Anoxygenic photosynthesis is characteristic of

Options

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

Answer

### Step-by-Step Solution:

1. **Understanding Anoxygenic Photosynthesis**:
- Anoxygenic photosynthesis is a type of photosynthesis that does not produce oxygen as a byproduct. This process is primarily found in certain types of bacteria.

2. **Identifying Key Characteristics**:
- In anoxygenic photosynthesis, water is not used as a source of electrons (reducing power). Instead, these organisms obtain hydrogen from other sources, which can be either organic or inorganic compounds.

3. **Analyzing the Options**:
- **Option A: Vulva** - This is not a known organism related to photosynthesis.
- **Option B: Rhodospirillum** - This is a genus of bacteria known for its ability to perform anoxygenic photosynthesis.
- **Option C: Spirogyra** - This is a green algae that performs oxygenic photosynthesis, using water as a source of electrons.
- **Option D: Chlamydomonas** - This is a unicellular green algae that also performs oxygenic photosynthesis.

4. **Conclusion**:
- Based on the characteristics of anoxygenic photosynthesis and the analysis of the options, the correct answer is **Option B: Rhodospirillum**. This organism is specifically known for its anoxygenic photosynthetic capabilities.