Why does Bt toxin cannot kill the bacterium that produces it, but kills the insect that ingests it?

Explanation

Bt toxin is produced by a soil bacterium called Bacillus thuringiensis. This toxin does not kill the bacterium which produces it, because in them, it is present in an inactive and crystalline förin. It becomes active and toxic only when it is consumed by insects such as lepidopterans, etc., due to che alkaline pH of the gut.