A chain mechanism for flagellum growth

Area of Science:

• Microbiology
• Biophysics
• Molecular Biology

Background:

• Bacterial flagella are essential for motility.
• Flagella assemble from protein subunits exported across the cell membrane.
• The mechanism for sustained flagellar growth is not fully understood.

Purpose of the Study:

• To elucidate the physical mechanism driving bacterial flagellar growth.
• To explain how constant subunit transit is maintained in the flagellar channel.
• To identify the energy source for flagellar assembly.

Main Methods:

• Investigated the physical mechanism of flagellar growth.
• Analyzed subunit interactions and linkage within the flagellar channel.
• Used thermodynamic analysis and polymer theory.
• Isolated flagella from bacterial cells to observe subunit chains.

Main Results:

• Proposed a mechanism harnessing the entropic force of unfolded subunits.
• Demonstrated head-to-tail linkage of subunits forming a pulling chain.
• Observed the predicted subunit chain within the flagellar transit channel.
• Confirmed that entropic forces drive subunit translocation and maintain growth rate.

Conclusions:

• Bacterial flagellar growth is driven by the entropic force of subunits.
• A self-assembling chain of linked subunits powers flagellar elongation.
• This mechanism ensures a constant rate of subunit delivery to the growing flagellum tip.