Question

Crystals of Bt toxin produced by some bacteria do not kill the bacteria themselves because ______.

Options

• bacteria are resistant to the toxin

• toxin is immature

• toxin is inactive

• bacteria encloses toxin in a special sac

Answer 1

Crystals of Bt toxin produced by some bacteria do not kill the bacteria themselves because toxin is inactive.

Explanation:

Bacillus thuringiensis forms protein crystals during a particular phase of its growth. These crystals contain a toxic insecticidal protein. Actually, the Bt toxin protein exists as inactive protoxins, but once an insect ingests the inactive toxin, it is converted into an active form by the alkaline pH of the insect gut, which solubilises the crystals. The activated toxin binds to the surface of midgut epithelial cells, creating pores that cause cell swelling and lysis, eventually leading to the insect’s death, but it does not harm Bacillus itself.