Fig. 6

Effects of hemH1 and hemH2 double deletions on c-type cytochrome synthesis and nitrate reduction in S. oneidensis MR-1. a Bacteria were cultivated in the modified M1 minimal media supplemented with 2 mM sodium nitrate under microoxic conditions (in tightly capped tubes incubated without shaking). The blank represents the culture media without bacterial inoculation. Error bars represent SD; b Hemin could rescue the nitrate reduction capacity of MR-1ΔhemH1ΔhemH2 under microoxic conditions; c The effect of different hemin concentration(0, 0.1, 1, 10 μg/ml) on nitration reduction in hemH1-hemH2 double mutant strain MR-1ΔhemH1ΔhemH2 under microoxic conditions; d Effects of hemH1-hemH2 double deletion on c-type cytochrome synthesis in MR-1. Total protein (left) content and Heme staining (right) analyses of c-type cytochromes in the following stains: MR-1 wild-type, MR-1ΔhemH1, MR-1ΔhemH2, MR-1ΔhemH1ΔhemH2 (2X means the double quantity of sample). After cell disruption, the supernatants containing the cellular protein fraction were resuspended in the SDS loading buffer and then incubated at 37 °C for 1 h; e Top panel: The CymA protein content of the wild-type strain MR-1 cells is ∼2-fold higher than that of the double mutant MR-1ΔhemH1ΔhemH2 cells, but the heme-staining analyses showed that the CymA protein were not detected. Cells were grown in M1 medium supplemented with 2 mM sodium nitrate and 0.1 μg/ml hemin under microoxic conditions, and CymA protein content was quantified by using western blotting and densitometry. The lanes contained equivalent total proteins. Bottom panel: The Real-time PCR analyses of napB and cymA transcripts in MR-1 and MR-1ΔhemH1hemH2 strains