The Quiescent-Cell Expression System for Protein Synthesis in Escherichia coli

The quiescent-cell expression system is a radical alternative to conventional fermentation for protein overproduction in Escherichia coli. It is dependent on the controlled overexpression of a small RNA called Rcd in hns mutant strains to generate nongrowing, quiescent cells which are not nutrient limited. Quiescent cells no longer produce biomass and have their metabolic resources channelled toward the expression of plasmid-based genes. The biosynthetic capacity of the system is demonstrated by its ability to express chloramphenicol acetyltransferase to more than 40% of total cell protein. Quiescent cells may provide an ideal environment for the expression of toxic as well as benign proteins.