Identification of a diacylglycerol acyltransferase gene involved in accumulation of triacylglycerol in Mycobacterium tuberculosis under stress

Abstract

Mycobacterium tuberculosis under stress stores triacylglycerol (TG). There are 15 genes in M. tuberculosis that belong to a novel family of TG synthase genes (tgs), but it is not known which of them is responsible for this accumulation of TG. In this paper, it is reported that M. tuberculosis H37Rv accumulated TG under acidic, static or hypoxic growth conditions, or upon treatment with NO, whereas TG accumulation was drastically reduced in the tgs1 (Rv3130c) disrupted mutant. Complementation with tgs1 restored this TG accumulation. C 26 was a major fatty acid in this TG, indicating that the TGS1 gene product uses C 26 fatty acid, which is known to be produced by the mycobacterial fatty acid synthase. TGS1 expressed in Escherichia coli preferred C 26 : 0 -CoA for TG synthesis. If TG storage is needed for the long-term survival of M. tuberculosis under dormant conditions, the tgs1 product could be a suitable target for antilatency drugs.

Lipidomic analyses of Mycobacterium tuberculosis based on accurate mass measurements and the novel “Mtb LipidDB”

“…The abundance and biological importance of the Mtb lipids has resulted in extensive and elegant studies to elucidate their structures and functions ( 1-3 ). In many cases, the lipids of Mtb are unique to this pathogen or shared only with other members of this genus.Earlier studies demonstrate variability in lipid profi les among different strains of Mtb ( 7-11 ) and that minor variations in the structure of individual lipids can occur with changes in the growth environment (12)(13)(14)(15)(16)(17)(18)(19)(20). However, targeted and nontargeted assays that monitor changes in Mtb lipid profi les are generally performed by traditional TLC-based methods ( 21 ), and global lipidomics analyses in Mtb have been restricted due to limits in the technology to detect and rapidly identify a large number of lipids in a single experiment.…”

Metabolism of Plasma Membrane Lipids in Mycobacteria and Corynebacteria

“…Recent evidence suggests that M. tuberculosis accumulates TAG-based lipid droplets while residing in macrophages using fatty acids released from host TAGs, and this process is critical for acquiring a dormancy phenotype [53]. Nevertheless, a mutant defective in accumulating TAG remained viable under in vitro dormancy-inducing conditions [54]. These somewhat contradictory observations suggest that our understanding of TAG metabolism in mycobacteria is far from complete.…”

“…For example, the M. tuberculosis genome encodes 15 putative TAG synthetase genes [48,80]. Despite the redundancies, recent studies reported that some of these tgs genes are critical for TAG synthesis in M. tuberculosis [48,54]. Specifically, TAG synthetases encoded by Rv3130c (tgs1), Rv3734c (tgs2), Rv3234c (tgs3), and Rv3088 (tgs4) have been shown to have TAG synthetase activities [53].…”

Interplay of human macrophages and Mycobacterium tuberculosis phenotypes

“…The study authors further attempted to model the transcriptomic results using bacteria growing according to the Wayne model, but besides dosR induction, in vitro phenotypes did only poorly recapitulate sputum patterns [319]. One of the upregulated genes in the dosR regulon, tgs1, encodes a triacylglycerol synthase involved in the accumulation of TAG-containing lipid droplets inside the Mtb cytosol [321]. Staining of sputum samples for lipids revealed lipid droplet accumulation in sputum bacteria [319,322] reminiscent of stressed or dormant Mtb phenotypes [290,321] and of bacilli in foamy macrophages [288].…”

“…One of the upregulated genes in the dosR regulon, tgs1, encodes a triacylglycerol synthase involved in the accumulation of TAG-containing lipid droplets inside the Mtb cytosol [321]. Staining of sputum samples for lipids revealed lipid droplet accumulation in sputum bacteria [319,322] reminiscent of stressed or dormant Mtb phenotypes [290,321] and of bacilli in foamy macrophages [288]. Furthermore, time to positivity of sputum samples correlated with the proportion of lipid droplet-positive bacteria [319], indicating that this subpopulation requires more time to resume growth upon inoculation into broth.…”