Continuous directed evolution for strain and protein engineering.

Continuous directed evolution is the 'while loop' of synthetic biology, autonomous cycles of mutation, selection, and self-replication that can lead to the rapid development of industrially relevant organisms, pathways, or molecules. Although this engineering strategy requires particular mutagenesis methods and well-defined selections, recent advances have facilitated its implementation. Control over selection pressure has been augmented by novel cost-effective continuous culturing devices with open source designs. New in vivo targeted mutagenesis methods have enabled continuous directed protein evolution in various organisms. Furthermore, advances in automation have enabled rational, semi-continuous directed evolution strategies that may yield fewer artefacts or parasites. Overall, continuous directed evolution is persistently demonstrating its capacity to rapidly generate biotechnologically valuable strains and proteins.