Final answer:
Bacterial capsules protect the bacteria by preventing phagocytosis and making it harder for immune cells to engulf them, while other virulence factors such as mycolic acid and M protein also help bacteria evade the immune response.
Step-by-step explanation:
Bacterial capsules serve as virulence factors by protecting bacteria from the host's immune system, particularly from being phagocytized by leukocytes or white blood cells. Capsules act as a protective barrier that hides the bacteria from the immune cells. Additionally, the size increase due to the capsule makes it more difficult for phagocytes to engulf the bacterial cell.
Other virulence factors that bacteria may use to evade the immune system include the production of substances like mycolic acid, as in the case of Mycobacterium tuberculosis, which allows it to resist killing mechanisms within the phagolysosome, and M protein in Streptococcus, which blocks binding of complement molecules needed for effective phagocytosis. Proteases that degrade host antibodies and mechanisms to inhibit the development of a phagolysosome after the bacteria has been phagocytized are also virulence strategies employed by bacteria to survive within the host.