Figure 4

Promoter activities per cell under non-induced (0 mM IPTG) and induced (1 mM IPTG) conditions, characterized using an EYFP reporter construct carried on pPMQAK1 [25]in Escherichia coli NEB5α F’ I^q(New England Biolabs). A. Control promoters. J23101 corresponds to BioBrick BBa_J23101 (iGEM Registry [34]) and is a constitutive control promoter without lac operator (lacO). Ptrc 2O-original is the Ptrc 2O version previously characterized [25] with lacO1 in the proximal position and the symmetric lacO (lacO sym) in the distal position. Ptrc 1O-distal, -core, and-proximal are Ptrc-derived promoters with only one lacO sym at the indicated position. PA1lacO-1 is a previously used promoter with lacO in the core and proximal positions [36]. B. The Ptrc 2O-library. The length of the spacer sequence between the −35 box and the distal lacO sym is indicated on the upper x-axis and the distance between the two lacO sym is indicated on the lower x-axis. Promoter activities per cell are given in fluorescence/absorbance at 595 nm in arbitrary units [AU]. Error bars indicate standard error of the mean (n = 6). The numbers on top of the columns are the induction ratios. na, not available (repressed fluorescence under detection limit). IPTG, Isopropyl β-D-1-thiogalactopyranoside.