Question

Bacillus thuringiensis forms protein crystals which contain insecticidal protein. This protein

• A. Is activated by acid pH of the foregut of the insect pest.
• B. Does not kill the carrier bacterium which is itself resistant to this toxin.
• C. Binds with epithelial cells of midgut of the insect pest ultimately killing it.
• D. None of the above

Answer 1

The correct option is C Binds with epithelial cells of midgut of the insect pest ultimately killing it.

The cry proteins exist as inactive protoxins and get converted into active toxin when ingested by the insect, as the alkaline pH of gut solubilizes the crystals. The activated toxin binds to the surface of epithelial cells of the midgut and blocks the gut which leads to the lysis of cells and the death of the insect (larva).

Thus, the correct option is (C).