Question

What is the mechanism by which Bacillus thuringiensis (Bt) kills insect larvae?

Options

• Bt spores germinate inside the larva and consume all nutrients

• Bt toxin crystals are released in the larva's gut after ingestion, killing the larvae

• The larvae are suffocated by dried spores coating their bodies

• The toxin prevents larvae from reproducing sexually

Answer 1

Bacillus thuringiensis produces crystals of a protein called Bt toxin in its endospore form. When insect larvae ingest these dried spores mixed with water, the toxin is released in their gut, leading to their death. This mechanism makes Bt effective against butterfly caterpillars and other insect pests.