Integrated multi-omic analysis of M. tuberculosis H37Ra redefines virulence attributes

M. tuberculosis H37Ra, an avirulent tubercle bacillus, is a commonly used model to investigate virulence attenuation in M. tuberculosis. Comparative high-throughput studies have earlier correlated its avirulence to the presence of specific mutations or absence of certain proteins. However, a recent sequencing study of H37Ra has disproved several genomic differences earlier reported to be associated with virulence. This warrants further investigations on the H37Ra proteome as well. In this study, we carried out an integrated analysis of the genome, transcriptome and proteome of H37Ra. In addition to confirming single nucleotide variations and insertion-deletions that were reported earlier, our study provides novel insights into the mutation spectrum in the promoter regions of 7 genes. In all, we provide protein coding evidence for 3,199 proteins representing ~79% of the total predicted gene count. Transcriptome analysis revealed the expression of 3,945 high-confidence transcripts including several transcripts mapping to the genome that were previously thought to be non-coding. We identified 9 genes whose coding potential was hitherto reported to be absent in H37Ra . These include 2 putative virulence factors belonging to ESAT-6 like family of proteins. Furthermore, proteogenomic analysis enabled us to identify 63 novel proteins coding genes and correct 25 existing gene models in H37Ra genome. A majority of these were found to be conserved in the virulent strain H37Rv as well as in other mycobacterial sp. suggesting that that the differences in the virulent and avirulent strains of M. tuberculosis are not entirely dependent on the expression of certain proteins or their absence but may possibly be ascertained to functional changes.