Compositional genomes: Prebiotic information transfer in mutually catalytic noncovalent assemblies

Mutually catalytic sets of simple organic molecules have been suggested to be capable of self-replication and rudimentary chemical evolution. Previous models for the behavior of such sets have analyzed the global properties o f short biopolymer ensembles by using graph theory and a mean field approac h. In parallel, experimental studies with the autocatalytic formation of am phiphilic assemblies (e.g., lipid vesicles or micelles) demonstrated self-r eplication properties resembling those of living cells. Combining these app roaches, we analyze here the kinetic behavior of small heterogeneous assemb lies of spontaneously aggregating molecules, of the type that could form re adily under prebiotic conditions. A statistical formalism for mutual rate e nhancement is used to numerically simulate the detailed chemical kinetics w ithin such assemblies, We demonstrate that a straightforward set of assumpt ions about kinetically enhanced recruitment of simple amphiphilic molecules , as well as about the spontaneous growth and splitting of assemblies, resu lts in a complex population behavior. The assemblies manifest a significant degree of homeostasis, resembling the previously predicted quasi-stationar y states of biopolymer ensembles (Dyson, F. J, (1982) J. Mel. Evol. 18, 344 -350). Such emergent catalysis-driven, compositionally biased entities may be viewed as having rudimentary "compositional genomes," Our analysis addre sses the question of how mutually catalytic metabolic networks, devoid of s equence-based biopolymers, could exhibit transfer of chemical information a nd might undergo selection and evolution. This computed behavior may consti tute a demonstration of natural selection in populations of molecules witho ut genetic apparatus, suggesting a pathway from random molecular assemblies to a minimal protocell.