Tris-dependent site-specific cleavage of Streptomyces lividans DNA

The copy number and location of the insertion sequence IS200, a mobile DNA element, was established across a collection of Salmonella berta. All strains contained one common site, assumed to be present in the evolutionary ancestor of this serovar. With one exception, all strains, including recent outbreak isolates from the UK and sporadic isolates of world-wide distribution, were representatives of a single genotypic clone which carried three common IS200 insertion sites. This clone has acquired diverse combinations of plasmids, reflecting its actual or recent distribution and host. A single isolate, belonging to a second, minor genotypic clone was characterised by two IS200 insertion sites.