Question

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

• A. Is coded by several cry genes
• 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. All of the above

Answer 1

The correct option is D All of the above

The insecticidal protein crystals are encoded by several cry genes present on the bacterial plasmids. The protein crystals are produced as an inactive form, protoxin which does not kill the carrier bacterium. Thus, it is resistant to this toxin. Only in the alkaline conditions, found in the midgut of the target insect, protoxin becomes the active toxin. The active cry protein solubilizes and binds to the epithelial cells of the midgut. This leads to the formation of lytic pores in the epithelial cells eventually killing the insect. So, the correct answer is option D.