Question

Bt endotoxin that exists as inactive protoxin is converted into active toxin once bollworm ingests it due to

• A. activity of protease enzyme in gut
• B. high metabolic activity in gut
• C. acidic pH in gut
• D. alkaline pH in gut

Answer 1

The correct option is D alkaline pH in gut

Bt toxin is the most popular bio-pesticide. It is a crystal protein having insecticidal properties produced by the bacterium, Bacillus thuringiensis.

Bacillus thuringiensis forms crystalline proteins that are insecticidal (cry proteins). The endotoxin that accumulates in bacteria is in an inactive form (protoxin). It gets activated at an alkaline pH in the gut of the insects due to the solubilisation of the crystal proteins.

This active toxin generates pores in the epithelium of the midgut of the insects which results in the swelling of cells followed by lysis. This consequently results in the death of the insect.

Hence the correct option is
a. alkaline pH in gut