Dynamic stiffening of the flagellar hook

Area of Science:

• Microbiology
• Biophysics
• Molecular Biology

Background:

• Bacterial motility is powered by flagella, driven by a rotary motor.
• The flagellar hook acts as a universal joint, connecting the motor to the flagellum.
• Hook flexibility is essential for coordinated flagellar bundling in multi-flagellated bacteria.

Purpose of the Study:

• To investigate how the bacterial flagellar hook achieves dual functionality: flexibility for bundling and rigidity for force resistance.
• To elucidate the mechanical properties of the hook under dynamic conditions.

Main Methods:

• High-resolution measurements of hook fluctuations.
• Analysis of hook behavior under dynamical conditions.

Main Results:

• The bacterial flagellar hook exhibits strain-stiffening behavior.
• Hook bending stiffness dynamically increases with increasing torsional stress.

Conclusions:

• The hook's strain-stiffening property allows it to be compliant for bundle formation and rigid under high hydrodynamic loads.
• This mechanism enables efficient, high-speed bacterial motility.