Dynamic Tuning of Genetic Circuit Gain via Controllable Plasmid Copy Number

Plasmid copy number directly influences gene expression strength in synthetic genetic circuits and serves as a tunable parameter for adjusting circuit gain and output levels. Building upon recent progress in copy number control, this report presents a genetic circuit that enables dynamic regulation of circuit gain through the regulation of plasmid copy numbers. To illustrate the underlying concept, we first developed a mathematical model describing the relationship between plasmid copy number and circuit gain and simulated the circuit dynamics to examine how gain responds to copy number changes. We then constructed the circuit and experimentally confirmed that plasmid copy number, i.e., circuit gain, can be externally controlled in E. coli. In particular, we demonstrate communication-based gain control using AHL-mediated quorum sensing from co-cultured cells. These results support the feasibility of plasmid copy number control as a practical and predictable strategy for tuning synthetic gene circuit behavior.