Synthetic symbiosis combining plasmid displacement enables rapid construction of phenotype-stable strains

Plasmid-based microbial systems have been a major workhorse for chemical and pharmaceutical production. The biosafety issues and elevated industrial cost of antibiotic usage have led to the development of alternative strategies for plasmid selection and maintenance. Such strategies, including auxotrophy complementation, post-segregational killing, operator-repressor and RNA-based interactions often require extensive engineering of various elements and may result in extra metabolic burden in the cells. Herein, we report a design of synthetic symbiosis combining plasmid displacement to construct a phenotype-stable microbial system. By sequestrating an endogenous essential gene folP, cells obtained long-term plasmid maintenance with minimum cost. The phenotype performance was also inherited for up to 80 generations demonstrated by the production of salicylic acid in Escherichia coli. Meanwhile, the temperature-induced curing method of the intermediate plasmids enables rapid engineering. This design can lead to broad applications as a reliable and convenient plasmid-based expression system.