Branched chain lipids occur in the cell membranes of
(a) Methanobacterium
(b) Mycoplasma
(c) Actinomycetes
(d) Streptomyces

Options

A. Methanobacterium
B. Mycoplasma
C. Actinomycetes
D. Streptomyces

Answer

To determine which organism has branched chain lipids in its cell membrane, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Branched Chain Lipids**:
- Branched chain lipids are typically found in organisms that can survive in extreme environmental conditions. These lipids are characteristic of certain types of bacteria known as archaebacteria.

2. **Identify the Types of Organisms Listed**:
- (a) Methanobacterium
- (b) Mycoplasma
- (c) Actinomycetes
- (d) Streptomyces

3. **Analyze Each Option**:
- **Methanobacterium**: This is an archaebacterium known to thrive in extreme conditions, such as anaerobic environments, and is capable of producing methane. It is known to have branched chain lipids in its cell membrane.
- **Mycoplasma**: These are bacteria that lack a cell wall and typically do not have branched chain lipids.
- **Actinomycetes**: These are a group of bacteria that are more similar to typical bacteria and do not possess branched chain lipids.
- **Streptomyces**: Another type of bacteria that does not have branched chain lipids in its membrane.

4. **Conclusion**:
- Since Methanobacterium is the only organism listed that is known to have branched chain lipids in its cell membrane, the correct answer is **(a) Methanobacterium**.

### Final Answer:
(a) Methanobacterium