Composition
It usually consists of polysaccharides, but can be composed of other materials (e.g., polypeptide in B. anthracis). Because most capsules are water soluble, they are difficult to stain using standard stains because most stains do not adhere to the capsule. For examination under the microscope, the bacteria and their background are stained darker than the capsule, which doesn't stain. When viewed, bacterial cells as well as the surface they are on, are stained dark, while the capsule remains pale or colorless and appears as a ring around the cell.
Read more about this topic: Bacterial Capsule
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