Sulfide stress induces an enhanced growth phenotype in a Δsqr strain that is complemented by SQR expression. (A) Total medium sulfide measured as a function of time after dissolution of 0.2 mM NaHS into sterile growth medium (HHWm and thiosulfate) (blue filled circles) compared to the culture medium obtained from WT::pOS1 (green empty circles), Δsqr::pOS1 (red empty left triangles), and Δsqr::SQR (red filled left triangles) cell growth. The dashed line is a linear fit to the average value determined at each time point, revealing only a small, strain-independent decrease in the total sulfide concentration over the time course of each growth curve. (B) Average growth curves for wild-type (WT), Δsqr, and plasmid-complemented Δsqr::SQR S. aureus Newman strains grown on HHWm/thiosulfate medium in the absence of NaHS (−NaHS, empty symbols) and 0.2 mM NaHS (+NaSH, filled symbols) added at time zero: WT (black circles), Δsqr (red left triangles), and Δsqr::pSQR (blue diamonds). Error bars from triplicate experiments are shown for the NaHS-stressed WT, Δsqr, and Δsqr::pSQR strains only, for the sake of clarity.