Fig. 1.

Relative fitness of wildtype strain (a) and its ∆dprA derivative (b) grown in head-to-head competitions against the DNA uptake-deficient ∆comB-F mutant. The competitions were treated with a combination of an initial UV pulse of 216 J m⁻² or no UV irradiation with a subsequent amendment of no DNA (DNase), homologous DNA or heterologous DNA. In each group n = 13. In the control competitions with no UV and no DNA both the wildtype and its ∆dprA derivative displayed a reduced fitness relative to KOM130 of w = 0.88 (0.83–0.92, 95% CI) and w = 0.86 (0.82–0.91, 95% CI), respectively, due to the biological cost of type IV pilus expression (Additional file 1: Fig. S1). Error bars indicate 95% confidence intervals. Significant differences between the treatment groups (pooled results of both UV- and UV+ competitions) are indicated by asterisks (** P < 0.001, *** P < 0.0001). A two-way ANOVA of all mean values is provided in (Additional file 1: Table S4)