Figure 2. Kinetics of sRNA expression in vitro.

Clinical S. aureus strains were grown in BH media until mid (OD₅₅₀ = 0.5) (open triangle) or late-exponential (OD₅₅₀ = 6) (plain shape) growth phases. Total RNA was extracted, and the sRNA transcripts were quantified by RT-PCR normalized to the level of gyrB mRNA expression. The results are presented according to the isolation sites of the 60 strains: 20 abscesses (Ab), 20 cystic fibrosis sputa (CF) and 20 nasal (No). The results represent the mean of 2 replicate experiments. The bars indicate geometric mean values. *For each sRNA, statistically significant differences (Mann Whitney, p<0.05) between the level of expression in mid or in late-exponential growth phase and the origin of the isolate are indicated.