Which of the following lacks peptidoglycan in their cell walls :–

Options

A. Halophile bacteria
B. Methanogen bacteria
C. Thermoacidophilic bacteria
D. All the above

Answer

To solve the question "Which of the following lacks peptidoglycan in their cell walls?", we need to analyze each option provided. Peptidoglycan is a polymer that forms a protective layer in the cell walls of many bacteria, but not all.

### Step-by-Step Solution:

1. **Identify the Options**: The question presents four options:
- Halophile Bacteria
- Methanogen Bacteria
- Thermoacidophilic Bacteria
- All of the above

2. **Analyze Halophile Bacteria**:
- Halophiles are microorganisms that thrive in high-salinity environments.
- They have unique adaptations that allow them to survive in these conditions, and their cell walls do not contain peptidoglycan.

3. **Analyze Methanogen Bacteria**:
- Methanogens are a group of archaea that produce methane as a by-product of their metabolism.
- They are known to lack peptidoglycan in their cell walls, as they are part of the Archaea domain, which typically does not have this component.

4. **Analyze Thermoacidophilic Bacteria**:
- Thermoacidophiles are also a type of archaea that thrive in hot and acidic environments.
- Similar to methanogens, they do not possess peptidoglycan in their cell walls.

5. **Evaluate the Final Option**:
- The last option states "All of the above". Since all the previous options (Halophile, Methanogen, and Thermoacidophilic bacteria) lack peptidoglycan in their cell walls, this option is correct.

6. **Conclusion**:
- The correct answer is "All of the above" as all the mentioned types of bacteria do not have peptidoglycan in their cell walls.

### Final Answer:
**The correct option is: All of the above.**