Molecular genetic studies of the DNA promotor regions in Bacillus thuringiensis subsp. galleriae 69-6. II. Increased level of gene expression resulting from IS1 element integration

The 1.45 kb promoter containing HindIII fragment of Bacillus thuringiensis DNA promotes the expression of the tet gene of recombinant pPBT9 plasmid in Escherichia coli cells. Spontaneous mutants of this plasmid were isolated and analysed. They are responsible for an increase in the level of tetracycline resistance. This 3-fold increase resulted from integration of IS1 element into the bacillar promoter containing HindIII fragment, which led to formation of a mutant pPBT9::IS1 plasmid. The IS sequence integrated was defined as an IS1 element of the E. coli HB101 chromosomal DNA. The integration site of IS1 was localized.