[Tn9 integration sites and their effect on transposon properties]

The insertion of transposable deoxyribonucleic acid sequence that specifies chloramphenicol acetyltransferase (Tn9) occurs in the preferential sites of the Escherichia coli K-12 chromosome. It is found that some strains of E. coli K-12 have different preferential sites for the Tn9 insertion, located in various regions of the chromosome. The IS1 element inserted into the galT gene of the N116 strain (insertion mutation galT 116:IS1) serves as a strongly preferential site for the Tn9 insertion in this strain. However, being transferred into the chromosome of the KS836 strain this element loses such preference. It was demonstrated that the transposons (Tn9) inserted into different chromosomal sites are distinguished by such properties as stability, different capability to transposition into genomes of bacteriophages and plasmids, and by the choice of the preferential sites of integration in the course of subsequent insertions.