Hypothesis: Hyperstructures regulate bacterial structure and the cell cycle

A myriad different constituents or elements (genes, proteins, lipids, ions, small molecules etc.) participate in numerous physico-chemical processes t o create bacteria that can adapt to their environments to survive, grow and , via the cell cycle, reproduce. We explore the possibility that it is too difficult to explain cell cycle progression in terms of these elements and that an intermediate level of explanation is needed. This level is that of hyperstructures. A hyperstructure is large, has usually one particular func tion, and contains many elements. Non-equilibrium, or even dissipative, hyp erstructures that, for example, assemble to transport and metabolize nutrie nts may comprise membrane domains of transporters plus cytoplasmic metabolo ns plus the genes that encode the hyperstructure's enzymes. The processes i nvolved in the putative formation of hyperstructures include: metabolite-in duced changes to protein affinities that result in metabolon formation, lip id-organizing forces that result in lateral and transverse asymmetries, pos t-translational modifications, equilibration of water structures that may a lter distributions of other molecules, transertion, ion currents, emission of electromagnetic radiation and long range mechanical vibrations. Equilibr ium hyperstructures may also exist such as topological arrays of DNA in the form of cholesteric liquid crystals. We present here the beginning of a pi cture of the bacterial cell in which hyperstructures form to maximize effic iency and in which the properties of hyperstructures drive the cell cycle. (C) 1999 Societe francaise de biochimie et biologie moleculaire/Editions sc ientifiques et medicales Elsevier SAS.