A novel polymorphic genetic locus in members of the Mycobacterium tuberculosis complex

It has previously been shown that the P-AN promoter from Mycobacterium para tuberculosis can be used as a DNA probe to identify an RFLP between wild-ty pe Mycobacterium bovis and the vaccine strain Mycobacterium bovis BCC. To i nvestigate the genetic basis of this phenomenon, DNA fragments from a New Z ealand M. bovis cattle strain and M. bovis BCG Pasteur, containing the P-AN -binding region, were isolated from gene libraries, sequenced and character ized. Sequence analysis and comparison with database sequences showed that the P-AN region in M. bovis, M. bovis BCG sind Mycobacterium tuberculosis i s identical and shares 70% similarity to the P-AN sequence from M. paratube rculosis. The Shine-Dalgarno sequence and the -10 and -35 promoter regions are conserved between the different species. Analysis of the flanking seque nces of the P-AN region revealed that less than 1 kb downstream of P-AN is a 2405 bp fragment that is present in M. bovis BCG but absent in the M: bov is wild-type strain. The distribution of the 2405 bp fragment in members of the M. tuberculosis complex was investigated and found to be present in 70 out of 70 M. tuberculosis strains, and 7 out of 7 M. bovis BCC daughter st rains, 2 out of 2 Mycobacterium africanum strains, 2 out of 2 Mycobacterium microti strains and 7 out of 25 114. bovis strains. This is the first repo rt of a genetic region of M. bovis BCG that is not universally present in M . bovis strains. The fragment does not appear to be present in any mycobact erial species outside the IM. tuberculosis complex. It does not possess any characteristics of known transposable elements and the flanking sequences do not have any obvious features to suggest a deletion mechanism. The genet ic location of this region is close to the 3' end of the RD1 region of M. b ovis and 114. tuberculosis. The polymorphic nature of this locus in 114. bo vis will provide an additional genetic marker for strain differentiation.