WGS on second-line antibtuberculotics-challenged Mycobacterium smegmatis
Second-line antitubercular drugs, including bedaquiline, linezolid, and clofazimine, offer temporary solutions to the global challenge of drug-resistant tuberculosis. These drugs have divergent effects for bacteria, although the mechanism of action in case of clofazimine is not fully explored.The specific influence of these drugs on mycobacterial cellular homeostasis is a relevant and  yet unexplored area. Determining the impact of these drugs on the genome integrity of mycobacteria is particularly important from the perspective of resistance. In this study, we treated Mycobacterium smegmatis with subinhibitory concentrations of bedaquiline, linezolid, and clofazimine. We aimed to investigate the transcriptional changes in the DNA repair system by qPCR and the long-term mutator effect under antibiotic pressure by whole genome sequencing. Given that clofazimine binds to guanine, we also examined the effect of clofazimine treatment on the cellular dNTP levels. Our study uncovers that prolonged exposition to these drugs does not alter the mutation rate of Mycobacterium smegmatis significantly. Additionally, we observed specific activation patterns within the DNA repair system, and a notable decrease in dNTP levels triggered by clofazimine. This exploration of mycobacterial responses to these drugs contributes vital insights for the rational selection of drug-resistant TB treatments.