Bacillus thuringiensis

– Taxonomy and discovery
– Discovered in 1902 by Ishiwatari Shigetane in silkworms
– Later isolated by Ernst Berliner in 1911 from flour moth caterpillars
– Robert A. Zakharyan found a plasmid in a strain in 1976
– Closely related to B. cereus and B. anthracis
– Belongs to the Bacillus cereus group

– Species group placement
– Part of the Bacillus cereus group
– Includes species like B. cereus, B. anthracis, and B. thuringiensis
– More closely related to B. cereus
– Placed in a group of closely related species
– Capable of producing endospores

– Subspecies
– Several dozen recognized subspecies
– Commonly used subspecies for insecticides
– Some subspecies are clonal
– Notable subspecies include kurstaki, israelensis, and aizawai

– Genetics
– Some strains carry genes producing enterotoxins
– Known for proteins encoded by cry genes
– These genes are typically located on a plasmid
– Loss of plasmids makes it indistinguishable from B. cereus
– Plasmid exchange observed naturally

– Insecticidal properties
– Bt strains produce delta endotoxins during sporulation
– Cry proteins bind to receptors on targeted pests’ gut membranes
– Used in insecticides and genetically modified crops
– Subspecies israelensis commonly controls mosquitoes and fungus gnats
– Non-targeted organisms lack receptors and are unaffected