Bacillus thuringiensis (Bt)
Soil bacterium used for biological pest control - produces a crystalline protein toxic to certain types of insects.
Bt toxin is produced by Bacillus thuringiensis in an inactive form (protoxin), which is transformed to its active form (delta-endotoxin) in the guts of certain insects. The active toxin binds to receptors in the gut, killing the insect.
Insect pests have long been fought with Bacillus thuringiensis products. Based on the premise that – as opposed to many chemical insecticides – they are harmless to humans, they are used in organic farming.
By means of genetic engineering, the genes for the active agent (Bt toxin) can be transferred from Bt bacteria to plants. There they produce the toxic agent inside the plant cells. In this way, biotechnology has been used to confer insect resistance to a number of economically important crops. Bt maize and Bt cotton are widely grown in several countries.