Control of competence regulator ComK, YlbF/YmcAYlbF Is a family of short Gram-positive and archaeal proteins that includes both YlbF and YmcA which may interact synergistically. The family is necessary for correct biofilm formation, as null mutants of ymcA and ylbF fail to form pellicles at air-liquid interfaces and grow on solid media as smooth, undifferentiated colonies. During development, YmcA, YlbF and YaaT, family PSPI, pfam04468, interact directly with one another forming a stable ternary complex, in vitro. All three proteins are required for competence, sporulation and the formation of biofilms. The YmcA-YlbF-YaaT complex affects the phosphotransfer between Spo0F and Spo0B, thus accelerating the production of Spo0A~P. The three processes of biofilm formation, mature spore formation and competence all require the active, phosphorylated form of Spo0A, as Spo0A-P.