Identification of a cryptic gene associated with an insertion sequence not previously identified in Bacillus thuringiensis.

After screening several Bt strains with a cryII toxin probe, clones from two strains were found to contain a cryptic cryIIB gene associated with an insertion sequence element belonging to the IS2/IS3 family. The lack of expression of this gene appears to result from mutation of the upstream orf2 gene which has been shown to be necessary for cryII expression.