Identification and characterization of IS-like elements in Mycobacterium gordonae

Abstract

A new insertion sequence, IS 1512, from Mycobacterium gordonae was cloned and sequenced. This element is present in up to 10 copies which provides a high diversity for restriction fragment length polymorphism analysis. We have also identified truncated IS 1512-like elements, including a truncated IS 1512 and another truncated insertion sequence which displays homology with IS 1512 and was designated IS 1511. Sequences homologous to the previously described transposon Tn 554 are inserted into these truncated insertion sequences. Insertion loci of IS 1511/IS 1512 are shown to be highly related to those described for IS 256-like elements in other species. Alignment of the putative transposases from Rhodococcus and Mycobacterium suggests these insertion sequences may form a distinct closely homologous subclass within the IS 256 family. Analysis comparing phylogenetic divergence of these elements with that of 16S rRNA and superoxide dismutase genes suggests horizontal transfer of a IS 1511/IS 1512 precursor into M. gordonae, and the occurrence of horizontal transfer between Mycobacteriaceae and Rhodococcaceae.