Understanding the shapes of bacteria just got more complicated

The paper by Briegel et al. in this issue of Molecular Microbiology uses advanced cryo-transmission electron microscopy (cryoTEM) techniques to reveal four separate locations of cytoplasmic filament bundles in Caulobacter crescentus. Intuitively, these filaments should be rather rigid protein structures and composed of previously identified shape-forming proteins, such as crescentin or MreB. Yet, deletion mutants lacking these proteins still possessed filaments and still possessed wild-type morphology. These results suggest that a complex combination of protein structures, including those of crescentin, MreB and these newly identified bundles, in combination with the cell envelope help maintain the complicated shape of C. crescentus. Other bacteria might have similar architectural proteins to assist in maintaining the cell contours during growth and division.