title: Filamentation as primitive growth mode?
abstract: Osmotic pressure influences cellular shape. In a growing cell, chemical reactions and dilution induce changes in osmolarity, which in turn influence the cellular shape. Using a protocell model relying upon random conservative chemical reaction networks with arbitrary stoichiometry, we find that when the membrane is so flexible that its shape adjusts itself quasi-instantaneously to balance the osmotic pressure, the protocell either grows filamentous or fails to grow. This behavior is consistent with a mathematical proof. This suggests that filamentation may be a primitive growth mode resulting from the simple physical property of balanced osmotic pressure. We also find that growth is favored if some chemical species are only present inside the protocell, but not in the outside growth medium. Such an insulation requires specific chemical schemes. Modern evolved cells such as E. coli meet these requirements through active transport mechanisms such as the phosphotransferase system.
authors.affiliation: Laboratoire d'Informatique (LIX), École Polytechnique, F-91128 Palaiseau Cedex, France. Laboratoire Matière et Systèmes Complexes, UMR7057 CNRS, Université Paris Diderot, F-75205 Paris Cedex 13, France.
authors.forename: Erwan
authors.initials: E
authors.lastname: Bigan
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Steyaert
authors.forename: Stéphane
authors.initials: S
authors.lastname: Douady
mesh_terms: D002453:Cell Cycle; D002462:Cell Membrane / Q000502:physiology*; D004926:Escherichia coli / Q000254:growth & development*; D008954:Models, Biological; D009997:Osmotic Pressure