|Bacillus thuringiensis (endotoxin)|
Bacillus thuringiensis is perhaps best known for its application in controlling insects through the use of plant transformation biotechnology. Plants that are genetically transformed with the gene for a lethal BT protein have been developed for a number of crops such as cotton, corn, and potatoes.
The strategy employs the use of the BT endotoxin, which is made by the bacterium Bacillus thuringiensis. These bacteria are pathogenic for a number of insect pests and their lethal effect is mediated by a protein toxin they produce. Through recombinant DNA methods, the toxin gene can be introduced directly into the genome of the plant where it is expressed and provides protection against insect pests of the plant. 
This insect management strategy has been a source of concern for entomologists, as the pollen of transgenic crops can drift onto neighboring plants and kill beneficial or non-pestilence varieties such as the monarch butterfly. These concerns appear to have been answered by research from the U.S. Department of Agriculture supporting the claim that no risk to the monarch exists from the use of BT crops.