Cooperation activation was delayed due to the presence of <i>lasR</i> mutant.

<p>(A) The same amounts of wild type (WT) <i>P. aeruginosa</i> PAO1 were cultured in different volumes of LB broth medium. (B) 10<b> </b>µl of overnight cultivated WT PAO1, 5<b> </b>µl WT PAO1+5<b> </b>µl PAO1-<i>ΔlasR</i>, and 10<b> </b>µl PAO1-<i>ΔlasR</i> strains were independently cultured in the same volume of LB broth medium. Activation of cooperation (☆) was determined by significantly increased expression of <i>lasB</i> gene. Data are means ± SEM, and representative of three experiments. *, <i>P</i><0.05, one-way ANOVA (Tukey-Kramer post hoc).