Which of the following best describes a key structural feature of the cell envelope in Gram-positive bacteria?

• A. An outer membrane containing lipopolysaccharides
• B. A thin peptidoglycan layer sandwiched between two membranes
• C. The presence of periplasmic space with high enzyme concentration
• D. A thick peptidoglycan layer outside the cell membrane

Answer: (D)

Verified step by step guidance

1. Understand that the cell envelope of bacteria consists of the cell membrane and the cell wall, which varies between Gram-positive and Gram-negative bacteria.
2. Recall that Gram-positive bacteria have a thick peptidoglycan layer, which provides structural support and retains the crystal violet stain during Gram staining.
3. Note that Gram-positive bacteria lack an outer membrane, which is a feature characteristic of Gram-negative bacteria and contains lipopolysaccharides (LPS).
4. Recognize that the periplasmic space is more prominent in Gram-negative bacteria, located between the outer membrane and the plasma membrane, and contains enzymes and transport proteins.
5. Conclude that the key structural feature of Gram-positive bacteria is a thick peptidoglycan layer located outside the cell membrane, without an outer membrane or significant periplasmic space.