Endospore staining

Endospore staining is a differential staining technique that distinguishes bacterial endospores from vegetative cells, commonly using heat to drive malachite green into spores and safranin to counterstain vegetative cells.

Schaeffer–Fulton method: A differential endospore staining protocol that uses heated malachite green and a safranin counterstain. This standard protocol supplies the heat and dye sequence used in endospore staining.
Sporulation: The process by which certain bacteria form dormant endospores under unfavorable conditions. Sporulation creates the structure that the staining procedure detects.
Bacterial identification: The laboratory process of determining which bacterial species or groups are present in a sample. Spore presence and position can narrow identification among bacterial isolates.
Gram staining: A differential staining method that separates bacteria by cell-envelope properties into Gram-positive and Gram-negative groups. It classifies cell-envelope behavior, whereas endospore staining directly highlights spores.
Malachite green: A synthetic green dye used as a biological stain and as a colorant. Heating helps this primary stain enter endospores, where it remains after rinsing.
Vegetative cell: The metabolically active, growing form of a microorganism, as opposed to a dormant or resistant form. It takes the counterstain rather than retaining malachite green after rinsing.
Bacillus subtilis: A Gram-positive, rod-shaped bacterium that forms endospores and is widely used in research. Its spores are a familiar model for demonstrating the staining technique.
Acid-fast staining: A differential staining method that identifies bacteria with waxy, mycolic-acid-rich cell envelopes. Its target is a distinctive cell wall, not a dormant spore structure.
Safranin: A red synthetic dye commonly used as a biological counterstain. It colors vegetative cells after water removes malachite green from them.
Bacillus: A genus of rod-shaped, endospore-forming bacteria that includes many soil-dwelling species. Bacillus species are common examples in teaching demonstrations of endospore staining.

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