Final answer:
Gram-negative cells primarily hold a) safranin in the gram stain process, resulting in a pink coloration, whereas Gram-positive cells retain the crystal violet dye and appear purple.
Step-by-step explanation:
The student asked about which dye gram-negative cells primarily hold in the gram stain process. The answer to this question is a) Safranin.
During the Gram staining procedure, after the crystal violet dye and Gram's iodine are applied, Gram-negative cells are decolorized by an alcohol wash, releasing the crystal violet dye.
These cells are then stained pink by the safranin. This secondary counterstain is less visible on Gram-positive cells as they retain the crystal violet dye due to their thicker peptidoglycan layers and appear purple.
Gram staining differentiates between two types of bacteria based on their cell wall structure: Gram-positive and Gram-negative.
It relies on the fact that Gram-negative cells have thinner peptidoglycan layers and an outer membrane that dissolves during the alcohol wash, allowing the crystal violet dye to escape and the pink dye safranin to stain the cells.
On the other hand, Gram-positive cells resist the decolorization process and retain the purple color of the crystal violet dye.