FIG 3.

Effects of hemH1 disruption and deletion on c-type cytochrome synthesis and nitrate reduction in PV-4. (a) Heme staining analyses of c-type cytochromes in the wild-type strain and hemH1 and hemH2 single mutants of S. loihica PV-4. After cell disruption, the supernatants containing the cellular protein fraction were resuspended in the SDS loading buffer without β-mercaptoethanol and then incubated at 37°C for 1 h. Molecular mass markers (in kilodaltons) are shown on the right. (b) Nitrate reduction of wild-type S. loihica PV-4 strain and the hemH1 deletion mutant. The parental strain carrying empty vector (PV-4/pHERD30T), the hemH1 deletion mutant carrying empty vector (PV4 ΔhemH1/pHERD30T), and the complementation strain carrying plasmid-borne hemH1 (PV4 ΔhemH1/pHERD30T-hemH1) were cultivated in the modified M1 minimal medium supplemented with 2 mM sodium nitrate under microoxic conditions (in tightly capped tubes without shaking). The blank represents the used culture medium without bacterial inoculation. The error bars represent the standard deviation (SD).