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Abstract

Biosensors are engineered devices built from gene regulatory elements involved in the control of cellular pathways in response to metabolite inputs and physical conditions. The most common sensors in living cells are small molecule-responsive allosteric transcription factors that sense concentrations of metabolites and regulate the expression of operons, especially in prokaryotes. These regulatory elements and their effector metabolites can be used in the discovery of enzymes and metabolic pathways. Nowadays, there are emerging sophisticated methodologies to enable high-throughput screening toward the discovery of novel enzyme functions hidden in environmental metagenomes. Microbial biosensors have also attracted the attention of metabolic and enzyme engineers as a tool to monitor metabolites in screening and selection, as well as in the engineering of dynamic regulation of metabolic pathways. We start with an introduction of the common types of microbial biosensors, transcription factors and riboswitches, and their applications in metabolic engineering, and subsequently focus on protocols for the characterization of transcription factors and the elements they interact with. This chapter aims to give an overview of current methods and applications regarding the utilization of biosensors for both discovery and engineering approaches. © 2021 Elsevier Inc. All rights reserved.