Why is steam used during the endospore staining procedure?

• A. To fix the stain to the glass slide
• B. To decolorize vegetative cells
• C. To drive the primary stain into the resistant endospore coat
• D. To prevent the formation of endospores during staining

Answer: (C)

Verified step by step guidance

1. Understand the nature of endospores: Endospores have a tough, resistant outer coat that makes them impermeable to many stains under normal conditions.
2. Recognize the role of the primary stain in endospore staining, which is usually malachite green, a dye that needs to penetrate the endospore coat to stain it effectively.
3. Identify why steam is applied during the staining process: Steam acts as a mordant by heating the slide, which helps to soften or loosen the endospore coat, allowing the primary stain to penetrate deeply.
4. Note that steam is not used to fix the stain to the glass slide, nor is it used to decolorize vegetative cells or prevent endospore formation; its main function is to facilitate stain entry into the endospore.
5. Conclude that the use of steam is essential to drive the primary stain into the resistant endospore coat, ensuring that endospores can be visualized under the microscope.