Ashbya gossypi is

Options

A. Fungus producing riboflavin
B. Fungus forming `B_(12)`
C. Actinomycetes excreting vitamin A
D. Baterium forming antibodies

Answer

**Step-by-Step Solution:**

1. **Identify the Organism**: The organism in question is Ashbya gossypii, which is also known as Eremothecium gossypii.

2. **Classification**: Ashbya gossypii is classified as a fungus. Specifically, it belongs to the kingdom Fungi and the phylum Ascomycota.

3. **Characteristics**: It is a filamentous fungus that is known for overproducing riboflavin (vitamin B2). This distinguishes it from other fungi that may produce different vitamins.

4. **Relation to Other Organisms**: Ashbya gossypii is closely related to unicellular yeasts, such as Saccharomyces cerevisiae, but it grows in a filamentous form.

5. **Historical Context**: The fungus was originally isolated from cotton as a pathogen that causes a disease known as stigma mitosis, which affects the development of hair cells in cotton plants. This discovery was made by Ashby and Noble in 1926.

6. **Evaluate Options**:
- **Option 1**: "Fungus producing riboflavin" - This is correct.
- **Option 2**: "Fungus forming B12" - This is incorrect; it produces riboflavin (B2), not B12.
- **Option 3**: "Actinomycetes excreting vitamin A" - This is incorrect; Ashbya gossypii is not an actinomycete and does not excrete vitamin A.
- **Option 4**: "Bacterium forming antibodies" - This is also incorrect; Ashbya gossypii is a fungus, not a bacterium.

7. **Conclusion**: The correct answer is that Ashbya gossypii is a fungus that produces riboflavin.