Member of the two-component regulatory system DegS/DegU, which plays an important role in the transition growth phase. Involved in the control of expression of different cellular functions, including production of degradative enzymes such as the neutral and alkaline proteases, flagellum formation, biofilm formation, and competence for DNA uptake. Positively or negatively regulates expression of many different genes. The phosphorylated form is required for synthesis of degradative enzymes, flagellum formation and biofilm formation. The unphosphorylated form is required for expression of genetic competence, via induction of comK. Phosphorylated and unphosphorylated forms are both active and have different functions. A low concentration of phospho-DegU is sufficient to activate transcription of flagellar genes, but a higher concentration of phospho-DegU is required for transcription of other genes. Phosphorylated DegU is stabilized by DegR. Phosphorylated DegU activates its own expression. The N-terminal region acts as an inhibitor, whereas the C-terminal region carries enhancing activity. Phosphorylated and dephosphorylated by DegS.