Rewiring of Metabolic Network in Mycobacterium tuberculosis During Adaptation to Different Stresses

Abstract

Metabolic adaptation of Mycobacterium tuberculosis (M. tuberculosis) to microbicidal intracellular environment of host macrophages is fundamental to its pathogenicity. However, an in-depth understanding of metabolic adjustments through key reaction pathways and networks is limited. To understand how such changes occur, we measured the cellular metabolome of M. tuberculosis subjected to four microbicidal stresses using liquid chromatography-mass spectrometric multiple reactions monitoring (LC-MRM/MS). Overall, 87 metabolites were identified. The metabolites best describing the separation between stresses were identified through multivariate analysis. The coupling of the metabolite measurements with existing genome-scale metabolic model, and using constraint-based simulation led to several new concepts and unreported observations in M. tuberculosis; such as (i) the high levels of released ammonia as an adaptive response to acidic stress was due to increased flux through L-asparaginase rather than urease activity; (ii) nutrient starvation-induced anaplerotic pathway for generation of TCA intermediates from phosphoenolpyruvate using phosphoenolpyruvate kinase; (iii) quenching of protons through GABA shunt pathway or sugar alcohols as possible mechanisms of early adaptation to acidic and oxidative stresses; and (iv) usage of alternate cofactors by the same enzyme as a possible mechanism of rewiring metabolic pathways to overcome stresses. Besides providing new leads and important nodes that can be used for designing intervention strategies, the study advocates the strength of applying flux balance analyses coupled with metabolomics to get a global picture of complex metabolic adjustments.

Active and prospective latent tuberculosis are associated with different metabolomic profiles: clinical potential for the identification of rapid and non-invasive biomarkers

“…Mycothiol is used by mycobacteria to maintain an intracellular reducing environment and to protect against cellular damage from oxidative species and xenobiotics [ 34–36 ]. In this context, results from a recent metabolomics study in M. tb suggested perturbations in cysteine metabolism under microbicidal stresses [ 37 ]. Finally, it has been reported that free unsaturated fatty acids, including arachidonic acid, can stimulate the activation of dormant M. tb cells in liquid medium [ 30 ].…”

Metabolic Versatility of Mycobacterium tuberculosis during Infection and Dormancy

“…Specifically, PckA connects oxaloacetate to phosphoenolpyruvic acid (PEP) ( Figure 1 B, dark red arrows), while Icl1 allows the bypassing of the oxidative branch of the TCA cycle and funnel metabolism towards the glyoxylate shunt ( Figure 1 B, red arrows). The involvement of the anaplerotic node is also evident during nutrient stress, where phosphoenolpyruvate kinase is linked to the production of TCA intermediates from phosphoenolpyruvate [ 71 ].…”

SAR Analysis of Small Molecules Interfering with Energy-Metabolism in Mycobacterium tuberculosis

“…M. tuberculosis spends most of its life inside the host cell in a state of slowed or arrested replication. Even as a non-replicating bacilli with minimal metabolic activity, Mtb has evolved unique metabolic adaptability to the host-imposed stringent niches in order to preserve its survival and ability to ensure transmission to a new host [ 130 ]. CCM provides energy and essential biosynthetic precursors, thus playing a key role in Mtb pathogenicity [ 131 ], and Mtb demonstrated the ability to use a plethora of organic substrates, such as carbohydrates, lipids, amino acids, and simple organic acids, to fuel it.…”