Figure 1. Emergence of QS-mutants.

(a) growth of the A. tumefaciens C58 derivatives carrying the pTi-Gm (no conjugation and wild type low level QS-signal), pTi-traI::Gm (no conjugation and defective for QS-signal) and pTi-accR::Gm (constitutive AccR-regulon including conjugation and high level QS-signal). The constitutively conjugating strain had significantly lower carrying capacity than the other two strains that did not differ (F_(2,94) = 22.36, p < 0.0001, for difference in overall optical density, indicated by an asterisk). The three experimental blocks did not differ significantly F_(2,94) = 2.74, p = 0.07. The r² for the model = 0.88. (a) main characteristics of the analysed QS-altered mutants (#6, #37, #44, #47, #56, #66, #73, #78, #91, #110 and #137) deriving from the A. tumefaciens C58 (pTi-accR::Gm) ancestor, and the A. tumefaciens C58 (pTi-Gm). In this assay, pTi conjugation was performed in the absence of agrocinopine. NA, non-applicable. (c) growth of the A. tumefaciens C58 clones carrying the pTi-Gm and pTi-accR::Gm, of the evolved QS-altered mutants (#6, #37, #44, #47, #56, #66, #73, #78, #91, #110 and #137) and of two evolved clones (#20, #113) that retained ancestral QS-production. Evolved QS-altered mutants had significantly (indicated by an asterisk) more rapid growth than evolved (clones #20, #113) or ancestral (pTi-accR::Gm) clones with high QS-signal production; analysis performed on square-root transformed optical density, respective slopes ± SE for increase in optical density over time 0.0376 ± 0.0007 and 0.0288± 0.0013; interaction time x bacterial genotype F_(1,161) = 62.01, p < 0.0001. The two experimental blocks did not differ significantly F_(1,161) = 0.27, p = 0.60. The r² for the model = 0.97. (d) Ti-plasmid conjugation of the clone #73 in the absence and presence of additional QS-signal (500 nM). Letters indicate statistically different levels of Ti-plasmid transconjugants (Kruskal-Wallis, p < 0.05, n = 3).