Capsule

Definition

A capsule is a dense and well-defined layer of polysaccharides or proteins that surrounds the cell wall of some prokaryotic cells. It provides protection against environmental hazards and plays a role in pathogenicity.

5 Must Know Facts For Your Next Test

1. Capsules help bacteria evade the host's immune system by preventing phagocytosis.
2. They are often composed of polysaccharides, but can also be made of polypeptides.
3. Capsules can enhance the virulence of pathogenic bacteria, making them more effective at causing disease.
4. The presence of a capsule can be detected using special staining techniques, such as the India ink method.
5. Some vaccines target bacterial capsules to induce immunity against specific pathogens.

Review Questions

• What is the primary function of a bacterial capsule?
• How does a capsule contribute to the pathogenicity of bacteria?
• Which staining technique is commonly used to visualize bacterial capsules?

Related terms

Biofilm: A complex community of microorganisms that adhere to surfaces and are embedded in a self-produced extracellular matrix.

Glycocalyx: A glycoprotein and glycolipid covering that surrounds some cells, providing protection and aiding in cell communication.

Phagocytosis: The process by which certain living cells called phagocytes ingest or engulf other cells or particles.