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Unrestrained long-chain fatty acid catabolism kills Mycobacterium tuberculosis

T Beites(2) D Schnappinger(1) S Ehrt(1)

1:Weill Cornell Medical College; 2:i3S - Instituto de Investigação e Inovação em Saúde da Universidade do Porto

Mycobacterium tuberculosis thrives in infection foci that are notorious for lipid accumulation, setting the selective pressure for preferential usage of lipids, including long-chain free fatty acids (LC-FFA) and cholesterol, as carbon sources. Importantly, this lipid-based diet prompts M. tuberculosis to acquire a drug tolerant phenotype. However, host lipids, in specific LC-FFA, are potent antimicrobial agents, leading to the question of how M. tuberculosis evades this effect. In previous work, we have identified the respiratory enzyme type-2 NADH dehydrogenase and the membrane oxidoreductase EtfD as necessary for LC-FFA resistance and for full virulence. This illustrates the ability of turning a favorable environment to M. tuberculosis into a toxic one. Building on these results, we performed transposon sequencing to identify the full scope of M. tuberculosis LC-FFA resistant factors. Sequencing statistical analysis identified 38 genes associated with LC-FFA resistance spanning different metabolic pathways/ cell processes, including cell wall components biosynthesis, cyclic AMP signaling and folate cycle. Next, we performed a functional “deep dive” on the screen’s top hit – a universal stress protein of unknown function. Absence of this protein led to a dramatic increase in LC-FFA catabolism associated with oxidative phosphorylation perturbations and to a pronounced survival defect in the chronic phase of infection in C57BL/6 mice. These results indicate that this universal stress protein is an essential regulator of M. tuberculosis metabolism during infection.

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