Final answer:
Some bacteria evade complement by altering their surface proteins, like the M protein in Streptococcus, or by producing protective substances such as mycolic acid in Mycobacterium tuberculosis. Antigenic variation and proteases are other ways bacteria avoid immune detection and destruction.
Step-by-step explanation:
An unusual mechanism used by some bacteria to evade complement is to alter their surface proteins or to produce substances that interfere with the immune response. For instance, the fimbriae of certain species of Streptococcus contain M protein, inhibiting phagocytosis by blocking the binding of complement molecules. Furthermore, Mycobacterium tuberculosis produces a waxy substance called mycolic acid, which enables it to resist killing mechanisms within the phagolysosome after being engulfed by phagocytes.
Another method is antigenic variation, where pathogens alter surface proteins to avoid recognition by the immune system, exemplified by Borrelia burgdorferi and Neisseria gonorrhoeae. Additionally, some pathogens produce proteases that digest the antibody molecules, thereby combating antibody-mediated killing. These strategies exemplify the advanced methods bacteria use to survive and persist within their hosts, illustrating the constant battle between pathogens and the immune system.