Essay --

Introduction Bacillus thuringiensis (Bt) has become the foremost biopesticide since the beginning of the 1970s, due to the lethality of the toxin to insects. It has attracted industry to use it worldwide as an efficient weapon against agri-cultural pest. formerly, B. thuringiensis was considered an entomopathogen. Within the last four decades the complexity and diversity of B. thuringiensis as an insecticidal microbe have been elucidate. The first report on the crystalline parasporal body in the bacterium that might be related with the insecticidal activity appeared by 1953 (Hannay, 1953). Angus (1954) demonstrated that this crystal contains an alkaline- soluble toxin for insects. B. thuringiensis produces a f3-exotoxin well-known also as the fly-toxin, thermostable toxin, or thuringiensin, but this toxin was not permitted for use in agriculture because its toxicity was not limited to insect pests (Sebesta et al., 1981). The 8-endotoxin shows potential characteristics of an insect-specific bioinsecticide. By the end of the 1950s, the toxicity of the spore–crystal complex was classif...