJ
authors.lastname: Nilsson
authors.forename: Bernt Eric
authors.initials: BE
authors.lastname: Uhlin
authors.forename: Ove
authors.initials: O
authors.lastname: Axner
mesh_terms: D001422:Bacterial Adhesion / Q000502:physiology*; D018929:Cell Culture Techniques / Q000379:methods; D003198:Computer Simulation; D004548:Elasticity; D004926:Escherichia coli / Q000166:cytology* / Q000502:physiology*; D010861:Fimbriae, Bacterial / Q000502:physiology* / Q000648:ultrastructure*; D007834:Lasers; D008846:Micromanipulation / Q000379:methods*; D008954:Models, Biological; D010812:Physical Stimulation / Q000379:methods; D013718:Tensile Strength