Question

Select the correct statement regarding Bt toxins produced by bacterium Bacillus thuringiensis.

• A. Most strains of Bacillus thuringiensis produce proteins that kill certain insects such as lepidopterans, coleopterans and dipterans.
• B. Bt toxin proteins do not kill the bacteria themselves because the toxin proteins occur in an inactive form called protoxins.
• C. When an insect ingests the inactive Bt toxin, it is converted to an active form of toxin due to alkaline pH of the gut which solubilises the protein toxin crystals.
• D. All of these.

Answer 1

Answer: (D)

Bacillus thuringiensis is a kind of bacterium that can produce a toxin called Bt-toxin or cry protein that kills most insects like dipterans, coleopterans, and lepidopterans. It does not kill the bacteria themselves because the toxin occurs in an inactive form called protoxins. When an insect ingests the inactive Bt toxin, it is converted to an active form of toxin, due to which the alkaline pH of the gut, that solubilizes the protein toxin crystals.