Which statement correctly describes Gram-negative bacteria?

Which statement correctly describes Gram-negative bacteria?

• A. Thin peptidoglycan layer; has outer membrane; stains pink; much periplasm; has LPS; doesn't contain teichoic acid
• B. Thick peptidoglycan layer; lacks outer membrane; stains purple; little periplasm; no LPS; contains teichoic acid
• C. Thin peptidoglycan layer; has outer membrane; stains purple; little periplasm; has LPS; contains teichoic acid
• D. Thick peptidoglycan layer; has outer membrane; stains pink; much periplasm; has LPS; lacks teichoic acid

Answer: (A)

Gram-negative bacteria have a thin peptidoglycan layer and an external outer membrane that contains lipopolysaccharide. This envelope design creates a relatively large periplasmic space. During Gram staining, the thin peptidoglycan and the outer membrane do not retain the crystal violet–iodine complex after the decolorization step, so the cells take up the pink counterstain. They also lack teichoic acids, which are characteristic of Gram-positive walls. So the best description is a thin peptidoglycan layer with an outer membrane, pink staining, substantial periplasm, presence of LPS, and absence of teichoic acid.

Gram-negative bacteria have a thin peptidoglycan layer and an external outer membrane that contains lipopolysaccharide. This envelope design creates a relatively large periplasmic space. During Gram staining, the thin peptidoglycan and the outer membrane do not retain the crystal violet–iodine complex after the decolorization step, so the cells take up the pink counterstain. They also lack teichoic acids, which are characteristic of Gram-positive walls. So the best description is a thin peptidoglycan layer with an outer membrane, pink staining, substantial periplasm, presence of LPS, and absence of teichoic acid.