ABSTRACT
This chapter describes some of the most interesting aspects of the most widely commercial used bioinsecticide, Bacillus thuringiensis (Bt), because it is a good model to understand the problems of replacing toxic agrochemicals with biodegradable products. The elucidation of the mechanism of action of the Bt toxins is, besides the search for novel activities, the big area of interest in the field of the Bt bioinsecticides. The δ-endotoxins, the main constituent of the crystals, have recently attracted the attention of several research groups and also of some international companies for two reasons: δ-endotoxins with novel activities have been discovered, and the arrival of molecular biology to agriculture has generated transgenic plants containing the cry genes. In the USA from 1993 to 1996, 17 transgenic plants were approved for widespread use and production, six of which were resistant to insects due to the introduction of the δ-endotoxin Bt genes.
