Impaired fatty acid import and metabolism in macrophages restricts intracellular growth of Mycobacterium tuberculosis

Mycobacterium tuberculosis (Mtb) infection of macrophages reprograms cellular lipid metabolism to promote the formation of cytosolic lipid droplets. While it is clearly known that intracellular Mtb utilize host derived fatty acids and cholesterol to fuel a majority of its biosynthetic demands, the role of macrophage lipid metabolism on the bacteria’s ability to access the intracellular lipid pool remains controversial. We have utilized a CRISPR genetic knockdown approach to, systematically and comprehensively, characterize the role of macrophage fatty acid metabolism on the intracellular growth of Mtb. Our analyzes demonstrate that knockdown of lipid import, sequestration and metabolism genes collectively impair the intracellular growth of Mtb in macrophages. We further demonstrate that modulating fatty acids homeostasis in macrophages impair Mtb replication by enhancing production of pro-inflammatory cytokines, restricting the bacteria access to nutrients and increasing oxidative stress in a manner which is surprisingly divergent. We also demonstrate that impaired macrophage lipid droplet biogenesis is restrictive to intracellular Mtb growth. However, increased induction of lipid droplet formation by downstream blockade of fatty acid oxidation does not rescue the impaired Mtb growth phenotypes. Our work provides a characterization of macrophage fatty acid homeostasis and how its modulation impacts Mtb intracellular growth.