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Dynamic force spectroscopy of E. coli P pili.
Magnus Andersson1, Erik Fällman, Bernt Eric Uhlin
1Department of Physics and Department of Molecular Biology, Umeå University, Umeå, Sweden.
Biophysical Journal
|July 18, 2006
Summary
Escherichia coli pili, crucial for urinary tract infections, exhibit unique elongation properties. Dynamic force spectroscopy reveals their unfolding behavior, providing insights into bacterial adhesion mechanisms under shear forces.
Area of Science:
- Microbiology
- Biophysics
- Structural Biology
Background:
- Surface organelles called pili on Escherichia coli mediate bacterial adhesion, particularly in urinary tract infections.
- These pili possess remarkable elongation properties, enabling close bacterium-host contact despite urine flow shear forces.
Purpose of the Study:
- To investigate the elongation properties of P pili from Escherichia coli under low elongation speeds using dynamic force spectroscopy.
- To develop and verify a kinetic model for the unfolding of the helixlike chain structure of P pili.
Main Methods:
- Dynamic force spectroscopy was employed to probe the behavior of P pili.
- A kinetic model was derived and verified to describe the unfolding of the quaternary structure of the PapA rod.
Main Results:
- Pili unfolding occurred at a constant force, largely independent of elongation speed for slow speeds (up to ~0.4 µm/s).
- Faster elongations showed a dynamic response with logarithmic dependence, revealing energy landscape and reaction rates.
- Layer-to-layer bond properties were quantified: bond length (~0.76 nm), opening rate (~0.8 Hz), and closure rate (~8 GHz).
Conclusions:
- The study elucidates the mechanical behavior and unfolding kinetics of P pili, crucial for understanding bacterial adhesion.
- Results support a sticky-chain model for PapA rod elongation, extending previous steady-state findings.
- This research provides critical data on the energy landscape and bond dynamics of bacterial pili.