Figure 2. Imbalance of Replication Arms.

(A) Schematic representation of the E. coli chromosome after interreplichore inversion leading to a 20% imbalance (replication arms are 30% and 70% of the total length of the chromosome). The two replication arms are indicated by red arrows, and the replication fork trap is indicated in yellow. The ten Ter sites (from A to J), replication origin oriC, and dif site are indicated.

(B) Colonies of strains carrying chromosomes with various levels of imbalance as indicated (47–53: strain Inter R-L3; 42–58: strain Inter R-L5; 36–64: strain Inter R-NS^left1; 30–70: strain Inter R-NS^left2; 23–77: strain Inter R-NS^left4; and 18–82: strain Inter R-O1). Colonies were obtained in a wt, recA, or recA tus genetic background.

(C) Quantification of the growth defects caused by replication arms imbalance. Strains carrying a chromosome with 3% (47–53), 14% (36–64), or 20% (30–70) of replication arms imbalance described in (B) were grown in serial cocultures with the strain carrying the wt configuration. The ratio of inverted to wt configurations is plotted as a function of the number of generations.

(D) Comparison of microscopic analyses of strains carrying a chromosome with 14% (36–64) or 32% (18–82) of replication arms imbalance described in (B). Colored horizontal bars indicate the percentage of the different types of cells and nucleoids in the wt (noninverted; left) and inverted (right) configurations. Green indicates cells containing one and two nucleoids (1+2 nuc); yellow: cells containing four nucleoids (4 nuc); cyan: cells containing par-like nucleoids (par); red: cells with unsegregated nucleoid (CUN); and pink: anucleate (anuc).