<i>mreB</i> is a competence-regulated gene.

<p>A. Partial map of the <i>mreB</i> operon. The three first genes of the operon, <i>maf</i>, <i>radC</i> and <i>mreB</i> are displayed. The three promoter’s upstream <i>mreB</i> (P1, P2 and P3) are represented by black flags. The two black boxes in front of the operon indicate the ComK binding sites that allow competence-specific over-expression of the operon [<a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1005299#pgen.1005299.ref012" target="_blank">12</a>]. The three colored double-headed arrows delimit the fragments used in the luciferase assay to characterize the expression coming from each promoter. P_{<i>mreB123</i>} (in red, strain NC91) contains the three promoters and the ComK boxes, P_{<i>mreB23</i>} (in blue, NC92) contains promoters P2 and P3, and P_<i>mreB3</i> (in green, NC93) only contains the last promoter in front of <i>mreB</i>, P3. B. Transcription profiles of strains expressing P_{<i>mreB123</i>}<i>-luc</i> (in red, NC91), P_{<i>mreB23</i>}<i>-luc</i> (in blue, NC92) or P_<i>mreB3</i><i>-luc</i> (in green, NC93) in a <i>comK</i>+ background during growth in competence medium at 37°C. Transcription rates are presented as the evolution of relative luminescence units corrected for OD (RLU/OD, left y-axis). As a reference, the NC91 growth curve (in black) is represented (OD_<i>600nm</i>, right y-axis). The black arrows denote time points (in hours) relative to the beginning of competence (T_<i>0</i>). The three cultures grew almost identically (see <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1005299#pgen.1005299.s001" target="_blank">S1A Fig</a>) The inset on the top right corner shows the evolution of the ratio between the expression detected from P_{<i>mreB123</i>} and P_<i>mreB3</i>. C. Same as B except that transcription profiles were measured in a <i>comK</i> mutant background (in red, strain NC146; in blue, NC147; in green, NC148). As a reference, the NC146 growth curve (in black) is represented (OD_<i>600nm</i>, right y-axis). The three cultures grew almost identically (see <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1005299#pgen.1005299.s001" target="_blank">S1B Fig</a>). The inset on the top right corner shows the evolution of the ratio between the expression detected from P_{<i>mreB123</i>} and P_<i>mreB3</i> during time in the absence of <i>comK</i>.