Capsules

Definition

Capsules are gelatinous outer layers surrounding some bacteria, providing protection and aiding in pathogenicity. They are composed primarily of polysaccharides or polypeptides.

5 Must Know Facts For Your Next Test

1. Capsules enhance bacterial virulence by preventing phagocytosis by host immune cells.
2. Capsules can be visualized using negative staining techniques such as India ink or Nigrosin.
3. The presence of a capsule can help in the identification and classification of bacterial species.
4. Encapsulated bacteria are often more resistant to desiccation and harsh environmental conditions.
5. Some vaccines target capsular polysaccharides to provide immunity against certain pathogenic bacteria.

Review Questions

• How do capsules contribute to the virulence of bacterial pathogens?
• What staining technique is commonly used to visualize bacterial capsules?
• Why are encapsulated bacteria generally more resistant to environmental stress?

Related terms

Phagocytosis:

The process by which cells engulf and digest foreign particles or microorganisms.

Negative Staining: A microscopy technique that stains the background but leaves the specimen unstained, useful for observing capsules.

Polysaccharides:

Complex carbohydrates composed of long chains of monosaccharide units, often forming structural components like bacterial capsules.