Dynamic Executors of Bacterial Signals: Functional Versatility and Regulatory Networks of c-di-GMP Effectors

Cyclic di-GMP (c-di-GMP), a universal second messenger in bacteria, orchestrates a wide array of essential life processes. Its intracellular dynamics are meticulously regulated by diguanylate cyclases (DGCs) and phosphodiesterases (PDEs), ensuring precise spatiotemporal control. The functional output of c-di-GMP signaling hinges on effector proteins—molecular decoders that translate c-di-GMP signals into specific cellular responses. This review systematically examines diverse classes of c-di-GMP effectors, using several representative bacterial species as model systems, to dissect their structural and mechanistic diversity. Particular emphasis is placed on their pivotal roles in bacterial pathogenicity, antibiotic tolerance, and host–pathogen interactions, offering fresh insights into the regulatory mechanisms underlying c-di-GMP signaling.