Crystallline protein synthesized by Bacillus thuringiensis is activated by

Options

A. Acidic conditions of bacterial food vacuole
B. Alkaline pH bacterial food vacuole
C. Acidic pH in insect fore-gut
D. Alkaline pH in insect mid-gut

Answer

To answer the question regarding the activation of crystalline protein synthesized by Bacillus thuringiensis, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding Bacillus thuringiensis (Bt)**:
- Bacillus thuringiensis is a bacterium that produces a crystalline protein, commonly referred to as Bt toxin. This bacterium is widely used in agriculture, particularly in genetically modified crops like Bt cotton.

2. **Nature of the Crystalline Protein**:
- The crystalline protein produced by Bacillus thuringiensis is initially synthesized in an inactive form. This means that it does not have any toxic effect until it is activated.

3. **Activation Conditions**:
- The activation of the crystalline protein occurs under specific pH conditions. The protein is activated when it enters the digestive system of an insect.

4. **Role of pH in Activation**:
- The crystalline protein becomes active in the alkaline environment of the insect's midgut. When the insect consumes the plant containing the Bt toxin, the alkaline pH in the midgut triggers the conversion of the inactive protein into its active form.

5. **Mechanism of Action**:
- Once activated, the Bt toxin binds to the gut cells of the insect, leading to cell lysis and ultimately causing the death of the pest. This mechanism makes Bt crops resistant to certain pests.

6. **Conclusion**:
- Therefore, the crystalline protein synthesized by Bacillus thuringiensis is activated by the alkaline pH in the insect midgut.

### Final Answer:
The crystalline protein synthesized by Bacillus thuringiensis is activated by the alkaline pH in the insect midgut.

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