SRA

Increasing experimental evidence supports that Mycobacterium tuberculosis (Mtb) has evolved strategies to survive within the lysosomes from activated macrophages, which may represent a reservoir for persistent mycobacteria. To further our knowledge in Mtb response to the lysosomal environment, we profiled the global transcriptional activity of Mtb in a lysosomal in vitro exposure (LivE) model. At inhibitory conditions of lysosomal SF (iLivE), which did not kill but arrested mycobacterial replication thereby mimicking persistence, Mtb expresses a unique transcriptome, where genes involved in general stress response, metabolic reprogramming, cell wall remodeling, respiration, oxidative stress and dormancy response were found to be significantly modulated. Genes encoding for protein families involved in Mtb virulence including ESAT-6, PE-PPE and Mce proteins were also distinctly regulated. Extensive meta-analysis of the Mtb transcriptomes from iLivE and previously reported ex vivo, in vivo and in vitro stress models revealed most significant overlap between iLivE and primary murine macrophage infection model. Our study also highlighted the a-glucan synthesis pathway and a distinct set of toxin-antitoxin systems as toxicity mechanisms that could be exploited as novel antimicrobial approaches for intra-macrophage persistent bacilli. The specificity in responses generated in the LivE model was supported by the significant number of iLivE genes that did not overlap with any of the previously reported in vitro stress models. Finally, to validate the relevance of the LivE model, rv1258c encoding for the efflux pump protein Tap, was selected from the iLivE Mtb transcriptome for further characterization. An Mtb ?rv1258c mutant was constructed and displayed increased susceptibility to killing by lysosomal SF and by the antimicrobial peptide LL-37 found in lysosomes. Furthermore, ?rv1258c Mtb was attenuated in its ability to survive in primary murine macrophages.