Nucleotide second messengers are key components of the signal transduction networks that link sensory input with the regulatory responses of all living cells. Despite having provided early textbook examples such as cAMP and ppGpp, the astonishing diversity, mechanistic complexity and pervasive roles of bacterial second messenger signaling have become apparent only recently. This progress has been triggered by the discovery of the ubiquitous cyclic dinucleotide c-di-GMP, which controls bacterial biofilm formation, cell cycle progression, development and virulence. Research on c-di-GMP has led to entirely new concepts of bacterial second messenger signaling and has sparked intense interest in additional more recently identified second messengers such as c-di-AMP and c-GMP-AMP.

This Priority Programme represents the first systematic and comprehensive strategy ever to understand all fundamental aspects of nucleotide-based second messenger signaling in bacteria at the molecular level.