Programming Bacteria With Light-Sensors and Applications in Synthetic Biology

Abstract

Photo-receptors are widely present in both prokaryotic and eukaryotic cells, which serves as the foundation of tuning cell behaviors with light. While practices in eukaryotic cells have been relatively established, trials in bacterial cells have only been emerging in the past few years. A number of light sensors have been engineered in bacteria cells and most of them fall into the categories of two-component and one-component systems. Such a sensor toolbox has enabled practices in controlling synthetic circuits at the level of transcription and protein activity which is a major topic in synthetic biology, according to the central dogma. Additionally, engineered light sensors and practices of tuning synthetic circuits have served as a foundation for achieving light based real-time feedback control. Here, we review programming bacteria cells with light, introducing engineered light sensors in bacteria and their applications, including tuning synthetic circuits and achieving feedback controls over microbial cell culture.

Keywords: feedback control; genetic circuits; light-sensors; optogenetics; synthetic biology.

Figure 1

Schematics of two-component and one-component systems. (A) Two component systems consist of a sensor histidine kinase (HK) and a response regulator (RR). Activities of response regulators for transcription are tuned by phosphate signaling upon light illumination. (B) Photo-induced LOV2-Jα dissociation uncages the fused protein in response to blue light, releasing its activity. (C,D) Light-induced dimerization and oligomerization of sensors result in the interaction of the attached proteins. (E) Photo-induced dissociation of Dronpa tetramer releases the protein of interest.

Figure 2

Applications of light sensors in bacteria. (A) EL222 light-controlled bidirectional transcription system activates and represses gene expression via different binding strategies. (B) Split T7RNAP is brought together by Magnets, reconstituting its transcriptional activity. (C) Schematic of microbe-hardware interface and real-time feedback control system. Realtime feedback control is realized by algorithms and hardware. Hardware includes three modules: (1) a cell culture system (2) a real-time quantification system (3) a computer-controlled light-delivery system.