Apoorva Arora
Last Activity: 10 Years ago
The correct option is 2.
B. thuringiensis was first discovered in 1901 by Japanese biologist Ishiwata Shigetane. In 1911, B. thuringiensis was rediscovered in Germany by Ernst Berliner, who isolated it as the cause of a disease called Schlaffsucht in flour moth caterpillars. In 1976, Robert A. Zakharyan reported the presence of a plasmid in a strain of B. thuringiensis and suggested the plasmid's involvement in endospore and crystal formation. B. thuringiensis is closely related to B.cereus, a soil bacterium, and B.anthracis, the cause of anthrax: the three organisms differ mainly in their plasmids. Like other members of the genus, all three are aerobes capable of producing endospores. Upon sporulation, B. thuringiensis forms crystals of proteinaceous insecticidal δ-endotoxins (called crystal proteins or Cry proteins), which are encoded by cry genes. In most strains of B. thuringiensis, the cry genes are located on a plasmid (in other words, cry is not a chromosomal gene in most strains)