Effect of the overexpression of PA4781 on c-di-GMP levels in <i>E. coli</i>.

<p>(A) Comparison of c-di-GMP levels of the <i>E</i>. <i>coli</i> AB1548 mutant strain, lacking the endogenous PDE YhjH, containing only the pET28 plasmid (control strain) and those of the AB1548 strain complemented with either PA4781 or PA4781_HD-GYP (a truncated version of the protein lacking the REC domain). c-di-GMP levels of the parental <i>E</i>. <i>coli</i> strain (AB472) were used as reference (100%). Data are the mean of at least two independent experiments, each being done in duplicate. (B) PDE activity in soluble cell extracts of BL21(DE3) <i>E</i>. <i>coli</i> strain overexpressing either PA4781 or PA4781_HD-GYP. The control strain (BL21 pET28 in the figure) was analysed after incubation with or without c-di-GMP, in order to evaluate the levels of unreacted c-di-GMP to be compared to the physiological levels in this background. Data are the mean of at least three independent experiments, each being done in duplicate. In (A) and (B) statistical significance with respect to <i>E</i>. <i>coli</i> AB472 or BL21 pET28 with c-di-GMP, respectively, is indicated with one asterisk (p < 0.01).