An extracellular coating usually composed of mucopolysaccharides produced by some bacteria. May increase an organism’s virulence by interfering with the nonspecific immune system (phagocytosis) of the host.
A thick, gelatinous outer layer round a bacterium, composed of polysaccharides, proteins or polypeptides. Possession of a capsule is frequently linked with virulence, and the capsular material often determines the immunological species or sub-species concerned.
The polysaccharide or polypeptide layer that surrounds the cell wall of some bacteria; it provides resistance to phagocytosis. Capsules are antigenic. Their antigens are used to manufacture several common vaccines.