Which of the following is used to stain endospores?
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Associate stains with specific procedures: Crystal Violet and Safranin are key to Gram staining. Malachite Green and Safranin are key to endospore staining. This helps in quick recall during exams.
Step 1: Understanding the Concept:
The question asks to identify the primary stain used in the endospore staining procedure. Endospores are dormant, tough, and non-reproductive structures produced by some bacteria. Their tough outer coating makes them resistant to typical staining methods. Step 2: Detailed Explanation:
The most common method for staining endospores is the Schaeffer-Fulton method. This differential staining technique involves the following steps and reagents:
Primary Stain: Malachite green is applied to the bacterial smear. Heat is used as a mordant to force the stain into the resistant endospores. Both the vegetative cells and the endospores appear green at this stage.
Decolorizer: Water is used to wash the smear. The water-soluble malachite green is easily rinsed out from the vegetative cells but not from the endospores.
Counterstain: Safranin is applied. It stains the now colorless vegetative cells pink or red. The endospores retain the green color of the primary stain.
Let's look at the other options:
Safranin: Used as the counterstain in both Gram staining and endospore staining.
Crystal violet: Used as the primary stain in Gram staining.
Brilliant green: A different type of stain, often used as a selective agent in culture media.
Step 3: Final Answer:
Based on the standard Schaeffer-Fulton endospore staining protocol, malachite green is the specific primary stain used to color the endospores.
