Gene cooption in mycobacteria and search for virulence attributes: comparative proteomic analyses of Mycobacterium tuberculosis, Mycobacterium indicus pranii and other mycobacteria.

Tuberculosis (TB), caused by Mycobacterium tuberculosis, is a leading infectious disease taking one human life every 15s globally. Mycobacterium undergoes reductive evolution; the ancestors have bigger genome size and rich in metabolic pathways. Mycobacterium indicus pranii (MIP) is placed much above Mycobacterium tuberculosis (M.tb) in evolutionary scale and is a non-pathogenic, saprophytic mycobacterium. Our in silico comparative proteomic analyses of virulence factors of M.tb and their homologs in 12 different Mycobacterial species, including MIP, point toward gene cooption as an important mechanism in evolution of mycobacteria. We propose that adaptive changes in niche factors of non-pathogenic mycobacterium, together with novel gene acquisitions, are key players in the evolution of pathogenicity. Antigenic analyses between M.tb and MIP highlighted the importance of PE/PPE family in host immunomodulation, further supporting the likely potential of MIP as an effective vaccine against TB.