IDENTIFICATION AND ACTIVITY OF 2 INSERTION-SEQUENCE ELEMENTS IN RHODOCOCCUS SP STRAIN IGTS8

Two putative insertion sequence (IS) elements, IS1166 and IS1295, were identified on a plasmid present in Rhodococcus sp. IGTS8. Four copies of IS1166 were present in strain IGTS8: one copy on each of two separ ate plasmids and two copies on a third plasmid or in the chromosome. O f eight rhodococci tested, only R. zopfii contained a copy of an IS116 6-like element. Two mutants of strain IGTS8 were isolated in which an additional copy of IS1166 was present, suggesting that at least one co py of this element may be able to transpose. IS1166 and IS1295 are new members of a family of IS elements which includes IS6120 from Mycobac terium smegmatis, IST2 from Thiobacillus ferrooxidans, IS256 from Stap hylococcus aureus and ISRm3 from Rhizobium meliloti. The 24-25-bp inve rted repeats of these six elements are highly similar and, with the ex ception of IS1295, their transposases exhibit moderate identities. In particular, the predicted amino-acid sequence of the transposase from IS1166 is 86% identical to that from the known transposable element IS 6120.