Figure 8.

Phenotypes of the complementing strain of the ygaV mutant (Comp), which harbors the multicopy plasmid encoding ygaV gene: (A) Relative mRNA levels of ygaV in WT and the ygaV complementing strain as determined by quantitative real-time PCR analysis. The WT levels were set to 1.0. The gyrA gene was used as an internal standard. The values are means ± SD of three biological replicates. * p < 0.05, t test; (B) Promoter activities of the ygaVP operon. LacZ (β-galactosidase) activity measurement with the ygaV-lacZ fusion in WT, ygaV mutant and the complementing strain. Cells grown at mid-log phase (OD₆₀₀ = ~0.3) were treated or untreated with 0.2 mM Na₂S (final concentration) and harvested at late-log phase (OD₆₀₀ = 0.8~0.9). The values are means ± SD of three biological replicates; (C) H₂O₂ levels in WT, ygaV mutant and the complementing strain. Cells grown at mid-log phase (OD₆₀₀ = 0.5–0.6) were treated with 5.0 μg mL⁻¹ kanamycin (Km) (upper) or streptomycin (Sm) (bottom) (final concentration) for 5, 10 and 30 min, and then harvested. The values are means ± SD of three biological replicates; (D) Mean colony-forming-unit (CFU) values of WT, ygaV mutant and the complementing strain exposed to 0.2 μg mL⁻¹ or 1.0 μg mL⁻¹ Km or Sm (final concentration) for 30 min in the presence or absence of 0.2 mM Na₂S (final concentration). One of the CFU values of WT at 0.2 μg mL⁻¹ Km or Sm was set as 1. Different letters (a, b, c, d, e and f) indicate significant differences between groups (p < 0.05; Tukey’s test).