Which of the following statements about Bacillus thuringiensis are correct?
A. One of the toxin produced by the bacteria is thurioside, which is active against different groups of insect larvae.
B. The toxin accumulates inside the bacteria during sporulation.
C. Upone ingestion by susceptible insects they are converted into active form and kill them by inhibition of ion transport in the midgut.
D. The proteins encoded by the gene Cry II Ab contrls com borer.

Options

A. B only
B. A and B
C. A, B and C
D. A, B, C and D

Answer

To determine which statements about Bacillus thuringiensis (Bt) are correct, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Evaluate Statement A**:
- The statement claims that one of the toxins produced by Bacillus thuringiensis is "thurioside," which is active against different groups of insect larvae.
- **Analysis**: The correct toxin produced by Bt is the Cry toxin, not "thurioside." Therefore, this statement is **false**.

2. **Evaluate Statement B**:
- The statement claims that the toxin accumulates inside the bacteria during sporulation.
- **Analysis**: During sporulation, the Cry proteins (toxin) do accumulate within the bacterial cells. This statement is **true**.

3. **Evaluate Statement C**:
- The statement claims that upon ingestion by susceptible insects, the toxins are converted into an active form and kill them by inhibiting ion transport in the midgut.
- **Analysis**: The Cry toxins are indeed activated in the alkaline environment of the insect gut, but they do not inhibit ion transport. Instead, they create pores in the midgut epithelial cells, leading to cell lysis and death. Therefore, this statement is **false**.

4. **Evaluate Statement D**:
- The statement claims that the proteins encoded by the gene Cry II Ab control the corn borer.
- **Analysis**: The correct gene that controls the corn borer is Cry I Ab, not Cry II Ab. Therefore, this statement is **false**.

### Conclusion:
- The only correct statement is **B**: "The toxin accumulates inside the bacteria during sporulation."
- Thus, the correct answer is option **B**.

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