Obligate intracellular parasites other than virus are

Options

A. Rickettsiae
B. Azotobacter
C. Azospirillum
D. Mycoplasma

Answer

### Step-by-Step Solution:

1. **Understanding Obligate Intracellular Parasites**:
- Obligate intracellular parasites are organisms that cannot reproduce outside of a host cell. They rely on the host's cellular machinery for reproduction and survival.

2. **Identifying the Options**:
- The question lists several organisms: Rickettsia, Azotobacter, Azospirillum, and Mycoplasma. We need to determine which of these are obligate intracellular parasites.

3. **Analyzing Each Option**:
- **Rickettsia**: This is an obligate intracellular parasite. It is a type of bacteria that requires a host cell to reproduce and can cause diseases in humans.
- **Azotobacter**: This is a free-living nitrogen-fixing bacterium that does not require a host to survive. Therefore, it is not an obligate intracellular parasite.
- **Azospirillum**: Similar to Azotobacter, this is also a nitrogen-fixing bacterium that lives independently in the soil and does not require a host.
- **Mycoplasma**: This is a type of bacteria that lacks a cell wall. While it can cause infections, it is not classified as an obligate intracellular parasite because it can survive outside of host cells.

4. **Conclusion**:
- Based on the analysis, the only obligate intracellular parasite from the options provided is **Rickettsia**.

### Final Answer:
**Rickettsia** is the obligate intracellular parasite other than viruses.

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