Which of the following structures is found in the cell wall of Gram-negative bacteria but not in Gram-positive bacteria?

• A. Capsule
• B. Outer membrane
• C. Teichoic acids
• D. Thick peptidoglycan layer

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the basic differences between Gram-positive and Gram-negative bacterial cell walls. Gram-positive bacteria have a thick peptidoglycan layer, while Gram-negative bacteria have a thinner peptidoglycan layer but possess an additional outer membrane.
2. Step 2: Identify the structures listed in the problem and recall which are characteristic of each bacterial type. For example, teichoic acids are typically found in Gram-positive bacteria and contribute to the thick peptidoglycan layer.
3. Step 3: Recognize that the capsule is an external structure that can be present in both Gram-positive and Gram-negative bacteria, so it is not unique to either group.
4. Step 4: Focus on the outer membrane, which is a distinctive feature of Gram-negative bacteria. This outer membrane contains lipopolysaccharides and is absent in Gram-positive bacteria.
5. Step 5: Conclude that the structure found in the cell wall of Gram-negative bacteria but not in Gram-positive bacteria is the outer membrane.