Inhibition of de novo fatty acid synthesis in Mycobacterium tuberculosis
De novo fatty acid synthesis produces the acyl units needed to generate phospholipids, lipoproteins, enzyme prosthetic factors, polyketides, and mycolic acids in Mycobacterium tuberculosis (Mtb). Here, we identifed sALT629, a novel butoxyphenyl-tetrazole-acetamide compound that inhibits de novo lipid synthesis in Mtb. This compound disrupts the Mtb lipidome and prevents incorporation of metabolic tracers into acyl chains of Mtb lipids. Unexpectedly, we also found that sALT629 treatment significantly depleted triacylglycerol (TAG) pools as a metabolic compensation mechanism when de novo fatty acid synthesis was inhibited. Resistance to sALT629 was mediated by loss of function mutations in HadC, the non-essential hydroxyacyl-ACP-dehydratase subunit involved in the synthesis of long-chain oxygenated mycolic acids. Inactivating HadC rescued sALT629-mediated inhibition by sustaining TAG pools to fulfill Mtb's biosynthetic demand for acyl chains. Lastly, loss of function HadC resistance mutations resulted in cell wall perturbations that confer fitness defects in vitro and in vivo suggesting that this specific resistance mechanism is unlikely to arise in Mtb in a clinical setting. Overall design: RNA-seq of WT Mtb treated with different antitubercular compounds (sALT629, INH, and ISO) for 4 hours in standard rich medium.