Lecture Notes on Bacterial Flagella

Introduction

• Speaker: Dr. L
• Topic: Basics of flagella structure, function, and motility in bacteria

Importance of Flagella

• Flagella allow bacteria to move in unique ways
• Example shown: Flagella stained Proteus vulgaris

Structure of Flagella

• Common Components:
  • Filament: Main structural component
  • Hook: Connects filament to basal body
  • Basal Body: Site of rotation
• Mechanism of Action:
  • Operates via rotary motion
  • Rotation is driven by the flow of hydrogen ions/protons, similar to ATP synthase in the electron transport system

Differences in Gram-Positive and Gram-Negative Bacteria

• Gram-Positive:
  • Simpler structure due to a thick cell wall
• Gram-Negative:
  • More complex due to the presence of a periplasmic space and outer membrane

Bacterial Movement

• Methods of Movement:
  • Run: Movement in one direction for a long duration
    • Achieved through counterclockwise rotation of flagella
  • Tumble: Rapid stop and change in direction
    • Caused by changing flagella rotation from counterclockwise to clockwise

Reasons for Bacterial Motility

• Attractants and Repellents:
  • Move towards attractants (e.g., food, oxygen) - termed as chemotaxis
  • Move away from repellents (e.g., waste products)
  • Phototaxis: Movement towards or away from light

Conclusion

• Bacteria use flagella for motility to move towards desired conditions and away from undesirable ones.
• The run and tumble mechanism allows them to efficiently navigate their environment.

Have a wonderful day and be blessed!