title: What properties of life are universal? Substance-free, scale-free life.
abstract: One approach to answering the question of what properties of life are universal is to try to answer the question of what are the essential properties of biology's best understood model organism, Escherichia coli. One of these properties is competitive coherence whereby E. coli reconciles the generation of a coherent cell state with the generation of a coherent sequence of cell states. The second property is differentiation which occurs ineluctably when E. coli divides. The third property is dualism which is how E. coli navigates between the two main attractors of phenotypes - survival and growth - which are based on quasi-equilibrium and non-equilibrium structures, respectively. The fourth property is complementarity: the interactions between the molecules and macromolecules that constitute E. coli protect them from degradation and confer new properties. The fifth property is multi-scale existence: E. coli exists at levels extending from the bacterium to the global super-organism. The sixth property is maintenance of connectivity; growth alters connectivity and, in the case of E. coli, alters the phenotype. The seventh property is the combination of intensity sensing (the constituents can work no harder) and quantity sensing (too much unused material has been made); this combination is used by E. coli to drive its cell cycle and thereby generate an environmentally adapted population of cells. The eighth property is subjective experience which exists even at the level of a single E. coli but which only becomes important at higher levels of organisation. I propose that the search for life at other times and in other places be based on the above eight universal properties and be independent of both particular substances and spatio-temporal scales.
authors: Theoretical Biology Unit, Laboratory of Microbiology Signals and Microenvironment, EA 4321, Mont Saint Aignan, 76821, France, victor.norris@univ-rouen.fr.
authors: Vic
authors: V
authors: Norris
mesh_terms: D002451:Cell Compartmentation; D002455:Cell Division / Q000502:physiology; D004734:Energy Metabolism / Q000502:physiology; D004926:Escherichia coli / Q000254:growth & development* / Q000378:metabolism* / Q000648:ultrastructure; D019369:Life; D050296:Microbial Viability; D008954:Models, Biological; D015398:Signal Transduction