Bacillus thuringiensis is a bacterium seen on plants. This is known to produce a toxin. This toxin is in an inactive form when bacteria are on the plants. If any insect harms the plant this toxin enters the insect's gut and thus gets activated due to the gut alkaline pH. This bacterium contains genes called as Cry gene and these get activated and start attacking the cells of insects thus results in their death. Thus these bacteria act as biopesticides because of this feature, this gene from the bacterium is used to provide resistant to plants.