The genetics of Mycobacterium tuberculosis

Gene manipulation in Mycobacterium tuberculosis has been slow in coming of age owing to the inherent difficulties associated with working on this aero sol-transmitted pathogen, in addition to the paucity of molecular tools suc h as plasmids and transposons. One of the early approaches to overcome thes e difficulties was the development of phasmids, which combined the properti es of phages and plasmids and allowed introduction of recombinant genes int o mycobacteria. The lone plasmid pAL5000 of mycobacteria has been exploited to its fullest potential in the construction of a plethora of vectors. Abo ve all, the single most important achievement has been the development of e legant and innovative approaches to overcome the problem of illegitimate re combination which threatened the success of allelic-exchange mutagenesis in the slow-growing pathogenic mycobacterial species. In this review I discus s the current status of conditionally replicating plasmid and transposon ve ctors and their application in generating targeted mutations in mycobacteri a.