CHARACTERIZATION OF AN IS-LIKE ELEMENT FROM MYCOBACTERIUM-TUBERCULOSIS

A DNA sequence, present in members of the Mycobacterium tuberculosis c omplex, has been identified and characterized. The distribution of thi s DNA sequence among mycobacterial species was analysed by DNA hybridi zation and PCR experiments. As the sequence was detected only in bacte ria belonging to the M. tuberculosis complex, it may be useful for the rapid discrimination of mycobacteria. Interestingly, the sequence has some characteristics of an insertion element (IS) and codes for a hyp othetical protein with significant homologies to proteins encoded by s everal IS elements of other organisms, namely IS427 and IS869 from Agr obacterium tumefaciens, IS402 from Pseudomonas cepacia, Tn4811 from St reptomyces lividans and ISRm4 from Rhizobium meliloti. Together, these elements form a previously unrecognized family of transposable elemen ts. This finding suggests the possibility of horizontal gene transfer between pathogenic mycobacteria and other organisms including Gram-neg ative plant-pathogenic bacteria.