Question

What causes the inactive form of Bt toxin i.e. protoxin to get converted into its active form in the body of an insect?

• A. Temperature of the gut
• B. Enzymes present in the saliva
• C. Alkaline pH of the gut
• D. There is no specific reason

Answer 1

Answer: (C)

Alkaline pH of the gut

Soil bacterium Bacillus thruingiensis (Bt) produces proteins that kill certain insects like lepidopterans (tobacco budworm, armyworm), coleopterans (beetles) and dipterans (flies, mosquitoes).Bacillus thuringinesis forms some intracellular protein crystals. These crystals contain a toxic insecticidal protein. The Bt toxin protein exists as an inactive toxin and is coverted into an active form due to the alkaline pH of the alimentary canal that solubilities the crystals. The activated toxin binds to the surface of midgut epithelial cells and creates pores which cause cell swelling and lysis and finally cause death of the insect.

So, the correct answer is 'Alkaline pH of the gut'.