Transposition of IS 1397 in the Family Enterobacteriaceae and First Characterization of ISKpn 1 , a New Insertion Sequence Associated with Klebsiella pneumoniae Palindromic Units

IS 1397 and ISKpn 1 are IS 3 family members which are specifically inserted into the loop of palindromic units (PUs). IS 1397 is shown to transpose into PUs with sequences close or identical to the Escherichia coli consensus, even in other enterobacteria ( Salmonella enterica serovar Typhimurium, Klebsiella pneumoniae , and Klebsiella oxytoca ). Moreover, we show that homologous intergenic regions containing PUs constitute IS 1397 transpositional hot spots, despite bacterial interspersed mosaic element structures that differ among the three species. ISKpn 1 , described here for the first time, is specific for PUs from K. pneumoniae , in which we discovered it. A sequence comparison between the two insertion sequences allowed us to define a motif possibly accounting for their specificity.