Diversity Takes Shape: Understanding the Mechanistic and Adaptive Basis of Bacterial Morphology
(A–C) In prosthecate Alphaproteobacteria, simply repositioning zonal PG synthesis machinery (shown in green) can generate polar (Caulobacter crescentus, A), subpolar (Asticcacaulis excentricus, B), or bilateral (Asticcacaulis biprosthecum, C) prosthecate phenotypes. (D) Similar repositioning of the PG growth zone yields a branching phenotype in Streptomyces coelicolor, which grows from the cell poles. (E) The intermediate filament-like protein crescentin (shown in cyan) of C. crescentus constrains PG synthesis to generate cell wall curvature. (F) When cells filament, this constraint results in long helical shapes. (G) The periplasmic flagella of Borrelia burgdorferi directly deform the cell body into a planar wave shape. Note that the scale of the periplasmic space, relative to the cell membranes, has been modified to highlight this arrangement. For simplicity, details of the periplasmic compartment are shown only for panel G.