Depletion of M. tuberculosis GlmU from Infected Murine Lungs Effects the Clearance of the Pathogen

M. tuberculosis N-acetyl-glucosamine-1-phosphate uridyltransferase (GlmU(Mtb)) is a bi-functional enzyme engaged in the synthesis of two metabolic intermediates N-acetylglucosamine-1-phosphate (GlcNAc-1-P) and UDP-GlcNAc, catalyzed by the C- and N-terminal domains respectively. UDP-GlcNAc is a key metabolite essential for the synthesis of peptidoglycan, disaccharide linker, arabinogalactan and mycothiols. While glmU (Mtb) was predicted to be an essential gene, till date the role of GlmU(Mtb) in modulating the in vitro growth of Mtb or its role in survival of pathogen ex vivo / in vivo have not been deciphered. Here we present the results of a comprehensive study dissecting the role of GlmU(Mtb) in arbitrating the survival of the pathogen both in vitro and in vivo. We find that absence of GlmU(Mtb) leads to extensive perturbation of bacterial morphology and substantial reduction in cell wall thickness under normoxic as well as hypoxic conditions. Complementation studies show that the acetyl- and uridyl- transferase activities of GlmU(Mtb) are independently essential for bacterial survival in vitro, and GlmU(Mtb) is also found to be essential for mycobacterial survival in THP-1 cells as well as in guinea pigs. Depletion of GlmU(Mtb) from infected murine lungs, four weeks post infection, led to significant reduction in the bacillary load. The administration of Oxa33, a novel oxazolidine derivative that specifically inhibits GlmU(Mtb), to infected mice resulted in significant decrease in the bacillary load. Thus our study establishes GlmU(Mtb) as a strong candidate for intervention measures against established tuberculosis infections.