Journal
EUROPEAN BIOPHYSICS JOURNAL WITH BIOPHYSICS LETTERS
Volume 39, Issue 8, Pages 1105-1115Publisher
SPRINGER
DOI: 10.1007/s00249-009-0552-8
Keywords
Fimbriae; Uropathogenic Escherichia coli; Bond breaking; Unfolding; Optical tweezers
Categories
Funding
- Swedish Research Council [CEE LSHB-CT-2005-512061]
- Kempe foundation
- Magnus Bergvall's foundation
- Fondation Pour La Recherche Medicale [SPE20071211235]
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S pili are members of the chaperone-usher-pathway-assembled pili family that are predominantly associated with neonatal meningitis (S-II) and believed to play a role in ascending urinary tract infections (S-I). We used force-measuring optical tweezers to characterize the intrinsic biomechanical properties and kinetics of S-II and S-I pili. Under steady-state conditions, a sequential unfolding of the layers in the helix-like rod occurred at somewhat different forces, 26 pN for S-II pili and 21 pN for S-I pili, and there was an apparent difference in the kinetics, 1.3 and 8.8 Hz. Tests with bacteria defective in a newly recognized sfa gene (sfaX (II)) indicated that absence of the sfaX (II) gene weakens the interactions of the fimbrium slightly and decreases the kinetics. Data of S-I are compared with those of previously assessed pili primary associated with urinary tract infections, the P and type 1 pili. S pili have weaker layer-to-layer bonds than both P and type 1 pili, 21, 28 and 30 pN, respectively. In addition, the S pili kinetics are similar to 10 times faster than the kinetics of P pili and similar to 550 times faster than the kinetics of type 1 pili. Our results also show that the biomechanical properties of pili expressed ectopically from a plasmid in a laboratory strain (HB101) and pili expressed from the chromosome of a clinical isolate (IHE3034) are identical. Moreover, we demonstrate that it is possible to distinguish, by analyzing force-extension data, the different types of pili expressed by an individual cell of a clinical bacterial isolate.
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