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

**Step-by-Step Solution:**

1. **Understanding Bacillus thuringiensis**: Bacillus thuringiensis (Bt) is a soil bacterium known for its ability to produce a protein that is toxic to certain insects.

2. **Production of Protoxin**: The bacterium produces an inactive form of the toxin known as protoxin. This protoxin is not harmful until it undergoes a specific activation process.

3. **Ingestion by Insects**: The activation of the protoxin occurs when it is ingested by certain insects, particularly those belonging to the orders Lepidoptera (moths and butterflies), Diptera (flies), and Coleoptera (beetles).

4. **Role of Alkaline pH**: Once ingested, the protoxin interacts with the alkaline pH environment of the insect's gut. This alkaline condition is crucial for the activation of the protoxin.

5. **Activation to BT Toxin**: The interaction with the alkaline pH leads to the conversion of the protoxin into its active form, known as the BT toxin.

6. **Mechanism of Action**: The activated BT toxin then binds to the surface of the midgut cells of the insect, causing cell swelling and ultimately leading to the insect's death.

7. **Conclusion**: Therefore, the trigger for the activation of the toxin of Bacillus thuringiensis is the alkaline pH of the insect gut.

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

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