Which of the following features is typical of Gram-positive bacteria?

A Presence of a thick peptidoglycan layer

B Outer membrane containing lipopolysaccharides

C Thin peptidoglycan layer with periplasmic space

D High lipid content in cell wall making it resistant to Gram stain

Solution

Correct Answer: Option A

- The correct answer is Presence of a thick peptidoglycan layer.

- Gram-positive bacteria are characterized by a thick, multilayered peptidoglycan cell wall that retains the crystal violet-iodine complex during Gram staining, resulting in a purple color.
- Unlike Gram-negative bacteria, they lack an outer membrane and lipopolysaccharides.
- This thick peptidoglycan layer is the key structural feature that differentiates Gram-positive bacteria in the Gram stain process.

Reference: Jawetz, Melnick & Adelberg’s Medical Microbiology, 28th Edition, Chapter 3, Page 42

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