IDENTIFICATION AND CHARACTERIZATION OF IS-LIKE ELEMENTS IN MYCOBACTERIUM-GORDONAE

A new insertion sequence, IS1512, from Mycobacterium gordonae was clon ed and sequenced. This element is present in up to 10 copies which pro vides a high diversity for restriction fragment length polymorphism an alysis. We have also identified truncated IS1512-like elements, includ ing a truncated IS1512 and another truncated insertion sequence which displays homology with IS1512 and was designated IS1511. Sequences hom ologous to the previously described transposon Tn554 are inserted into these truncated insertion sequences. Insertion loci of IS1511/IS1512 are shown to be highly related to those described for IS256-like eleme nts in other species. Alignment of the putative transposases from Rhod ococcus and Mycobacterium suggests these insertion sequences may form a distinct closely homologous subclass within the IS256 family. Analys is comparing phylogenetic divergence of these elements with that of 16 S rRNA and superoxide dismutase genes suggests horizontal transfer of a IS1511/IS1512 precursor into M. gordonae, and the occurrence of hori zontal transfer between Mycobacteriaceae and Rhodococcaceae.