CrvA and CrvB form a curvature-inducing module sufficient to induce cell shape complexity in Gram-negative bacteria

Bacterial species have diverse cell shapes that enable motility,
colonization, and virulence. The cell wall defines bacterial shape and is
primarily built by two cytoskeleton-guided synthesis machines, the
elongasome and the divisome. However, the mechanisms producing complex
shapes, like the curved-rod shape of Vibrio cholerae, are incompletely
defined. Previous studies have reported that species-specific regulation
of cytoskeleton-guided machines enables formation of complex bacterial
shapes such as cell curvature and cellular appendages. In contrast, we
report that CrvA and CrvB are sufficient to induce complex cell shape
autonomously of the cytoskeleton in V. cholerae. The autonomy of the CrvAB
module also enables it to induce curvature in the Gram-negative species
Escherichia coli, Pseudomonas aeruginosa, Caulobacter crescentus, and
Agrobacterium tumefaciens. Using inducible gene expression, quantitative
microscopy, and biochemistry we show that CrvA and CrvB circumvent the
need for patterning via cytoskeletal elements by regulating each other to
form an asymmetrically-localized, periplasmic structure that directly
binds to the cell wall. The assembly and disassembly of this periplasmic
structure enables dynamic changes in cell shape. Bioinformatics indicate
that CrvA and CrvB may have diverged from a single ancestral hybrid
protein. Using fusion experiments in V. cholerae, we find that a synthetic
CrvA/B hybrid protein is sufficient to induce curvature on its own, but
that expression of two distinct proteins, CrvA and CrvB, promotes more
rapid curvature induction. We conclude that morphological complexity can
arise independently of cell shape specification by the core
cytoskeleton-guided synthesis machines. The original raw data files for
this project are primarily microscopy data. The files are organized into a
directory structure that reflects the experiments that go into each figure
and subfigure panel. Included in the README.txt are (I) a description of
the file types and (II) a comma separated table documenting the folder
structure and how many of each file type is in each folder.