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Unfolding and refolding properties of S pili on extraintestinal pathogenic Escherichia coli

Mickaël Castelain1, Annika E Sjöström, Erik Fällman

  • 1Department of Physics, Umeå University, 901 87, Umea, Sweden.

European Biophysics Journal : EBJ
|November 4, 2009
PubMed

Insights

S pili, crucial for bacterial infections like meningitis and UTIs, exhibit distinct biomechanical properties. Their unique layer-to-layer bond strength and rapid kinetics differentiate them from other pili, offering insights into bacterial adhesion mechanisms.

Area of Science:

  • Microbiology
  • Biophysics
  • Bacterial Pathogenesis

Background:

  • S pili are part of the chaperone-usher-pathway-assembled pili family.
  • S(II) pili are linked to neonatal meningitis, while S(I) pili are implicated in urinary tract infections.
  • Understanding pili biomechanics is key to deciphering bacterial adhesion and infection.

Purpose of the Study:

  • To characterize the intrinsic biomechanical properties and kinetics of S(II) and S(I) pili.
  • To compare the biomechanics of S pili with other known pili involved in urinary tract infections (P and type 1 pili).
  • To investigate the role of the sfaX(II) gene in S pili function.

Main Methods:

  • Utilized force-measuring optical tweezers to probe the mechanical unfolding of S pili.
  • Analyzed force-extension data to determine layer-to-layer bond forces and unfolding kinetics.
  • Compared pili expressed from clinical isolates and laboratory strains.

Main Results:

  • S(II) and S(I) pili exhibit distinct unfolding forces (26 pN and 21 pN, respectively) and kinetics (1.3 Hz and 8.8 Hz).
  • S pili possess weaker layer-to-layer bonds compared to P and type 1 pili.
  • S pili display significantly faster kinetics than P and type 1 pili, and the sfaX(II) gene influences these properties.

Conclusions:

  • The biomechanical properties of S pili are unique and differ significantly from P and type 1 pili.
  • These distinct properties likely contribute to the specific roles of S pili in neonatal meningitis and urinary tract infections.
  • Optical tweezers provide a powerful method for distinguishing and characterizing different types of bacterial pili on individual cells.

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