The architecture, assembly, and evolution of a complex flagellar motor

Area of Science:

• Microbiology
• Evolutionary Biology
• Structural Biology

Background:

• Bacterial flagella are crucial for motility, with knowledge primarily from simple models like E. coli.
• Most flagellated bacteria have complex, species-specific motors that are poorly understood.
• The evolution and assembly mechanisms of complex flagellar motors remain largely unexplored.

Purpose of the Study:

• To build a near-complete model of the Campylobacter jejuni flagellar motor.
• To elucidate the complex architecture, composition, and function of this motor.
• To investigate the evolutionary origins of complex flagellar motor components.

Main Methods:

• Multidisciplinary approach combining structural and evolutionary analyses.
• Near-complete model construction of the Campylobacter jejuni flagellar motor.
• In-depth evolutionary analyses of flagellar components.

Main Results:

• Identification of an E-ring, a periplasmic cage with two conformations, and an intricate E-ring/cage interaction network.
• Demonstration of critical roles for these scaffolds in stabilizing and regulating 17 torque-generating stator complexes.
• Uncovering the ancient origin of the E-ring and exaptation of type IV pili components in Campylobacterota.

Conclusions:

• Novel mechanisms for assembly and function in complex bacterial flagellar motors have been revealed.
• The study provides insights into the evolution of flagella and the diversification of bacterial species.
• The findings highlight the complexity and adaptability of bacterial motility systems.