Bacillus thuringiensis (Bt) is a gram-positive bacterium. It is a diverse population. According to the difference of its flagella antigen, the isolated Bt can be divided into 71 serotypes and 83 subspecies. The characteristics of different strains can vary greatly.
Bt can produce a variety of intracellular or extracellular bioactive components, such as proteins, nucleosides, amino polyols, etc. Bt mainly has insecticidal activity against lepidoptera, diptera and coleoptera, in addition to more than 600 harmful species in arthropods, platyphyla, nematoda and protozoa, and some strains have insecticidal activity against cancer cells. It also produces disease-resistant proto-bacterial active substances. However, in more than half of all Bt subspecies, no activity has been found.
The complete life cycle of Bacillus thuringiensis includes alternating formation of vegetative cells and spore. After activating, germinating and exiting the dormant spore, the volume of the cell increases rapidly, forming the vegetative cells, and then propagating in the way of binary division. When the cell has divided for the last time, spore formation begins again rapidly.