Figure 2
Characterization of AI-regulated gene activity in V. harveyi strains containing promoter:: gfp reporter fusions. V. harveyi strains containing P luxC ::gfp (A, B) and P vhp ::gfp (C, D) reporter fusions were grown to the mid-exponential growth phase (OD600 = 0.2), and single cell analysis was performed. 450 (P luxC ::gfp) and 300 (P vhp ::gfp) cells were individually analyzed using ImageJ. In panels B and D, fluorescence and bioluminescence levels (normalized for cell size and expressed in arbitrary units) are plotted for individual cells bearing the reporter fusions indicated. The correlation coefficient r and the p-value are indicated. A regression line could be drawn only for strain P luxC ::gfp (red). Panels A and C show phase-contrast (left), bioluminescence (middle) and fluorescence (right) views of cells expressing promoter::gfp fusions for luxC and vhp, respectively. The images in each row show the same field of view. Note the tight correlation between luminescence and luxC reporter expression in panel A. White arrows indicate two cells displaying signals of equal intensity in the bioluminescence and fluorescence channels. In panel C red arrows point to cells that exhibit high bioluminescence and low fluorescence or vice versa. Scale bar = 2.5 μm.