Anoxygenic photosynthesis is characteristic of

Options

A. Rhodospirillum
B. Spirogyra
C. Chlamydomonas
D. Ulva

Answer

To solve the question "Anoxygenic photosynthesis is characteristic of?", we can follow these steps:

### Step 1: Understand Anoxygenic Photosynthesis
Anoxygenic photosynthesis is a type of photosynthesis that does not produce oxygen as a byproduct. This process is different from oxygenic photosynthesis, where water is used as a reducing agent, and oxygen is released.

### Step 2: Identify the Characteristics
In anoxygenic photosynthesis:
- Oxygen is not evolved.
- Water is not used as a reducing agent.
- Instead, other substances like hydrogen sulfide (H2S) may be used.

### Step 3: Analyze the Options
We have four options to consider:
1. Rhodospirillum
2. Spirogyra
3. Chlamydomonas
4. Alba

### Step 4: Determine Which Organisms Perform Anoxygenic Photosynthesis
- **Rhodospirillum**: This is a genus of purple non-sulfur bacteria that perform anoxygenic photosynthesis.
- **Spirogyra**: This is a green algae that performs oxygenic photosynthesis.
- **Chlamydomonas**: This is also a green algae that performs oxygenic photosynthesis.
- **Alba**: This term is too vague without context but does not refer to a known group of anoxygenic photosynthetic organisms.

### Step 5: Conclusion
Based on the analysis, the correct answer is **Rhodospirillum**, as it is the only organism listed that is known to perform anoxygenic photosynthesis.

### Final Answer
Anoxygenic photosynthesis is characteristic of **Rhodospirillum**.

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