Relative expression ratio of RNR genes in biofilm <i>versus</i> planktonic cells.

<p>The expression level of the indicated genes was measured in cDNA samples derived from 10- and 55-h old <i>E. coli</i> MG1655 biofilms grown at 37°C in PVC plates. For each gene the relative expression was defined as the level in cells from biofilm compared to those from planktonic cells. The 16S rRNA sequence was used as an internal standard. Error bars represent the SD from n = 3 independent replicates.