Genomic insights into the genus Mycobacterium

January 17, 2013
2:30 p.m.

The genus Mycobacterium is quite different from other bacterial genera. Major diversity concerns the cell wall structure, the duplication rate and the antimicrobial susceptibility. The genus arbor pathogens, like M. tuberculosis and M. leprae, and 150 opportunistic species occasionally responsible for human infections, mostly affecting lung, lymph nodes, cutis,  bones and joints; disseminated infections are also present, mainly in immunocompromised hosts.
Peculiar features of mycobacterial genome include the high G+C %, the high proportion of genes encoding enzymes involved in the lipid metabolism and the presence of genes encoding for two new families of proteins, PE and PPE, with putative antigenic activity. Very high is the proportion of repetitive DNA whose polymorphism may be investigated for genotyping purpose. Plasmids are present in a limited number of species and are not responsible of drug resistance.
Present knowledge of genus  Mycobacterium phylogeny is mainly based on the analysis of the genetic sequence of the 16S rRNA gene; in the last years studies based on concatenated sequences of major housekeeping genes have also been conducted but is nowadays clear that the actual Mycobacterium phylogeny still waits to be understood.