DISTRIBUTION OF THE INSERTION ELEMENT IS240 AMONG BACILLUS-THURINGIENSIS STRAINS

The presence of IS240 was investigated in 69 Bacillus thuringiensis (B t) strains including strains from serotype H1 to H45 and additional st rains with known Dipteran larvae toxicity. Restriction digests of tota l DNA and PCR products obtained with a single 16-bases primer correspo nding to the IS240 inverted repeated sequence were hybridized with the IS240A element. The results indicate that 67% of the Br strains teste d, including all known mosquitocidal strains, possess at least one IS2 40-related element. PCR experiments indicate that IS240 represents a f amily of insertion sequences with several variants.