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What is the difference between flagella and fimbriae?

Published in Microbial Structures 1 min read

The primary difference between flagella and fimbriae (also known as pili) lies in their function: flagella are primarily for locomotion, while fimbriae are mainly for adhesion.

Flagella vs. Fimbriae: A Detailed Comparison

Here's a more detailed breakdown of the differences between flagella and fimbriae in bacteria:

Feature Flagella Fimbriae (Pili)
Primary Function Locomotion (movement) Adhesion (attachment)
Structure Long, whip-like appendages Short, hair-like appendages
Location Can be polar (at one or both ends) or peritrichous (all over the surface) Cover the entire surface of the bacterium
Gram-Positive Bacteria Present and useful for identification Present
Gram-Negative Bacteria Present and useful for identification Present

Key Distinctions Explained

  • Function: As the reference states, flagella are organs of locomotion, meaning they enable bacteria to move. Fimbriae (or pili), on the other hand, are for adhesion.
  • Structure and Appearance: Flagella are longer and fewer in number compared to fimbriae. Fimbriae are shorter, thinner, and numerous, often described as hair-like structures covering the bacterial cell.

Examples

  • A bacterium using its flagella to swim towards a nutrient source.
  • E. coli using fimbriae to attach to the cells lining the urinary tract, causing a urinary tract infection.