Which statement correctly links Gram-negative bacteria to its observed color after staining?

Which statement correctly links Gram-negative bacteria to its observed color after staining?

• A. Purple -- Thick cell wall
• B. Pink -- Thin cell wall
• C. Blue -- Thin cell wall
• D. Green -- Variable color

Answer: (B)

Gram staining differentiates bacteria by cell wall structure: organisms with a thick peptidoglycan layer retain the crystal violet and appear purple, while those with a thin peptidoglycan layer plus an outer membrane do not retain the dye after decolorization and take up the counterstain to appear pink. This means the link between pink color and a thin cell wall correctly describes Gram-negative bacteria. The purple option corresponds to thick peptidoglycan typical of Gram-positive bacteria, and blue or green are not standard outcomes of the Gram stain.

Gram staining differentiates bacteria by cell wall structure: organisms with a thick peptidoglycan layer retain the crystal violet and appear purple, while those with a thin peptidoglycan layer plus an outer membrane do not retain the dye after decolorization and take up the counterstain to appear pink. This means the link between pink color and a thin cell wall correctly describes Gram-negative bacteria. The purple option corresponds to thick peptidoglycan typical of Gram-positive bacteria, and blue or green are not standard outcomes of the Gram stain.