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The Mycobacterium tuberculosis ?-oxidation genes echA5 and fadB3 are dispensable for growth in vitro and in vivo.

ABSTRACT: There are several lines of evidence pointing towards the importance of ?-oxidation in host survival of Mycobacterium tuberculosis including enormous gene redundancy for this process; approximately 100 genes are annotated as ?-oxidation genes for the five biochemical reactions that break down fatty acids into acetyl-CoA. Although most of these genes are predicted to be non-essential, two of the genes (echA5 and fadB3) are annotated as essential for growth in vitro, and therefore could be considered as putative drug targets. However, here we report the construction of echA5 and fadB3 null mutants confirming they are non-essential. No significant difference in growth between the mutant and parent strains was observed in either standard Middlebrook medium or in minimal medium supplemented with various carbon sources. Macrophage survival and mouse infection studies also showed no significant difference between the mutant and parent strains. Therefore, we conclude that these genes are dispensable for growth in vitro and in vivo.

SUBMITTER: Williams KJ

PROVIDER: S-EPMC3220763 | biostudies-literature | 2011 Nov

REPOSITORIES: biostudies-literature

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The Mycobacterium tuberculosis β-oxidation genes echA5 and fadB3 are dispensable for growth in vitro and in vivo.

Williams Kerstin J KJ Boshoff Helena I HI Krishnan Nitya N Gonzales Jacqueline J Schnappinger Dirk D Robertson Brian D BD

Tuberculosis (Edinburgh, Scotland) 20110718 6

There are several lines of evidence pointing towards the importance of β-oxidation in host survival of Mycobacterium tuberculosis including enormous gene redundancy for this process; approximately 100 genes are annotated as β-oxidation genes for the five biochemical reactions that break down fatty acids into acetyl-CoA. Although most of these genes are predicted to be non-essential, two of the genes (echA5 and fadB3) are annotated as essential for growth in vitro, and therefore could be consider ...[more]

PMID: 21764638

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Project description:ABSTRACT Triosephosphate isomerase (TPI) catalyzes the interconversion of dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate (G3P). This reaction is required for glycolysis and gluconeogenesis, and tpi has been predicted to be essential for growth of Mycobacterium tuberculosis. However, when studying a conditionally regulated tpi knockdown mutant, we noticed that depletion of TPI reduced growth of M. tuberculosis in media containing a single carbon source but not in media that contained both a glycolytic and a gluconeogenic carbon source. We used such two-carbon-source media to isolate a tpi deletion (?tpi) mutant. The ?tpi mutant did not survive with single carbon substrates but grew like wild-type (WT) M. tuberculosis in the presence of both a glycolytic and a gluconeogenic carbon source. (13)C metabolite tracing revealed the accumulation of TPI substrates in ?tpi and the absence of alternative triosephosphate isomerases and metabolic bypass reactions, which confirmed the requirement of TPI for glycolysis and gluconeogenesis in M. tuberculosis. The ?tpi strain was furthermore severely attenuated in the mouse model of tuberculosis, suggesting that M. tuberculosis cannot simultaneously access sufficient quantities of glycolytic and gluconeogenic carbon substrates to establish infection in mice. IMPORTANCE The importance of central carbon metabolism for the pathogenesis of M. tuberculosis has recently been recognized, but the consequences of depleting specific metabolic enzymes remain to be identified for many enzymes. We investigated triosephosphate isomerase (TPI) because it is central to both glycolysis and gluconeogenesis and had been predicted to be essential for growth of M. tuberculosis. This work identified metabolic conditions that make TPI dispensable for M. tuberculosis growth in culture and proved that M. tuberculosis relies on a single TPI enzyme and has no metabolic bypass for the TPI-dependent interconversion of dihydroxyacetone phosphate and glyceraldehyde-3-phosphate in glycolysis and gluconeogenesis. Finally, we demonstrate that TPI is essential for growth of the pathogen in mouse lungs.

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Dataset Information

The Mycobacterium tuberculosis ?-oxidation genes echA5 and fadB3 are dispensable for growth in vitro and in vivo.

Publications

The Mycobacterium tuberculosis β-oxidation genes echA5 and fadB3 are dispensable for growth in vitro and in vivo.

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