Many members of the alphaproteobacterial order Rhizobiales are able to establish a nitrogen fixing symbiosis with leguminous host plants. These bacteria possess an exceptional high number of mononucleotide cyclases. The genome of Sinorhizobium meliloti, the microsymbiont of Medicago, Melilotus and Trigonella plants, encodes 28 putative class III adenylate- and guanylate cyclases (AC/GC), seven potential cNMP phosphodiesterases and ten CRP-like proteins potentially binding cNMPs. This high number of cAMP-/cGMP-related proteins suggests their functional diversification.

In the project, we aim at exploring the catalytic activities of mononucleotide cyclases, as well as sensory inputs and biological roles of cNMP-signaling in S. meliloti.