Optogenetic control of bacterial engineered metabolism: An alternative to IPTG induction of protein expression

Abstract

Optogenetics is an emerging technology involving the control of cells using light by utilizing photosensitive proteins that induce downstream effects. This technology has potential applications in microbial metabolic engineering, in which microbes are genetically modified to convert low-value materials, such as plant biomass and industrial waste, into high-value complex compounds, such as pharmaceuticals. One important strategy for optimizing a metabolic pathway is to regulate the level and timing of gene expression, as engineered pathways often divert resources away from necessary cellular processes. In this project, we build a modular optogenetic switch to flexibly control gene expression in Escherichia coli bacteria, a commonly used host species for metabolic engineering. This switch turns off expression of a target gene under blue light, and turns it on in the dark, with a 21-fold dynamic range. It provides a convenient optogenetic alternative to the traditional chemically regulated method for controlling target gene expression (using IPTG, Isopropyl β-D-1-thiogalactopyranoside), by instead using light to regulate the amount of LacI transcriptional repressor present in the cell. This optogenetic switch provides an invaluable tool that will make light-based control far more widely applicable to metabolic engineering.