IDENTIFICATION OF AN INSERTION SEQUENCE-LIKE ELEMENT IN A SUBSPECIES OF MYCOBACTERIUM-KANSASII

Analysis of a genomic DNA clone library of a strain from the genetic s ubspecies of Mycobacterium kansasii determined the existence of a repe titive insertion sequence-like element. The element is 947 bp long and is present in a minimum of 1 to 11 copies per genome. Similar to inse rtion sequences, it contains a 3-bp (TAG) direct repeat at its extremi ties and a transcription promoter-like sequence. In addition, for one of the clones sequenced, a potential cointegrate formation, a characte ristic frequently observed with insertion sequences, was revealed. Thi s insertion sequence does not contain short inverted repeats near the ends or a large open reading frame to code for a transposase enzyme. I ts host range is restricted to a previously described genetic subspeci es of M. kansasii and is not present in typical M. kansasii or other m ycobacterial species. When used as a probe for Southern blot hybridiza tion, significant heterogeneity between different isolates of the M. k ansasii subspecies was observed. This repeated element will be useful in further studies on the characterization, diagnosis, and epidemiolog y of M. kansasii.