Load-dependent adaptation near zero load in the bacterial flagellar motor

Area of Science:

• Bacterial Physiology
• Molecular Motors
• Biophysics

Background:

• The bacterial flagellar motor is an ion-powered protein complex enabling bacterial motility.
• Stator units within the motor are crucial for torque generation and are suggested to employ a 'catch bond' mechanism for load adaptation.

Purpose of the Study:

• To develop a method for measuring single motor-stator unit dynamics under varying external loads.
• To investigate the load-dependent behavior of the bacterial flagellar motor and its stator units.

Main Methods:

• Utilized superparamagnetic beads attached to the flagellar hook for precise motor control.
• Employed a rotating magnetic field to manipulate motor speed across four levels.
• Tested motor dynamics under two distinct ion-motive force (IMF) conditions.

Main Results:

• Enabled measurement of single motor-stator unit dynamics across a wide load range, including near zero-torque conditions.
• Allowed separation of motor properties like rotation speed and IMF to analyze their effect on torque.
• Provided a framework for deeper exploration of load-dependent remodeling mechanisms.

Conclusions:

• The developed method offers a novel approach to dissecting the complex mechanics of the bacterial flagellar motor.
• Findings contribute to understanding how bacterial motors adapt to external forces, potentially via mechanosensitive stator units.