Synthetic Networks: Oscillators and Toggle Switches for Escherichia coli

Abstract

Bacterial synthetic gene networks are constructed by manipulating the regulation of genes inside a cell, with the purpose of eliciting novel regulatory behaviors. The methods for manipulating genes and gene regulation in E. coli are well established, making it the preferred host for basic studies of synthetic networks. We focus our work on constructing two kinds of synthetic gene networks: toggle switches (bistable systems) and oscillators. Toggle switches are capable of exhibiting two stable steady states of gene expression (OFF and ON) without stable intermediate states; the steady state reached by the system depends on the previous history of the system. Biological oscillators exhibit regular cycles in gene expression around an unstable steady state. Studying these two kinds of synthetic networks helps advance our understanding of natural bistable systems and oscillators, such as the circadian oscillators controlling gene expression in many types of cells, and the genetic systems controlling the cell cycle and differentiation in metazoans.