To decrease reliance on insecticide sprays, scientists have genetically engineered plants to make insecticidal proteins encoded through genes from the common bacterium Bacillus thuringiensis http://biochemistry.euroscicon.com(Bt). Currently, due to their importance, more than 70 kinds of Cry genes are described (cry1 up to cry70).Bacillus thuringiensis (Bt) is a soil bacterium that forms spores during the stationary phase of its growth cycle. The spores contain crystals, predominantly comprising one or more Cry and/or Cyt proteins (also known as δâ€endotoxins) that have potent and specific insecticidal activity. Different strains of Bt produce different types of toxin, each of which affects a narrow taxonomic group of insects. Bacillus thuringiensis (or Bt) is a Gram-positive, soil-dwelling bacterium, commonly used as a biological pesticide. B. thuringiensis also occurs naturally in the gut of caterpillars of various types of moths and butterflies, as well on leaf surfaces, aquatic environments, animal feces, insect-rich environments, and flour mills and grain-storage facilities.