Fig. 1

Effects of hemH1 and hemH2 double deletions on phenotypes of S. oneidensis MR-1. a The heme biosynthesis pathway; b Organization of the ferrochelatase genes hemH1 and hemH2 in S. loihica PV-4 and S. oneidensis MR-1. The operon encodes a periplasmic glutathione peroxidase (SO_3349) and a ferrochelatase paralogue (hemH2) in strain MR-1 while the former is absent in strain PV-4; c Inactivation of both ferrochelatase genes (hemH1 and hemH2) resulted in overproduction of protoporphyrin IX in MR-1. Cell colonies grown from a droplet of mid-log-phase culture (OD₆₀₀ of ~ 0.2) for each indicated strain on LB plates (supplemented with 10 μg/ml of hemin), the hemH1 and hemH2 double mutant exhibited a red-color phenotype while deletion of either hemH1 or hemH2 did not cause the same phenotypic change. In the genetic complementation analyses on the PPIX-overproducing hemH1 deletion mutant PV-4ΔhemH1, the plasmid-borne wild-type hemH1 or hemH2 gene restored the phenotype of the mutant to the same pink color of the wild-type strain carrying the empty vector