Mycobacterium tuberculosis (Mtb), a lung pathogen, is dependent on iron acquisition to successfully colonize the human host. Mtb secretes siderophores to acquire iron from host transferrin, ferritin and lactoferrin, but the siderophores cannot access iron in heme (Hm) or hemoglobin (Hb), which store greater than 75% of host iron. Recently, it was shown that the necrotic centers of TB granulomas (infected macrophages) contain high concentrations of host Hm- and Hb-sequestering proteins to limits access of Mtb to Hm iron.