Which of the following microorganisms lacks cell wall ?
Show Hint
- Azotobacter
- Rickettsia
- Mycoplasma
- Clostridium
The Correct Option is C
Solution and Explanation
Almost all prokaryotes possess a rigid, external cell wall that provides structural shape, protection, and osmotic stability.
However, a few specialized bacterial groups have evolved to survive naturally without a cell wall.
Step 2: Detailed Explanation:
Let us analyze the cellular structures of the options:
1. Mycoplasma is a genus of small, evolutionary degenerate bacteria that naturally lack a cell wall.
Because they lack peptidoglycan, they are pleomorphic (capable of changing shape) and cannot be stained by the Gram stain method.
Additionally, they are naturally resistant to beta-lactam antibiotics (like penicillin and ampicillin) that target cell wall synthesis.
2. Azotobacter is a genus of free-living, aerobic nitrogen-fixing bacteria with a robust, standard Gram-negative cell wall.
3. Rickettsia is a genus of obligate intracellular parasitic bacteria that possess a typical Gram-negative cell wall structure.
4. Clostridium is a genus of anaerobic, endospore-forming bacteria with a thick, standard Gram-positive cell wall.
Therefore, only Mycoplasma lacks a cell wall.
Step 3: Final Answer:
The microorganism that lacks a cell wall is Mycoplasma, corresponding to option (C).
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