Bt

Bt, short for Bacillus thuringiensis, is a Gram-positive bacterium found in soils worldwide. It produces crystalline protein inclusions during sporulation, which serve as insecticidal toxins. Different strains generate various Cry and Cyt toxins that target specific groups of insects, particularly Lepidoptera (caterpillars), Diptera (fly larvae), and Coleoptera (beetles).

The insecticidal action involves ingestion of the crystal proteins by larvae, solubilization and activation of the toxins in the gut, binding to receptors on midgut cells, and pore formation that disrupts gut integrity, leading to death. This mechanism provides species- or group-specific control with relatively low risk to many non-target organisms, including humans.

Applications include formulated microbial pesticides used in conventional agriculture, forestry, and vector control, as well as Bt crops engineered to express Cry proteins. Bt crops such as corn and cotton have been adopted in many countries to reduce reliance on chemical insecticides. In addition to food production, Bt toxins are used in public health programs to control mosquito populations, notably by Bt israelensis (Bti).

Safety and environmental considerations emphasize generally favorable risk profiles, though concerns about non-target effects on beneficial insects and the development of resistance in target pests exist. Resistance management strategies include rotating Bt toxins with different modes of action and deploying refuges to maintain susceptible pest populations.

The name Bacillus thuringiensis reflects its discovery in the early 20th century and its designation from the Thuringia region in Germany, where related work helped formalize its taxonomy and use.