Capsule Stain. The capsule stain employs an acidic stain and a basic stain to detect capsule production. Capsules are formed by organisms such as Klebsiella pneumoniae. Most capsules are composed of polysaccharides, but some are composed of polypeptides. The capsule differs from the slime layer that most bacterial cells produce in that it is a thick, detectable, discrete layer outside the cell wall. Some capsules have well-defined boundaries, and some have fuzzy, trailing edges.