The ESX-4 type VII secretion system in required for efficient heme utilization by Mycobacterium tuberculosis

In this study our primary objective was to identify unknown components that are required of Mtb Hm acquisition. Herein, we show that the ancestral ESX-4 type VII secretion system (T7SS) which was thought to be inactive in Mtb is required for efficient Hm utilization. We also identified that the culture filtrate proteins Rv0125 and Rv1085c and the alternative sigma factor SigM are necessary of Hm utilization. Finally, we present the first direct evidence that some mycobacterial PPE proteins are pore forming membrane proteins.