FIGURE 2.

Growth modes in rod-shaped bacteria. Several growth modes with the regions of active peptidoglycan synthesis are schematized. Colors indicate regions of active peptidoglycan synthesis. (A) Lateral elongation is well-studied in E. coli, B. subtilis, and C. crescentus, and often assumed for many rod-shaped bacteria. (B) A majority of bacterial families divide in a FtsZ-dependent manner. Notable exceptions are members of the PVC (Planctomycetes, Verrucomicrobia, and Chlamydiae) superfamily. (C) Polar elongation is characteristic of Actinobacteria, where it is bipolar. It has recently been demonstrated in Rhizobiales (Brown et al., 2012) where it is unipolar. (D) Budding occurs both at the ends of stalks and off the cell body in Alphaproteobacteria. (E) Stalks are wide-spread in Alphaproteobacteria. While the exact mechanism for growth may differ among families, all depend on zonal growth of the peptidoglycan at the cell-stalk junction. (F) Some species exhibit medial (pre-septal) growth, which appears to be peptidoglycan synthesis near the division plane before full assembly of the Z-ring.