Lipopolysaccharide (LPS), a major component of the outer membrane, is characteristic of which group of bacteria?

A Gram-positive bacteria

B Gram-negative bacteria

C Acid-fast bacteria

D Mycoplasma species

Solution

Correct Answer: Option B

- Lipopolysaccharide (LPS) is an essential component of the outer membrane found exclusively in Gram-negative bacteria.
- It contributes to the structural integrity of the outer membrane and acts as an endotoxin, triggering strong immune responses in the host.
- In contrast, Gram-positive bacteria lack an outer membrane and therefore do not contain LPS.
- Acid-fast bacteria have a unique waxy cell wall rich in mycolic acids, and Mycoplasma species lack a cell wall entirely.
- This makes LPS a hallmark feature distinguishing Gram-negative bacteria.

Reference: Jawetz, Melnick & Adelberg's Medical Microbiology, 28th Edition, Chapter 3: Structure of Bacteria

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