ABSTRACT
Bacillus thuringiensis, a gram-positive, endospore-forming bacterium, is a well-known industrial organism due to its entomopathogenic properties. The original description of B. thuringiensis (Bt) and recognition of its potential utility as a biological insect control agent dates back to the early 1900s. Although generally a soil bacterium, the occurrence of Bt in a variety of diverse natural habitats, such as the phylloplanes, insect cadavers, grain dust and animal fur, has also been documented (Martin and Travers, 1989; Smith and Couche, 1991; Meadows et al., 1992; Kaelin et al., 1994). Currently, a large collection of Bt strains is available in various culture collection centers and in the laboratories of academia and industries. However, based on the relatedness of their flagellar antigens, most Bt strains could be classified into one of the —60 known serotypes (Schnepf et al., 1998).
