Initiation of multiple rounds of replication uncouples the final stages of chromosome segregation from cell division.

(A) Rate of dif-cassette (left panel) and recA-dependency (right panel) of dif-cassette excision measured over 16 h in fast (LB) and slow (M9) growing E. coli cells. Mean of 5 independent experiments. *: p <0.01 (t-test with a Two-tailed distribution). (B) Consensus images summarising the cell cycle choreography of the ydeV fluorescence marker (upper panels, GFP) and the cell shape (lower panels, BF) in fast (left panels) and slow (right panels) growing E. coli cells. Only cells that were followed from birth to division were taken into consideration. At each time point, the maximal and minimal intensities of the projections were set to 1 and 0, respectively. We created images describing the evolution of the fluorescence and cell shape in the cell cycle by plotting the different projections of individual cells as a function of time using a jet colour code. In the heat maps, black corresponds to the lowest and dark red to the highest intensities. In the GFP maps the red areas indicate the presence of the ydeV marker, in the BF maps the green line indicates the Septa appearance. Individual fluorescence and cell shape images were compiled into consensus images summarising the results. Y-axis: position along the cell length. X-axis: cell cycle. GT: generation time; n: number of complete cell cycles that were analysed; op: old pole; np: new pole. 0: birth; 1: division. (C) Frequency of cells displaying a single spot (blue line), two spots (red line) and 3 or more spots (black line) as a function of the time before or after septation was detected. The Y-axis serves for both the cell type frequency lines and to the relative spot positions, with 0 indicating 0% frequency or the old pole position and 1 indicating 100% frequency or the new pole position. Left panels: M9-Rich; right panels: M9. The percentage of cells with a single ydeV spot at the time when septation was detected is indicated in blue with the number of observed cells (n) between parentheses. The percentage of new ydeV duplication events 0% per min and 4.3% per min represented at the time when septation was detected is indicated in red. GT: generation time.