The trigger for activation of toxin of Bacillus thuringiensis is

Options

A. acidic pH of stomach
B. high temperature
C. alkaline pH of gut
D. mechanical action in the insect gut

Answer

To solve the question regarding the trigger for the activation of the toxin of Bacillus thuringiensis, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Bacillus thuringiensis (Bt)**:
- Bacillus thuringiensis is a bacterium that produces a protein toxin, known as Bt toxin, which is harmful to certain insects. This bacterium is widely used in agriculture, particularly in genetically modified crops like Bt cotton, to provide pest resistance.

2. **Inactive State of Bt Toxin**:
- The Bt toxin is produced in an inactive form within the bacterium. This means that it does not pose a threat to the bacterium itself or to other organisms until it is activated.

3. **Ingestion by Insects**:
- When an insect consumes the plant material containing the Bt toxin (e.g., Bt cotton), the toxin is ingested along with the food.

4. **Conditions in the Insect Gut**:
- The environment within the insect gut is crucial for the activation of the Bt toxin. The gut has a specific pH level that can vary depending on the type of insect.

5. **Activation Trigger**:
- The key factor that activates the Bt toxin is the **alkaline pH** present in the gut of the insect. This alkaline environment triggers a conformational change in the inactive Bt toxin, converting it into its active form.

6. **Mechanism of Action**:
- Once activated, the Bt toxin binds to specific receptors in the gut cells of the insect, leading to cell lysis and ultimately causing the death of the insect. This mechanism helps protect the plant from pest damage.

7. **Conclusion**:
- Therefore, the correct answer to the question regarding the trigger for the activation of the toxin of Bacillus thuringiensis is **the alkaline pH of the gut**.

### Final Answer:
The trigger for activation of the toxin of Bacillus thuringiensis is the **alkaline pH of the gut**.