Explanation

Bacillus thuringiensis is a Gram positive, soil dwelling bacterium, also occurs naturally in the gut of caterpillars of various types of moths and butterflies. During sporulation, B. thuringiensis forms crystals of proteinaceous insecticidal $\delta - endotoxins$ (cry toxins), which are encoded by cry genes. It was determined that the cry genes are harbored in the plasmids of B. thuringiensis strains. Cry toxins have specific activities against species of the order-Lepidoptera (moths and butterflies), Diptera (flies and mosquitoes) and Coleoptera (beetles). Thus, B. thuringiensis serves as an important reservoir of cry toxins and cry genes for the production of biological insecticides and insect resistant genetically modified crops.