Capsule

Definition

A capsule is a protective, gelatinous layer that surrounds the cell wall of some prokaryotes. It helps bacteria evade the host immune system and adhere to surfaces.

5 Must Know Facts For Your Next Test

1. Capsules are composed primarily of polysaccharides.
2. They play a crucial role in bacterial virulence by protecting cells from phagocytosis.
3. Capsules can prevent desiccation (drying out) of bacterial cells.
4. The presence of a capsule can be detected using special staining techniques in microbiology labs.
5. Not all bacteria have capsules; it is a characteristic feature of certain pathogenic species like Streptococcus pneumoniae.

Review Questions

• What is the primary composition of bacterial capsules?
• How do capsules contribute to bacterial virulence?
• Why might a capsule be advantageous for bacteria in harsh environments?

Related terms

Cell Wall: Provides structural support and shape to the cell, located beneath the capsule in some bacteria.

Flagella:

Long, whip-like structures used for movement by many prokaryotic cells.

Biofilm: A complex community of microorganisms adhering to surfaces, often protected by an extracellular matrix including polysaccharides.