Engineered E. coli for PPIX and Heme Production

The strains used in this study are summarized in Additional file 1: Table S1. Molecular cloning and manipulation of plasmids were performed using E. coli DH5α. The plasmids and oligonucleotides used in this work are listed in Additional file 2: Tables S2 and Additional file 3: Table S3. For PPIX and heme fermentation, E. coli strain BL21 and MR-Fe20 medium were used. MR-Fe20 medium contained 6.67 g/L KH₂PO₄, 4 g/L (NH4)₂HPO₄, 0.8 g/L MgSO₄∙7H₂O, 0.8 g/L citric acid, 20 mg/L FeSO₄∙7H₂O, and 5 mL of trace metal solution A per liter. Trace metal solution A contained 0.5 mol of HCl, 2 g/L CaCl₂, 2.2 g/L ZnSO₄∙7H₂O, 0.5 g/L MnSO₄∙4H₂O, 1 g/L CuSO₄∙5H₂O, 0.1 g/L (NH₄)₆Mo₇O₂₄∙4H₂O, 0.02 g/L Na₂B₄O₇∙10H₂O, and 10 g/L FeSO₄∙7H₂O [25 (link)] (Additional file 4: Table S4).