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