Negative staining is useful for what purpose?

Negative staining is useful for what purpose?

• A. Stains the bacteria heavily
• B. Stains the background and leaves bacteria unstained
• C. Stains only Gram-positive bacteria
• D. Masks cell morphology

Answer: (B)

Negative staining uses an acidic dye that carries a negative charge; bacterial surfaces are also negatively charged, so the dye is repelled by the cells and stains the surrounding medium instead. The result is bacteria that appear light against a dark background, making it easy to see their shape and size without distorting them. This approach is especially helpful for observing delicate cells and for revealing capsules as a clear halo around the organism, since the cells themselves aren’t heavily stained or heat-fixed.

Negative staining uses an acidic dye that carries a negative charge; bacterial surfaces are also negatively charged, so the dye is repelled by the cells and stains the surrounding medium instead. The result is bacteria that appear light against a dark background, making it easy to see their shape and size without distorting them. This approach is especially helpful for observing delicate cells and for revealing capsules as a clear halo around the organism, since the cells themselves aren’t heavily stained or heat-fixed.