A clinical mutation in <i>uvrA</i> , a DNA repair gene, confers survival advantage to <i>Mycobacterium tuberculosis</i> in the host

Abstract DNA repair pathways play an essential role in maintaining the genomic integrity of bacteria, and a perturbation in their biological activity helps bacteria survive under duress. In drug-resistant clinical strains, we identified a Q135K mutation in the uvrA gene, a DNA repair pathway gene. To delineate the role of uvrA and the Q135K mutation, we generated the gene replacement mutant of UvrA ( RvΔuvrA ) in Mycobacterium tuberculosis H37Rv ( Mtb-Rv ). While the lack of UvrA function in RvΔuvrA could be restored upon complementation with uvrA , the uvrA-Q135K mutant identified in clinical drug-resistant strains failed to do so. This was reflected in higher mutation rates in RvΔuvrA and RvΔuvrA::uvrA Q135A , compared with wild-type Rv or RvΔuvrA::uvrA complemented strains in the presence and absence of oxidative stress. Killing kinetics experiments with anti-TB drugs showed increased survival of RvΔuvrA and RvΔuvrA::uvrA Q135K , strains compared with Rv or RvΔuvrA::uvrA . Importantly, RvΔuvrA and RvΔuvrA::uvrA Q135K showed enhanced survival in peritoneal macrophages and murine infection model of infection. Together, data suggests that acquiring Q135K mutation benefits the pathogen, which helps enhance the host’s survival adaptability. Author Summary DNA repair mechanisms in an organism are necessary for correcting the errors generated during replication or when it is damaged/modified due to insults. As a GC organism, Mtb is highly prone to host-mediated attacks on its genome, which, if uncorrected, can impact its genome integrity. The drug-resistant clinical strains of Mtb harbor Q135K mutation in uvrA , the first enzyme in the nucleotide excision repair pathway. With the help of genetic, molecular, and murine challenge experiments, we show that the UvrA-Q135K mutation abrogates the enzyme’s activity, compromising the Mtb strain harboring the mutation in the oxidative and nitrosative stress. On the contrary, the mutation in UvrA imparts survival advantage in activated macrophages and murine infection models. Results presented argue that identified mutation helps in better adaptability in the host, which may include faster acquisition of drug resistance.