Streptococcus pneumoniae capsular material is composed of polysaccharide. The capsule is the pathogen's most important determinant of virulence because it allows the bacterial cells to escape phagocytes in the lung.
Bacillus anthracis capsule is composed of poly-D-glutamic acid. Its capsule is antiphagocytic, and it protects the bacteria from complement-mediated lysis in serum or blood.
The capsule of Streptococcus pyogenes is composed of hyaluronic acid, the same polymer as found in human connective tissue. The capsule is an antigenic disguise that prevents recognition of the streptococci by phagocytes or the immune system.