Question

How has the bacterium Bacillus thuringiensis helped us in
controlling caterpillars of insect pests?

Answer 1

Endotoxin

Bacillus thuringiensis produces an insecticidal protein (endotoxin) that kills the caterpillar.

Mode of action

• Bt toxin is present in inactive form (protoxins) in bacteria. The endotoxin, when consumed by the caterpillar, gets activated at an alkaline pH in the gut of the insects due to solubilisation of the crystal.
• The active Bt toxin then causes the perforation in the midgut epithelium of the insects.
• This results in cell swelling followed by lysis eventually leading to the death of the insect.

Nowadays, genetically modified plants are being produced by the incorporation of the desired foreign gene into the plant genome. Bt cotton is one such example. It has a cry gene (derived from the soil-dwelling bacterium, Bacillus thuringiensis) incorporated into its genome which results in the production of Bt toxin.