What property allows Gram-positive cells to retain crystal violet-iodine complex after the decolorization step?

What property allows Gram-positive cells to retain crystal violet-iodine complex after the decolorization step?

• A. Outer membrane
• B. Thick peptidoglycan layer
• C. Capsule presence
• D. Flagella

Answer: (B)

Retaining the crystal violet-iodine complex hinges on the structure of the Gram-positive cell wall. Their thick peptidoglycan layer forms a dense, rigid matrix that traps the large crystal violet-iodine complex during the decolorization step. The alcohol decolorizes by affecting lipids and dissolving outer membranes, but in Gram-positive cells the thick, highly cross-linked peptidoglycan doesn’t lose the trapped dye, so the purple stain remains. Capsule presence or flagella don’t contribute to this retention, and the outer membrane is not a feature of Gram-positive walls.

Retaining the crystal violet-iodine complex hinges on the structure of the Gram-positive cell wall. Their thick peptidoglycan layer forms a dense, rigid matrix that traps the large crystal violet-iodine complex during the decolorization step. The alcohol decolorizes by affecting lipids and dissolving outer membranes, but in Gram-positive cells the thick, highly cross-linked peptidoglycan doesn’t lose the trapped dye, so the purple stain remains. Capsule presence or flagella don’t contribute to this retention, and the outer membrane is not a feature of Gram-positive walls.