Fig. 2: Effect of tarO deletion on virulence gene expression and on the virulence potential of USA300.
From: Modulation of MRSA virulence gene expression by the wall teichoic acid enzyme TarO
a Relative psmα3 transcripts in S. aureus strains grown in TSB medium supplemented with (+) or without (−) tunicamycin (Tuni, 0.5 μg/ml) for 3 h, presented as relative expression levels (log2 fold changes) compared with the tunicamycin-untreated WT USA300. Data represent mean ± SD from three independent experiments. b, c Representative images (b) and quantitative analysis (c) of Western blotting for SpA in S. aureus strains grown in TSB medium supplemented with (+) or without (−) tunicamycin (0.5 μg/ml) for 3 h. Band intensity of SpA was normalized to the intensities obtained with loading control SrtA, and the results are reported as relative expression levels (log2 fold changes) compared with the tunicamycin-untreated WT USA300. Data represent mean ± SD from n = 3 independent experiments. d The overlap of tarO-activated genes (upper panel) and tarO-repressed genes (lower panel) between the 1.5- and 3-h time points. e–h Genes (or operons) modulated by tarO at the 3-h time point. The minus symbol indicates downregulation upon tarO deletion, the numbers indicate the fold change relative to the WT USA300 LAC control. i Survival rates of G. mellonella larvae upon infection by S. aureus strains. j Virulence of USA300 and ΔtarO strains. The female BALB/c mice were challenged with 5 × 106 CFU (n = 15 for USA300 and ΔtarO strains) or 2 × 107 CFU (n = 14 for USA300, n = 15 for ΔtarO). Horizontal bars (in red) indicate observation means. k Survival rates of female BALB/c mice upon infection by WT USA300 LAC strain and ΔtarO mutant. Statistical analysis was performed using two-tailed one-sample t-test (when compared with the tunicamycin-untreated WT USA300 control, which was set to a fold change of 1) or otherwise with Student’s two-tailed unpaired t-test (in a and c), log-rank test (in i and k), and Mann–Whitney two-tailed test (in j). In (a, b, c, and i), USA300 and ΔtarO strains harbor an empty pYJ335-1 vector as control.
