Catalyzes the phosphorylation of undecaprenol, which is probably the primary physiological substrate. Is also able to phosphorylate diacylglycerol, albeit with very low efficiency. May play a role in adaptability to environmental stress conditions such as acid tolerance, elevated temperatures and high osmolarity. ATP + di-trans,octa-cis-undecaprenol = ADP + di-trans,octa-cis-undecaprenyl phosphate + H(+) Cells lacking this gene display defective growth at low pH, elevated temperatures, and high osmolarity. Moreover, they exhibit a significant reduction in the transcription level of mutA and a defect in production of the lantibiotic mutacin II. They also show reduced resistance to bacitracin. Belongs to the bacterial diacylglycerol kinase family. It is uncertain whether Met-1 or Met-3 is the initiator.