title: Fast uncoiling kinetics of F1C pili expressed by uropathogenic Escherichia coli are revealed on a single pilus level using force-measuring optical tweezers.
abstract: 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.
authors.affiliation: Department of Physics, Umeå University, SE-90187 Umeå, Sweden.
authors.forename: Mickaël
authors.initials: M
authors.lastname: Castelain
authors.forename: Sarah
authors.initials: S
authors.lastname: Ehlers
authors.forename: Jeanna
authors.initials: J
authors.lastname: Klinth
authors.forename: Stina
authors.initials: S
authors.lastname: Lindberg
authors.forename: Magnus
authors.initials: M
authors.lastname: Andersson
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*; D001696:Biomechanical Phenomena; D036781:Fimbriae Proteins / Q000032:analysis / Q000737:chemistry; D010861:Fimbriae, Bacterial / Q000737:chemistry* / Q000145:classification; D007700:Kinetics; D018625:Microscopy, Atomic Force / Q000379:methods; D008954:Models, Biological; D052898:Optical Tweezers; D017510:Protein Folding; D017433:Protein Structure, Secondary; D055672:Static Electricity; D013314:Stress, Mechanical; D014552:Urinary Tract Infections / Q000382:microbiology; D056689:Uropathogenic Escherichia coli / Q000737:chemistry* / Q000502:physiology / Q000648:ultrastructure*
chemical_list: D036781:Fimbriae Proteins