'Bt' toxin is

Options

A. Intracellular lipid
B. Intracellular crystalline protein
C. Extracellular crystalline protein
D. Lipid

Answer

**Step-by-Step Solution:**

1. **Identify the Source of Bt Toxin**:
- Bt toxin is produced by a specific bacterium known as Bacillus thuringiensis.

2. **Classify the Bacterium**:
- Bacillus thuringiensis is classified as a gram-negative bacterium.

3. **Nature of Bt Toxin**:
- The toxin produced by Bacillus thuringiensis is an extracellular crystalline protein.

4. **Mechanism of Action**:
- When insects ingest Bt toxin, it interacts with their gut proteins.

5. **Effect on Insects**:
- The interaction of Bt toxin with the insect gut proteins leads to the blockage of these proteins, ultimately resulting in the death of the insect.

6. **Conclusion**:
- Therefore, Bt toxin is an extracellular crystalline protein produced by the gram-negative bacterium Bacillus thuringiensis, which is lethal to certain insects upon ingestion.

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