Single cell dynamics of the Lac operon induction

For decades, the lac operon has been used as a model system to study gene expression. Seminal studies on this paradigmatic operon have uncovered the key role of transcription factors and complex regulatory networks in controlling gene expression. More recent work, benefitting from development on single cell imaging techniques, made use of the lac operon to characterize the dynamics of transcription factors and the importance of stochastic processes in gene networks.

In this work, we designed mother machine devices to directly observe the switch-like behaviour of the lac operon at the single cell level. Our experiments enrich available bulk and single cell population measurements by (1) exploring different growth conditions and (2) providing an extra layer of information that can be directly compared with stochastic simulations.

We show that both stochastic irreversible switching and bi-stable behaviour can be observed in microfluidic chambers depending on the growth conditions. Our quantitative measurements are presented considering recent models and simulations.