Figure 5.

ori- and ter- Focus Distributions in Various Mutants

(A) Percentages of cells in five classes of distributions of ori and ter foci (104–144 cells/genotype). Colors refer to arrows in Figure 4B, showing examples of each class. “Normal” defined per Figure 3 and with ori and ter signal numbers within the range observed in wild-type (WT) cells at the same temperature.

(B) Numbers of ori foci per cell in cells with many ori and a single ter focus at a cell pole (red class). Comparable numbers in dying recA(Ts) ΔruvB ΔuvrD cells and parE(Ts) chromosome-segregation-defective control. Means ± SD.

(C) Numbers of foci in ori-only and ter-only cells in various mutants. In most genotypes, the average numbers were approximately 3±1 (e.g., ori signal for WT at 30°C). Imperfect probe labeling/hybridization and 3-D constraints on cell visualization should yield rare cells with only ori or ter foci. Both dying recA(Ts) ΔruvB ΔuvrD cells (30°C) and parE(Ts) (42°C) had ori-only cells (green class) with significantly more foci than this apparent background, suggesting similar chromosome-segregation defects in these strains. ori-only cells are thought to form from inappropriate septation after failed chromosome segregation. Means ± SD.

(D) Numbers of ori and ter foci per unit of cell length are reduced (proportionately) in ΔruvB ΔuvrD recA(Ts) cells (30°C) and parE(Ts) cells (42°C) during chromosome-segregation failure (yellow-class population of C). This might indicate loss of the coordinate regulation of cell growth and chromosome replication. Blue and red lines, best-fit regressions passing through zero for strains grown at 30°C or 42°C. Means ± SEM. Supplemental Data for strains.