Oscillation of DnaA-YFPsw in E. coli.

Fluorescence microscopy images of E. coli cells, A) expressing DnaA-YFPsw during exponential growth, B) 60 min after the addition of 200 μg/ml rifampicin, C) B. subtilis cells expressing TetR-YFP binding to a tetO array near oriC. Fluorescence intensities of two areas, each containing one fluorescence signal, were measured and normalized to the total fluorescence intensity of the cell. Intensities of both areas were plotted over time. Area 1 (black) and area 2 (white). Image sequences displaying the oscillation of DnaA-YFPsw (A–B) and the static TetR-YFP (C) are shown. White lines, cell borders; scale bars, 2 μm; white dashed lines, cell outlines; black open circle, area 1; green open circle; area 2. To visualize the correlation between the two measured areas they were plotted against each other (D–F). Correlation coefficients (r) were determined.