Final answer:
Bacillus thuringiensis produces protein crystals known as Bt toxin, which are toxic to insects and can be inserted into plants using recombinant DNA technology to provide a natural insecticidal property.
Step-by-step explanation:
The bacterium Bacillus thuringiensis produces protein crystals during sporulation that are toxic to insects. These protein crystals are known as Bt toxin, and they need to be ingested by insects to be activated. Once ingested, affected insects stop feeding and eventually die after the toxin activates in their intestines. Modern biotechnology has enabled the encoding of plants with their own crystal Bt toxin gene to act against insects. This is achieved by cloning the crystal toxin genes from Bacillus thuringiensis and incorporating them into plants using recombinant DNA technology. Organic farmers approve of Bt toxin as a natural insecticide because it is safe for the environment and non-toxic to humans and other mammals.