Visualization of Flagella during bacterial Swarming

Area of Science:

• Microbiology
• Cell Biology
• Biophysics

Background:

• Escherichia coli motility in liquid media is well-understood.
• Swarming behavior in Escherichia coli involves cell elongation, increased flagella production, and coordinated movement in a thin fluid film.
• Swarming occurs in a complex, confined environment with distinct upper and lower surfaces.

Purpose of the Study:

• To investigate the trajectories of swarming Escherichia coli cells.
• To elucidate the role of flagellar motion in determining swarming cell trajectories.
• To differentiate and describe various types of cell movement during swarming.

Main Methods:

• Phase-contrast microscopy to visualize cell bodies.
• Fluorescence microscopy to visualize flagellar filaments.
• Analysis of cell trajectories during swarming on agar surfaces.

Main Results:

• Four distinct track types were identified: stalls, reversals, lateral movement, and forward movement.
• Flagellar filament extension is crucial for fluid movement during stalls at colony edges.
• Changes in flagellar filament chirality are critical for reversal maneuvers.
• Lateral movement is influenced by adjacent cells, while forward movement utilizes flagellar bundle propulsion similar to free-swimming cells.

Conclusions:

• Flagellar dynamics are intricately linked to the diverse maneuvers observed in Escherichia coli swarming.
• Understanding these flagellar-driven movements provides insight into collective cell migration in confined environments.
• The study distinguishes specific roles of flagellar motion in different swarming behaviors.