Mark the odd one w.r.t. cell wall.

Options

A. Halophiles
B. Methanogens
C. Thermoacidophiles
D. Cyanobacteria

Answer

### Step-by-Step Solution:

1. **Identify the Groups**: The question asks to identify the odd one out with respect to the cell wall. The options provided are halophiles, thermophiles, methanogens, thermoacidophiles, and cyanobacteria.

2. **Classify the Options**:
- Halophiles, thermophiles, methanogens, and thermoacidophiles are all types of Archaebacteria.
- Cyanobacteria, on the other hand, belong to the group of Eubacteria.

3. **Understand Cell Wall Composition**:
- Archaebacteria (including halophiles, thermophiles, methanogens, and thermoacidophiles) have cell walls made of pseudopeptidoglycan, which is different from the typical peptidoglycan found in many bacteria.
- Cyanobacteria have a cell wall that contains peptidoglycan, along with polysaccharides and lipopolysaccharides.

4. **Determine the Odd One Out**: Since cyanobacteria are classified as Eubacteria and have a different cell wall structure (containing peptidoglycan) compared to the Archaebacteria (which have pseudopeptidoglycan), cyanobacteria is the odd one out.

5. **Conclusion**: The answer to the question is **Cyanobacteria**.