Insertion sequence (IS ) is involved in the genomic plasticity of .

The genome of the fish pathogen subsp harbors a large number of insertion sequences (ISs), many of which are located on plasmids. In the present study, we analyzed the small plasmid profile of strains to identify evidences of plasmid alterations. Ten out of 78 strains analyzed displayed an unconventional plasmid profile. However the HER1104 strain was unique, having a positive PCR signal for pAsal1 plasmid despite not carrying this plasmid. Instead, HER1104 was bearing a plasmid at higher molecular weight than pAsal1. We characterized this new larger plasmid, which we called pAsal1B since it is a derivative of pAsal1 containing one more complete IS (IS) than the parental plasmid. An additional 96 bp relic of IS was also present in pAsal1B. These results propose that IS is another active mobile genetic element in subsp and provided further proof of the genomic plasticity of this bacterium.