Figure 4. Plasmids do not mediate activation of SOS response.

Not all plasmids induce the SOS response in PAO1. The figure represents the area under the curve of luminescence production over OD₆₀₀ [AUC (lux/OD₆₀₀)] during the exponential phase of the growth curves of PAO1 WTplex:lux reporter strain, which encodes the luciferase operon under the control of an SOS inducible promoter (PAO1 in the figure). We also present the AUC (lux/OD₆₀₀) of the different plasmid-carrying WTplex:lux, and a control with the plasmid-free WTplex:lux growing in the presence of a sub-inhibitory concentration of the SOS-inducing antibiotic ciprofloxacin (45 μg/L). The bars indicate the average of 8 biological replicates and the error bars indicate the standard error. Asterisks indicate significant differences in SOS activation (Tukey’s post-hoc test, P< 0.05). As expected, plasmid pNUK73 and the presence of ciprofloxacin induced the SOS response. However, none of the remaining plasmids produced the activation of the stress response.