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. 2017 Sep 11;8:1670. doi: 10.3389/fmicb.2017.01670

Figure 1.

Figure 1

Geometrical model of the bacterial septum and the Z-ring (red) at early (Left) and late (Right) stages of constriction. It assumes that before the onset of division the cell shape is that of a cylinder with two hemispherical caps. The cell radius, R, is defined as the radius of the cylindrical section of the cell enclosed by the cytoplasmic membrane. We assume that R is constant throughout the septation process. During division, the septum consists of two incomplete hemispheres joined at midcell. We define the constriction radius, r, as the radius of the circle joining the two septal incomplete hemispheres. The Z-ring is modeled as a wide ring centered in the septal plane and attached to the cytoplasmic membrane. Its radius, rz, is measured from the middle of its radial width to the long cell axis and its radial width, Δ, is twice the difference between r and rz, Δ = 2(rrz). Our results indicate that for fast growing E. coli cells the radial width of the Z-ring, Δ, grows during septation.