Bacterial cytoskeleton suprastructures and their physical origin.

Bacterial cytoskeletal filamentous proteins, like their eukaryotic counterparts, are key regulators and central organizers of many cellular processes including morphogenesis, cell division, DNA segregation and movement. Such filaments often organize themselves into complex structures within the prokaryotic cell, driven by molecular crowding and cation association, to form bundles (ParM), rings, toroids and helical spirals (FtsZ) or interwoven sheets (MreB). The formation of complex structures is essential for bacterial cytoskeleton function. Here, we highlight the suprastructures of the prokaryotic cytoskeleton that have been observed by high resolution in vitro electron microscopy and set them in perspective with in vivo observations. We discuss the underlying physical principles that lead to complex structure formation.