Final answer:
Negative staining utilizes acidic dyes like acid fuchsin and eosin due to their negatively charged chromophores, which are repelled by the cell walls, allowing a clear view of cell outlines without penetration.
Step-by-step explanation:
Negative staining techniques in microscopy utilize acidic dyes because the negatively charged chromophores in these dyes are repelled by the negatively charged cell walls. This repulsion leads to the stain not being absorbed by the cells but by the surrounding space, creating a silhouette or contrast that defines the shape and size of the microorganisms against a dark background. By not coloring the cells themselves, negative staining avoids distorting the cell's shape and size, which could potentially happen with positive staining due to the interaction of the dye with the cell components.
Two examples of acidic dyes commonly used in negative staining are acid fuchsin and eosin. Both of these dyes have negatively charged chromophores that do not penetrate the cell, making them ideal for creating a clear visual contrast in microscopic analysis.