Sensory Perception in Bacterial Cyclic Diguanylate Signal Transduction

Cyclic diguanylate (c-di-GMP) signal transduction systems provide bacteria with the ability to sense changing cell status or environmental conditions and then execute suitable physiological and social behaviors in response. In this review, we provide a comprehensive census of the stimuli and receptors that are linked to the modulation of intracellular c-di-GMP. Emerging evidence indicates that c-di-GMP networks sense light, surfaces, energy, redox potential, respiratory electron acceptors, temperature, and structurally diverse biotic and abiotic chemicals. Bioinformatic analysis of sensory domains in diguanylate cyclases and c-di-GMP-specific phosphodiesterases as well as the receptor complexes associated with them reveals that these functions are linked to a diverse repertoire of protein domain families. We describe the principles of stimulus perception learned from studying these modular sensory devices, illustrate how they are assembled in varied combinations with output domains, and summarize a system for classifying these sensor proteins based on their complexity. Biological information processing via c-di-GMP signal transduction not only is fundamental to bacterial survival in dynamic environments but also is being used to engineer gene expression circuitry and synthetic proteins with a la carte biochemical functionalities.

Automated summary

Cyclic diguanylate (c-di-GMP) signal transduction systems allow bacteria to sense and respond to changing cell status or environmental conditions. This review provides a comprehensive overview of the stimuli and receptors that modulate intracellular c-di-GMP levels. The analysis of sensory domains in diguanylate cyclases and c-di-GMP-specific phosphodiesterases, as well as their associated receptor complexes, reveals a diverse repertoire of protein domain families involved in these functions. The principles of stimulus perception learned from studying these modular sensory devices are described, along with their assembly in various combinations with output domains. Furthermore, a system for classifying these sensor proteins based on their complexity is summarized. Biological information processing via c-di-GMP signal transduction is not only crucial for bacterial survival in dynamic environments, but also holds potential for engineering gene expression circuitry and synthetic proteins with customized biochemical functionalities.