In S. meliloti, the control of secondary infection is mediated by a bacterial cAMP-cascade involving three receptor-like adenylate cyclases (ACs), CyaD1 (SMc02176), CyaD2 (SMc04307) and CyaK (SMb20776), a cAMP-dependent transcriptional regulator of the Crp family (Green et al., 2014), called Clr (SMc02175), and smc02178, a gene of unknown biochemical function located nearby cyaD1 and clr on the chromosome. The gene discussed is DCLK3; the disease is infection.