Multiple acyl-CoA dehydrogenase deficiency kills <i>Mycobacterium tuberculosis</i> in vitro and during infection

ABSTRACT The human pathogen Mycobacterium tuberculosis (Mtb) devotes a significant fraction of its genome to fatty acid metabolism. Although Mtb depends on host fatty acids as a carbon source, fatty acid β-oxidation is mediated by genetically redundant enzymes, which has hampered the development of antitubercular drugs targeting this metabolic pathway. Here, we identify rv0338c , referred to as etfD Mtb , to encode a membrane dehydrogenase essential for fatty acid β-oxidation in Mtb. An etfD deletion mutant (Δ etfD ) was incapable of growing on fatty acids in vitro, with long-chain fatty acids being bactericidal, and failed to grow and survive in mice. The Δ etfD metabolome revealed a block in β-oxidation at the step catalyzed by acyl-CoA dehydrogenases (ACADs). In many organisms, including humans, ACADs are functionally dependent on an electron transfer flavoprotein (ETF) and cognate dehydrogenase. Immunoprecipitation identified EtfD in complex with FixA (EtfB Mtb ). FixA (EtfB Mtb ) and FixB (EtfA Mtb ) are homologous to the human ETF subunits. Our results demonstrate that EtfBA Mtb constitutes Mtb’s ETF, while EtfD Mtb , although not homologous to human EtfD, functions as the dehydrogenase. These findings identify Mtb’s fatty acid β-oxidation as a novel potential target for TB drug development.