Which statement correctly describes Gram-positive bacteria after staining?

Which statement correctly describes Gram-positive bacteria after staining?

• A. Purple -- Thick cell wall
• B. Pink -- Thin cell wall
• C. Blue -- No cell wall
• D. Green -- Variable color

Answer: (A)

Gram staining separates bacteria by how their cell walls interact with the dye. Gram-positive cells have a thick peptidoglycan layer that traps the crystal violet–iodine complex during the stain procedure, and the alcohol step doesn’t remove it, so these cells stay purple under the microscope. In contrast, Gram-negative bacteria have a thinner peptidoglycan layer and an outer membrane; the alcohol decolorizes them and they take up the pink counterstain, appearing pink. Therefore, purple coloration with a thick cell wall is the correct description for Gram-positive bacteria after staining. The pink color describes Gram-negative cells, the idea of no cell wall isn’t correct for typical bacteria stained this way, and a green or variable color isn’t standard for Gram staining.

Gram staining separates bacteria by how their cell walls interact with the dye. Gram-positive cells have a thick peptidoglycan layer that traps the crystal violet–iodine complex during the stain procedure, and the alcohol step doesn’t remove it, so these cells stay purple under the microscope. In contrast, Gram-negative bacteria have a thinner peptidoglycan layer and an outer membrane; the alcohol decolorizes them and they take up the pink counterstain, appearing pink. Therefore, purple coloration with a thick cell wall is the correct description for Gram-positive bacteria after staining. The pink color describes Gram-negative cells, the idea of no cell wall isn’t correct for typical bacteria stained this way, and a green or variable color isn’t standard for Gram staining.