Protein which is part of a capsule, the protective structure surrounding some bacteria or fungi. The bacterial capsule is a layer of material, usually polysaccharide, attached to the cell wall possibly via covalent attachments to either phospholipid or lipid-A molecules. It has several functions: promote bacterial adhesion to surfaces or interaction with other organisms; act as a permeability barrier, as a defense mechanism against phagocytosis and/or as a nutrient reserve. Among pathogens, capsule formation often correlates with pathogenicity. The fungal capsule is an extracellular layer which lies outside the cell wall and it is usually composed of polysaccharides. It protects the cell from different environmental dangers such as phagocytosis, dessication, etc.