Abstract
Cyclic di-guanosine monophosphate (c-di-GMP) is a ubiquitous second messenger that regulates distinct aspects of bacterial physiology. It is synthesized by diguanylate cyclases (DGCs) and hydrolyzed by phosphodiesterases (PDEs). To date, the activities of DGC and PDE are commonly assessed by phenotypic assays, mass spectrometry analysis of intracellular c-di-GMP concentration, or riboswitch-based fluorescent biosensors. However, some of these methods require cutting-edge equipment, which might not be available in every laboratory. Here, we report a new simple, convenient and cost-effective system to assess the function of DGCs and PDEs in E. coli. This system utilizes the high specificity of a riboswitch to c-di-GMP and its ability to regulate the expression of a downstream β-galactosidase reporter gene in response to c-di-GMP concentrations. In this protocol, we delineate the construction of this system and its use to assess the activity of DGC and PDE enzymes.