Which of the following features distinguishes the cell wall of Gram-positive bacteria from that of Gram-negative bacteria?

• A. Presence of periplasmic space between two membranes
• B. A thin peptidoglycan layer and presence of an outer membrane
• C. A thick peptidoglycan layer and absence of an outer membrane
• D. Presence of lipopolysaccharide in the cell wall

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the basic structure of bacterial cell walls. Gram-positive and Gram-negative bacteria differ primarily in their cell wall composition and architecture.
2. Step 2: Recall that Gram-positive bacteria have a thick peptidoglycan layer, which provides rigidity and retains the crystal violet stain during Gram staining.
3. Step 3: Note that Gram-negative bacteria have a thin peptidoglycan layer located between two membranes: the inner cytoplasmic membrane and an outer membrane, which contains lipopolysaccharides (LPS).
4. Step 4: Recognize that the periplasmic space is the area between the inner and outer membranes in Gram-negative bacteria, but this space is minimal or absent in Gram-positive bacteria due to the lack of an outer membrane.
5. Step 5: Conclude that the distinguishing feature of Gram-positive bacteria is the presence of a thick peptidoglycan layer and the absence of an outer membrane, unlike Gram-negative bacteria which have a thin peptidoglycan layer and an outer membrane containing LPS.