Selection for Photocatalytic Function through Darwinian Evolution of Synthetic Self-Replicators

The onset of Darwinian evolution represents a key step in the transition of chemical systems into living ones. Here, we show the emergence of Darwinian evolution in two systems of self-replicating molecules, where natural selection favors replicator mutants best capable of catalyzing the production of the precursors required for their own replication. Such selection for protometabolic activity was observed in a system where trimer and hexamer replicators compete for common resources, as well as in a system of different hexamer replicator mutants. An out-of-equilibrium replication-destruction regime was implemented in a flow reactor, where replication from continuously supplied dithiol building blocks needs to keep up with “destruction” by outflow. Selection occurred based on the ability of the mutants to activate a cofactor that photocatalytically produces singlet oxygen which, in turn, enhances the rate by which dithiol building blocks are converted into disulfide-based replicator precursors. Selection was based on a functional trait (catalytic activity) opening up Darwinian evolution as a tool for catalyst development. This work functionally integrates self-replication with protometabolism and Darwinian evolution and marks a further advance in the de-novo synthesis of life.