Diversity Takes Shape: Understanding the Mechanistic and Adaptive Basis of Bacterial Morphology
(A) Phylogeny of the order Caulobacterales generated as described in Fig 1. Schematics and corresponding colors indicate inferred ancestral morphologies and their subsequent inheritance. Black branches indicate rod-shape, nonappendaged morphology, including several apparent prostheca loss events. Scale bar indicates 0.1 amino acid substitutions per site. (B) Transmission electron micrographs of members of the Caulobacterales, highlighting disparate prosthecate morphologies. For each morphology, a brief description and the name of one representative species is provided, followed by the image source in parentheses. 1. Bilateral prosthecae, Asticcacaulis biprosthecum (Chao Jiang, Stanford University). 2. Subpolar prostheca, Asticcacaulis excentricus (Chao Jiang, Stanford University). 3. Polar prostheca, Caulobacter crescentus (Paul Caccamo, Indiana University). 4. Polar prostheca, Maricaulis maris (Patrick Viollier, University of Geneva). 5. Short polar prostheca, Brevundimonas subvibriodes (Brynn Heckel, Indiana University); note other members of this genus display a much longer prostheca. 6. Polar prostheca through which budding reproduction occurs, Hirschia baltica (Paul Caccamo, Indiana University). Magnification varies between micrographs. All images are reproduced with permission.