title: Dynamic modulation of fimbrial extension and FimH-mannose binding force on live bacteria under pH changes: a molecular atomic force microscopy analysis.
abstract: Mechanical and conformational properties of type 1 fimbriae were evaluated on live bacterial cells by Single Molecule Force Spectroscopy (SMFS) and Dynamic Force Spectroscopy (DFS) in buffered solutions whose pH varied from 3 to 9. We evidenced that both fimbrial extension and fimbrial binding force to mannosylated-surface are modulated with changing the externally applied shear force and the solution pH. In particular, intertwined FimA-FimA and FimH-mannose interactions lead to a 5 to 25-fold decrease of the fimbrial unwinding for pulling rates larger than 10 μm/s and for pH values outside the range 5 to 7. In this pH range, the FimH-mannose binding force is maximal with a magnitude of -150-200 pN and the fimbriae extension reaches 8 μm. The enhancement of the FimH-mannose binding force at neutral pH, as evidenced from molecular AFM analyses, strongly correlates with an optimum in yeast agglutination detected at pH 5 to 7. The results reported in this work suggest that "catch bond effect" was negligible over the range of pulling rates tested, and both FimA-FimA and FimH-mannose interactions under given pH and external shear force conditions modify the ability of the bacteria to efficiently colonize host surfaces.
authors.forename: A
authors.initials: A
authors.lastname: Jacquot
authors.forename: C
authors.initials: C
authors.lastname: Sakamoto
authors.forename: A
authors.initials: A
authors.lastname: Razafitianamaharavo
authors.forename: C
authors.initials: C
authors.lastname: Caillet
authors.forename: J
authors.initials: J
authors.lastname: Merlin
authors.forename: A
authors.initials: A
authors.lastname: Fahs
authors.forename: J M
authors.initials: JM
authors.lastname: Ghigo
authors.forename: C
authors.initials: C
authors.lastname: Beloin
authors.forename: J F L
authors.initials: JF
authors.lastname: Duval
authors.forename: G
authors.initials: G
authors.lastname: Francius
mesh_terms: D018830:Adhesins, Escherichia coli / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D004926:Escherichia coli / Q000737:chemistry / Q000502:physiology* / Q000648:ultrastructure; D036781:Fimbriae Proteins / Q000737:chemistry / Q000378:metabolism*; D010861:Fimbriae, Bacterial / Q000737:chemistry / Q000502:physiology* / Q000648:ultrastructure; D006863:Hydrogen-Ion Concentration; D008358:Mannose / Q000737:chemistry / Q000378:metabolism*; D018625:Microscopy, Atomic Force / Q000379:methods*; D011485:Protein Binding; D013314:Stress, Mechanical
chemical_list: D018830:Adhesins, Escherichia coli; C058769:fimH protein, E coli; D036781:Fimbriae Proteins; D008358:Mannose