Glycocalyx (mucilage sheath) is the outermost layer of the bacterial cell envelope which consists of non-cellulosic polysaccharides with or without proteins. It may occur in the form of loose sheath, called slime layer. If it is a thick covering, it is called capsule. Glycocalyx gives sticky character to the cell and is not absolutely essential for survival of bacteria. It prevents desiccation, protects from phagocytes, toxic chemicals and viruses and serves in attachment. It may give selective advantage though in certain situations