The evolution of bacterial shape complexity by a curvature-inducing module

Bacteria can achieve a staggering diversity of cell shapes that promote critical functions like growth, motility, and virulence 1-4 . Previous studies suggested that bacteria establish complex shapes by co-opting the core machineries essential for elongation and division 5,6 . In contrast, we discovered a two-protein module, CrvAB, that can curve bacteria autonomously of the major elongation and division machinery by forming a dynamic, asymmetrically-localized structure in the periplasm. CrvAB is essential for curvature in its native species, Vibrio cholerae , and is sufficient to curve multiple heterologous species spanning 2.5 billion years of evolution. Thus, modular shape determinants can promote the evolution of morphological complexity independently of existing cell shape regulation.