Identification of two sequence elements associated with the gene encoding the 24-kDa crystalline component in Bacillus thuringiensis ssp. fukuokaensis: an example of transposable element archaeology.

A 6.5-kb fragment of plasmid DNA from Bacillus thuringiensis (Bt) ssp. fukuokaensis that encodes a 24-kDa crystalline component was analyzed to identify additional open reading frames (orfs). A novel Bt IS240-like element was found upstream of this gene and is considered to be a vestige of a once active insertion sequence due to a stop codon that interrupts the long orf encoding the putative transposase. This element was bounded by 17-bp terminal inverted repeats that defined the length of the insertion sequence as 802 bp. Further upstream of this element two tandem overlapping and out of phase open reading frames (orfX and orfY) were identified which represent the first example of an IS150-like element in Bt containing both orfs. orfX and orfY are not bounded by terminal inverted repeats but are associated with a gene encoding a putative site-specific recombinase of a type found in Staphylococcus aureus Class II transposons but not previously in Bt.