In this project we present a comprehensive characterization and functional analysis of mycobacterial pgmA focusing on its role in central metabolic flux under different environmental conditions We further analysed its implication in disease biology and pathogenesis We have employed a combination of biochemical and genetic approaches to elucidate the functional properties of this key enzyme in mycobacteria
The primary challenge that we face in combating tuberculosis TB is understanding the long term disease and antibiotic persistence This has significant implications in the evolution of antimicrobial resistance AMR The survival of Mycobacterium tuberculosis Mtb within the host in a state of reduced metabolic activity has previously been linked to pathways involved in the synthesis of biomolecules such as triglycerides and glycogen Glycogen a form of nutrient storage is a highly conserved evolutionary mechanism found in both prokaryotes and eukaryotes However there is limited information regarding its role in TB disease progression and subsequent reactivation For this we conducted research using a Mtb strain lacking the pgmA gene which has been annotated as putative phosphoglucomutase A  crucial for glycogen metabolism Firstly the glycogen levels in pgmA mutant were found to have significantly fluctuated As expected under nutritionally modulating condition we observed a significant difference in the fitness of the pgmA null mutant strain compared to the wildtype strain Metabolome analysis conducted during nutritionally starving condition revealed an overrepresentation of proteolytic machinery in the pgmA deficient strain having impaired glycogen metabolism indicating a shift in the metabolome machinery to proteolysis The pgmA strain was found to be growing fine under normal growth conditions however it was found to be susceptible to most of the in vitro stresses This was found to be in line with the nutritionally challenging environment inside the THP1 macrophages and animal pathogenesis study The cytokine expression profiles reveal probable role of pgmA in antigen presentation inside the host This can be due to defects in cell architecture as suggested by our TEM analysis Further our lipid analysis by TLC reveals significant differences in the abundance of PDIM mycolic acid and triacylglycerol TAG between the wildtype and pgmA mutant strains Interestingly our preliminary data indicate that glycogen storage plays a crucial role in mycobacterial susceptibility toward different antibiotics in vitro ex vivo and in vivo Under severe nutrient deprivation the pgmA lacking strain was found to be significantly susceptible to antibiotic treatment as compared to wildtype and complement strain This highlights the involvement of the glycogen biosynthesis pathway in drug susceptibility Overall our study unveils the significance of glycogen homeostasis in mycobacterial persistence survival and reactivation This research contributes to our understanding of pathways involved in Mtb pathogenesis disease and antibiotic persistence Additionally it provides valuable insights for identifying novel drug targets against Mtb