Describe the general principle of capsule staining and what a capsule appears as under the microscope.

• A. Capsules visible as purple inclusions.
• B. Negative staining highlights capsules around cells.
• C. Capsule appears as a clear halo around a stained cell.
• D. Capsules cannot be visualized.

Answer: (C)

Capsules are made of polysaccharides that don’t take up most stains, so visualization relies on staining that leaves the capsule uncolored while the cell is stained. In capsule staining, you either stain the background (negative stain) or stain the cell while the capsule remains unstained. The result is a clear, colorless halo surrounding a stained cell, which marks the capsule’s boundary. This halo appearance is why the capsule is described as a clear halo around the cell.