Figure 1

Example of effect of non-aureus staphylococci isolates on gene expression of Staphylococcus aureus. Tryptone soy agar plates (with erythromycin and X-gal) containing (A) the rnaIII::lacZ (SH101F7; Ery^r), (B) the hla::lacZ (PC322; Ery^r), or (C) the spa::lacZ (PC203; Ery^r) reporter strain of Staphylococcus aureus were exposed to 20 μL of either Supernatant (SP), Supernatant + Proteinase K (SPK), or Cell suspension (CS) obtained from overnight cultures of Staphylococcus chromogenes, Staphylococcus epidermidis, and Staphylococcus simulans, respectively. Staphylococcus schleiferi (strain 2898) [12] and H₂O were used as positive control (P) and negative control (N), respectively. Halos around the wells appeared between 12 and 36 h of incubation at 37 °C, and the diameter (measured in mm) was classified as NE: no effect (≤ 10 mm), SLE: slight effect (11–15 mm), ME: moderate effect (16–20 mm), and SE: severe effect (≥ 25 mm) on gene expression (upregulation for rnaIII and hla, and downregulation of spa). This figure is representative for all β-Galactosidase plate assays.