Validation of the dual GFP<i>-luxCDABE</i> reporter system.

<p>(<b>a</b>) Structure of the reporter systems used. In the three cases, the expression of the different reporters is triggered by a <i>lacI^q-Ptrc</i> expression system <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0052000#pone.0052000-Amann1" target="_blank">[28]</a>. Plasmid pGLR2-<i>Ptrc</i> has the dual reporter system, while in pLUX-<i>Ptrc</i>, only the <i>luxCDABE</i> operon is present. Additionally, in the pGFP-<i>Ptrc</i> plasmid, GFP alone is placed under the control of the <i>lacI^q-Ptrc</i> system. (<b>b</b>) and (<b>c</b>) Comparison of reporter performances in response to IPTG. Overnight-grown cells were diluted 1∶20 in fresh M9 minimal media with 1 mM of IPTG. After 4 h of induction, promoter activities were calculated by normalizing the reporter signal (RLU or fluorescence) to the OD₆₀₀. In this sense, promoter activity represents RLU/OD₆₀₀ in (<b>b</b>) and fluorescence/OD₆₀₀ in (<b>c</b>). Vertical bars represent the standard deviation calculated from four technical replicates.