NEET2026BiologyChapterActual
Which of the following best explains why the insecticidal protein produced by Bacillus thuringiensis is harmless to the bacterium but lethal to the target insect?
Options
- AThe bacterium lacks the specific target organs, whereas the toxin directly attacks the insect's central nervou
- BThe toxin is synthesized as an inactive protoxin that requires the alkaline pH of the insect gut to become act
- CThe bacterial cytoplasm contains specific enzymes that continuously degrade the active toxin before it can cau
- DThe toxin is activated by the highly acidic environment of the insect's stomach, which is absent in the bacter
Correct answer
B. The toxin is synthesized as an inactive protoxin that requires the alkaline pH of the insect gut to become act
Step-by-step solution
The insecticidal protein produced by Bacillus thuringiensis is synthesized in an inactive form known as a protoxin. When a target insect ingests the inactive protoxin, it enters the insect's gut. The alkaline pH of the insect's midgut solubilizes the protein crystals and converts the inactive protoxin into an active toxin. The active toxin then binds to the surface of midgut epithelial cells, creating pores that cause cell swelling and lysis, eventually leading to the death of the insect. Since the bacterium lacks