Encapsulated organisms are difficult to directly stain because:

• A. they lack a cell wall, preventing stain uptake
• B. their metabolic activity destroys the stain
• C. their capsules are composed of polysaccharides that repel most stains
• D. they are too small to retain any stain

Answer: (C)

Verified step by step guidance

1. Understand what an encapsulated organism is: it is a microorganism surrounded by a capsule, which is a gelatinous layer outside the cell wall.
2. Recognize that the capsule is primarily composed of polysaccharides, which are complex sugar molecules.
3. Recall that polysaccharides are hydrophilic and have a neutral or negative charge, which causes them to repel many common stains used in microbiology.
4. Note that because the capsule repels stains, it does not readily take up dyes during direct staining procedures, making it difficult to visualize using standard staining techniques.
5. Conclude that the difficulty in staining encapsulated organisms is due to the chemical nature of their capsules, not because they lack a cell wall, destroy stains, or are too small to retain stains.