Globin-coupled heme-based oxygen sensor protein displaying diguanylate cyclase (DGC) activity in response to oxygen availability. Thus, catalyzes the synthesis of cyclic diguanylate (c-di-GMP) via the condensation of 2 GTP molecules. Cyclic-di-GMP is a second messenger which controls cell surface-associated traits in bacteria (By similarity). 2 GTP = cyclic di-3',5'-guanylate + 2 diphosphate Binds 1 heme group per subunit. Binds 1 Mg(2+) ion per subunit. Purine metabolism; 3',5'-cyclic di-GMP biosynthesis. Is composed of an N-terminal sensory globin-fold domain that binds heme and oxygen, and a C-terminal GGDEF diguanylate cyclase domain.