B. thuringiensis Crystals

    The crystals inside of Bt are sometimes referred to as insecticidal crystal proteins (ICP). These crystals are formed

during the sporulation (the forming of spores) of Bt strains. During the sporulation proteins form together to make the

crystals.

    These crystals are highly specific to certain insects, but they are harmless to humans and other wildlife. Today, there

are more than 150 insects known to be susceptible to Bt.

    The crystals bind to the receptors in the insect's intestine after the Bt is ingested. The reason why Bt strains are highly

specific is that insects have different receptors in their intestine. Other vertabrates and humans do not have these receptors,

therefore, we are not susceptible to the crystals.