Characterization of an IS-like element from Mycobacterium tuberculosis.

A DNA sequence, present in members of the Mycobacterium tuberculosis complex, has been identified and characterized. The distribution of this DNA sequence among mycobacterial species was analysed by DNA hybridization and PCR experiments. As the sequence was detected only in bacteria 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 hypothetical protein with significant homologies to proteins encoded by several IS elements of other organisms, namely IS427 and IS869 from Agrobacterium tumefaciens, IS402 from Pseudomonas cepacia, Tn4811 from Streptomyces lividans and ISRm4 from Rhizobium meliloti. Together, these elements form a previously unrecognized family of transposable elements. This finding suggests the possibility of horizontal gene transfer between pathogenic mycobacteria and other organisms including Gram-negative plant-pathogenic bacteria.