Final answer:
The primary stain used in the Schaeffer-Fulton staining method
a) Methylene blue
Step-by-step explanation:
In the Schaeffer-Fulton staining method, the primary stain utilized is Methylene blue. This method involves staining bacterial endospores within a sample. Methylene blue serves as the primary stain due to its affinity for the endospore structures, imparting a distinct color to the endospores, while the counterstain, Safranin, is used to color vegetative cells.
The Schaeffer-Fulton staining technique is a two-step process where malachite green initially stains the endospores, which are then decolorized using water and counterstained with Safranin. However, in the Schaeffer-Fulton modification of the method, Methylene blue replaces malachite green as the primary stain. This adjustment ensures a more efficient differentiation between endospores and vegetative cells, facilitating clearer microscopic examination.
Methylene blue, with its positively charged chromophore, adheres preferentially to the negatively charged structures present in endospores. This staining method aids in distinguishing between the dormant endospores and the active vegetative cells in a bacterial sample, offering valuable insights into the microbiological characteristics being studied.