Following an endospore stain, how can endospores be distinguished from vegetative cells under the microscope?

• A. Endospores appear red, while vegetative cells appear green.
• B. Endospores appear blue, while vegetative cells appear yellow.
• C. Endospores appear colorless, while vegetative cells appear purple.
• D. Endospores appear green, while vegetative cells appear pink or red.

Answer: (D)

Verified step by step guidance

1. Understand the principle behind the endospore stain, which is a differential staining technique used to distinguish endospores from vegetative cells based on their different chemical and structural properties.
2. Recall that the primary stain used in the endospore staining procedure is malachite green, which penetrates the tough outer coat of the endospore and stains it green.
3. Recognize that after staining with malachite green, a decolorizing step (usually water) is applied, which removes the stain from vegetative cells but not from the endospores due to their resistant coat.
4. Apply the counterstain, typically safranin, which stains the now colorless vegetative cells pink or red, providing a clear contrast to the green endospores.
5. Conclude that under the microscope, endospores appear green because they retain the malachite green stain, while vegetative cells appear pink or red due to the safranin counterstain.