Understanding Metabolic Remodeling in Mycobacterium smegmatis to Overcome Energy Exigency and Reductive Stress Under Energy-Compromised State

Abstract

Mycobacteria such as Mycobacterium tuberculosis, the causative agent of tuberculosis that annually kills several million people worldwide, and Mycobacterium smegmatis, the non-pathogenic fast-growing mycobacteria, require oxidative phosphorylation to meet their energy requirements. We have previously shown that deletion of one of the two copies of atpD gene that codes for the ATP synthase β-subunit establishes an energy-compromised state in M. smegmatis. Here we report that upon such deletion, a major routing of electron flux occurs through the less energy-efficient complexes of its respiratory chain. ΔatpD bacterium also shows an increased reduced state which is further confirmed by the overexpression of WhiB3, a major redox sensor. We show a substantial modulation of the biosynthesis of cell wall associated lipids and triacylglycerol (TAG). An accumulation of TAG-containing lipid bodies is further confirmed by using 14C oleate incorporation. Interestingly, the mutant also shows an overexpression of TAG-degrading lipase genes, and the intracellular lipolytic enzymes mediate TAG hydrolysis for their utilization as energy source. We believe that our in vitro energy-depleted model will allow us to explore the critical link between energy metabolism, redox homeostasis, and lipid biosynthesis during ATP-depleted state, which will enhance our understanding of the bacterial adaptation, and will allow us to identify novel drug targets to counter mycobacterial infections.

Uncovering the roles of Mycobacterium tuberculosis melH in redox and bioenergetic homeostasis: implications for antitubercular therapy

“…These data point toward a role for melH deletion causing NAD(H) depletion, further contributing to an inability to maintain redox homeostasis. Mycobacterium smegmatis Δ atpD exhibits reduced ATP levels, accompanied by elevated levels of ROS and significant alterations in NAD levels, indicating an imbalanced redox state within the cell ( 46 ). This study demonstrated a threefold upregulation of whiB3 in M. smegmatis Δ atpD compared to the WT.…”

Advances in computational frameworks in the fight against TB: The way forward

“…Several compounds have been identified during the last few years with potential anti-tubular properties and are currently undergoing preclinical and clinical studies like, bedaquiline ( Antoci et al, 2021 ; Chakraborti et al, 2021 ; Patil & Jain, 2021 ; Deshkar & Shirure, 2022 ), PA-824 ( Lenaerts et al, 2005 ; Edwards & Field, 2022 ; Xu et al, 2022 ; Yan et al, 2022 ), and delamanid ( Skripconoka et al, 2013 ; Liu et al, 2018 ; Nasiri et al, 2022 ). Existing drugs have also been modified to repurpose them against TB and they include -riminophenazines ( Valinetz et al, 2020 ; Brunaugh et al, 2022 ), b-lactams ( Moon et al, 2018 ; Story-Roller & Lamichhane, 2018 ; Ur Rahman et al, 2018 ), and oxazolidinones ( Balasubramanian et al, 2014 ; Alghamdi et al, 2020 ; Margaryan et al, 2022 ; Ndukwe et al, 2022 ).…”

Structure and regulation of the mycobacterial F1-ATPase

“…Thus, leading to increased rates of ATP synthesis and higher metabolic flux at a low energetic expense [56]. In harsh conditions, studies have shown that NDH-1 was downregulated, while ndh genes were upregulated in M. smegmatis [67]. This was also observed in the double deletion of ndh and ndhA which led to the death of the bacteria [55].…”