TY - JOUR T1 - Cycling Physicochemical Gradients as ‘Evolutionary Drivers’: From Complex Matter to Complex Living States JF - bioRxiv DO - 10.1101/000786 SP - 000786 AU - Jan Spitzer Y1 - 2013/01/01 UR - http://biorxiv.org/content/early/2013/11/20/000786.abstract N2 - HighlightsBiological complexity cannot be reduced to chemistry and physicsComplex living states are: multicomponent, multiphase, ‘crowded’, and re-emergentLiving states arise naturally only by the action of cycling physicochemical gradientsBacterial cells can be modeled as viscoelastic capacitors with sol-gel transitionsEvolving living states can be investigated via ‘biotic soup’ experimentationDarwinian evolution arises from the process errors of the cell cycleSynthetic biology heralds the transition from unintentional Darwinian evolution to intentional anthropic evolutionAbstract Within the overlap of physics, chemistry and biology, complex matter becomes ‘more deeply’ understood when high level mathematics converts regularities of experimental data into scientific laws, theories, and models (Krakauer et al., 2011. The challenges and scope of theoretical biology. J. Theoret. Biol. 276: 269–276). The simplest kinds of complex biological matter are bacterial cells; they appear complex–from a physicochemical standpoint–because they are multicomponent, multiphase, biomacromolecularly crowded, and re-emergent; the property of re-emergence differentiates biological matter from complex chemical and physical matter.Bacterial cells cannot self-reassemble spontaneously from their biomolecules and biomacromolecules (via non-covalent molecular forces) without the action of external ‘drivers’; on Earth, such drivers have been diurnal (cycling) physicochemical gradients, i.e. temperature, water activity, etc. brought about by solar radiation striking the Earth’s rotating surface. About 3.5 billion years ago, these cycling gradients drove complex chemical ‘prebiotic soups’ toward progenotic living states from which extant bacteria evolved (Spitzer and Poolman, 2009; The role of biomacromolecular crowding, ionic strength and physicochemical gradients in the complexities of life’s emergence. Microbiol. Mol. Biol. Revs. 73:371–388). Thus there is historical non-equilibrium continuity between complex ‘dead’ chemical matter and complex living states of bacterial cells. This historical continuity becomes accessible to present-day experimentation, when cycling physicochemical gradients act on ‘dead’ biomacromolecules obtained from (suitably) killed bacterial populations – on a ‘biotic soup’ of chemicals (Harold, 2005, Molecules into cells: specifying spatial architecture. Microbiol. Mol. Biol. Rev. 69:544–564). The making of biotic soups and recovering living states from them is briefly discussed in terms of novel concepts and experimental possibilities.In principle, emergent living states contingently arise and evolve when cycling physicochemical gradients continuously act on complex chemical mass; once living states become dynamically stabilized, the inevitable process errors of ‘primitive’ cell cycles become the roots of Darwinian evolution. ER -