Question

Certain specific bacterial spores are mixed in water and sprayed over Brassica crop to control butterfly caterpillars.

Name this bacterium and its mode of action on the butterfly caterpillars.

Answer 1

Bacillus thuringiensis

Mode of action: 

Certain Bacillus thuringiensis strains produce proteins that are lethal to several insects, including coleopterans (beetles), lepidopterans (tobacco bud worm, armyworm), and dipterans (flies, mosquitoes). During one stage of its growth, B. thuringiensis produces protein crystals. The Bt protein, a toxic insecticide, is present in these crystals. The B toxin protein is an inactive protoxin in bacteria, but when consumed by an insect, the inactive toxin is changed into an active form of the toxin by the gut's alkaline pH, which destroys the crystals. The middle gut epithelial cells' surface is where the activated toxin binds, opening gaps that eventually kill the insect by causing cell swelling and lysis.