A rod-shaped bacterium (Bt for short) from the order Bacillaceae. The name was derived from the fact that it was isolated from a flour moth in 1911, which came from a mill in Thuringia. It is a soil bacterium that lives in company with plant roots and contains a protein crystal that is toxic to certain insects. The toxins protect the roots from damage by insects. Genes transferred to crops cause plants to produce Bt toxins on their own. These have a lethal effect on the larvae of insects of the orders of beetles, butterflies and diptera (mosquitoes and flies). After being eaten by the larvae, it is released in their intestines and unfolds its lethal effect. In plants and vertebrates such as humans, however, the bacterium is ineffective and is completely biodegradable.