Part of a signaling cascade that regulates curli biosynthesis. The cascade is composed of two cyclic-di-GMP (c-di-GMP) control modules, in which c-di-GMP controlled by the DgcE/PdeH pair (module I) regulates the activity of the DgcM/PdeR pair (module II), which in turn regulates activity of the transcription factor MlrA and expression of the master biofilm regulator csgD (PubMed:23708798). DgcM stimulates activity of MlrA by direct interaction, leading to the transcription of csgD. It also catalyzes the synthesis of c-di-GMP via the condensation of 2 GTP molecules, which contributes to the c-di-GMP pool generated by module I in a positive feedback loop. Production of c-di-GMP contributes to but is not essential for MlrA activation (PubMed:17010156, PubMed:23708798). 2 GTP = cyclic di-3',5'-guanylate + 2 diphosphate Binds 1 Mg(2+) ion per monomer. Activity is inhibited by the phosphodiesterase PdeR. Inhibition is relieved by high cellular c-di-GMP levels. Purine metabolism; 3',5'-cyclic di-GMP biosynthesis. Forms homodimers and homotetramers (PubMed:23708798). Interacts with PdeR and MlrA (PubMed:23708798). Expressed during transition into stationary phase, expression is higher at 28 than 37 degrees Celsius, more highly expressed on plates than in liquid medium. In rich medium DgcM and DosC are the major RpoS-dependent GGDEF-domain containing proteins in the cell. Expression is RpoS and H-NS dependent. Loss of curli fimbriae, decreased biofilm formation, decreased expression of DgcC, a probable diguanylate cyclase and of the curli regulator CsgD.