BACILLUS-THURINGIENSIS - FROM BIODIVERSITY TO BIOTECHNOLOGY

Bacillus thuringiensis is a Gram-positive bacterium, widely used in ag riculture as a biological pesticide, The biocidal activity mainly resi des in a parasporal protein inclusion body, or crystal, The inclusion is composed of one or more types of delta-endotoxins (Cry and Cyt prot eins). Cry proteins are selectively toxic to different species from se veral invertebrate phyla: arthropods (mainly insects), nematodes, flat worms and protozoa, The mode of action of. the insecticidal proteins i s still a matter of investigation; generally, the active toxin is supp osed to bind specific membrane receptors on the insect midgut brush-bo rder epithelium, leading to intestinal cell lysis and subsequent insec t death by starvation or septicemia. The toxin-encoding cry genes have been extensively studied and expressed in a large number of prokaryot ic and eukaryotic organisms, The expression of such genes in transgeni c plants has provided a powerful alternative for crop protection.