Bacillus thuringiensis (Bt) strains have been used for designing novel

Options

A. bioinsecticidal plants
B. bio-mineralization process
C. biofertilizers
D. bio-metallurgical techniques

Answer

### Step-by-Step Solution:

1. **Understanding Bacillus thuringiensis (Bt)**:
- Bacillus thuringiensis is a bacterium known for producing a specific type of endotoxin that is toxic to certain insects.

2. **Production of Endotoxin**:
- This bacterium produces a proteinaceous endotoxin, which is primarily in the form of crystal proteins.

3. **Cry Gene**:
- The gene responsible for producing these crystal proteins is known as the cry gene. This gene is crucial for the bacterium's insecticidal properties.

4. **Activation of Crystal Proteins**:
- The crystal proteins remain inactive while inside the bacterium. However, when ingested by an insect, the alkaline pH of the insect's gut activates these proteins.

5. **Mechanism of Action**:
- Once activated, the crystal proteins create pores in the gut cells of the insect. This leads to cell lysis (bursting of cells) and ultimately results in the death of the insect.

6. **Use in Agriculture**:
- Due to their ability to kill pests, Bt strains are categorized as bio-insecticides. They are used in agriculture to protect crops from insect damage.

7. **Genetic Engineering of Plants**:
- The cry gene from Bacillus thuringiensis can be incorporated into plants, making them resistant to specific pests. This results in the development of bio-insecticidal plants.

8. **Conclusion**:
- The question asks about the application of Bacillus thuringiensis strains, and the correct answer is that they are used for designing novel bio-insecticidal plants.

### Final Answer:
- **Bacillus thuringiensis (Bt) strains have been used for designing novel bio-insecticidal plants.**