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Question
Crystals of Bt toxin produced by some bacteria do not kill the bacteria themselves because −
Options
bacteria are resistant to the toxin
toxin is immature
toxin is inactive
bacteria encloses toxin in a special sac.
Solution
Toxin is inactive
Explanation:
Bacillus thuringiensis produces protein crystals during a particular phase of its growth. These crystals have a deadly insecticidal protein. The Bt toxin protein exists as inactive protoxins; however, when an insect consumes the inactive toxin, it is transformed into an active form of toxin due to the alkaline pH of the insect stomach, which solubilises the crystals. The active toxin adheres to the surface of midgut epithelial cells, causing cell swelling and lysis, eventually leading to the insect's death, although it does not harm Bacillus.
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