Living cells employ small diffusible molecules, so-called second messengers, to signal environmental cues from sensory proteins to cellular receptors. Only recently, it has become apparent that bacteria utilize the cyclic dinucleotide c-di-GMP as a ubiquitous second messenger to switch between rapidly growing single cells and a quiescent life style, called biofilm. In pathogenic bacteria, this switch is often accompanied by the transition from an acute to a chronic phase of infection. This makes c-di-GMP signal transduction an attractive target for novel antibiotics that interfere with bacterial persistence. The cellular concentration of c-di-GMP is the result of the opposing activities of diguanylate cyclases that synthesize c-di-GMP from two GTP molecules, and phosphodiesterases that degrade the compound. These two key enzymatic activities regulate c-di-GMP and thus the state of the various c-di-GMP receptors and their associated activities within the cell.

To uncover the molecular mechanisms of the c-di-GMP signaling network, this Sinergia project aims at combining in vivo studies with pathogenic and non-pathogenic bacterial model systems with the analysis of the isolated and purified proteins of the network. This involves their enzymatic and biophysical characterization, 3D-structure determination by X-ray crystallography and the study of their dynamic properties by fluorescence energy transfer measurements. Furthermore, the vast amount of bioinformatic data available will be exploited for structure prediction and the identification of yet unrecognized members of the network. The results will further our general knowledge about c-di-GMP mediated cell signaling and behavior and contribute important information towards the successful control of chronic infections by animal and human pathogens.