pH dependent direct sulfhydrylation pathway is required for pathogenesis of Mycobacterium tuberculosis

Methionine is essential for the survival of Mycobacterium tuberculosis ( M. tuberculosis ) inside the host. Inhibiting the transsulfuration pathway fails to exhibit methionine auxotrophy suggesting the presence of an alternate methionine biosynthesis pathway in M. tuberculosis . Orthologues of MetZ _TB in other bacterial species are known to regulate a redundant single step methionine biosynthesis pathway known as direct sulfhydrylation. Genetic disruption of the metZ -mediated direct sulfhydrylation pathway impaired the ability of M. tuberculosis to survive inside macrophages. Further, we demonstrated that direct sulfhydrylation pathway is indispensable for the survival at low pH. Using in-silico molecular docking and MD simulations studies we showed that the active site of MetZ binds substrate O-succinyl homoserine (OSH) more tightly at acidic rather than neutral pH. Intriguingly, despite higher intracellular ATP levels, a relative decrease in the frequency of generation of Bedaquiline (BDQ)-induced persisters in ΔmetZ suggests a role of direct sulfhydrylation pathway in modulating BDQ sensitivity in M. tuberculosis . Finally, using an animal model, we demonstrated that absence of metZ impeded the ability of M. tuberculosis to grow inside the host. Our findings suggest that administering inhibitors of metZ as an adjunct can be explored as a strategy to potentiate BDQ as a novel anti-TB regimen.