<microbiology> Thick gel like material attached to the wall of gram-positive or gram-negative bacteria, giving colonies a smooth appearance. May contribute to pathogenicity by inhibiting phagocytosis. Mostly composed of very hydrophilic acidic polysaccharide, but considerable diversity exists.

<pathology> Cellular response in invertebrate animals to a foreign body too large to be phagocytosed. A multicellular aggregate of haemocytes or coelomocytes isolates the foreign object. In some insects the capsule is apparently acellular and composed of melanin.

(08 Oct 1997)