Final answer:
The capsule of virulent bacteria like S. pneumoniae and B. anthracis provides protection from the immune system by preventing phagocytosis and making bacteria more resistant to immune responses. Other virulence factors also aid in immune evasion.
Step-by-step explanation:
The capsule plays a critical role in the virulence of certain bacteria, such as Streptococcus pneumoniae and Bacillus anthracis, which can cause pneumonia and anthrax, respectively. The capsule protects these bacteria from the immune system in two main ways:
- It prevents phagocytic cells from adhering to the bacteria, making it difficult for these immune cells to engulf and destroy the pathogen.
- If the bacteria are ingested by phagocytes, the capsule can make the bacterial cell larger and more resistant to the killing mechanisms within the phagocytes, thereby inhibiting effective phagocytosis.
In addition to the capsule, other virulence factors like proteases, M protein in Streptococcus, and mycolic acid in Mycobacterium tuberculosis, also help bacteria evade the immune system.