Catalyzes the phosphorylation of undecaprenol in vitro, which is probably the physiological substrate. Exhibits no detectable activity against other substrates such as monoacylglycerol, ceramide, or diacylglycerol (DAG). Appears indispensable for the maintenance of spore stability and viability in B.subtilis. ATP + di-trans,octa-cis-undecaprenol = ADP + di-trans,octa-cis-undecaprenyl phosphate + H(+) Localized in both lateral and septal membranes. Mainly expressed during the vegetative phase of growth. Cells lacking this gene exhibit an abnormal cortex structure in mutant endospores 6 hours after the onset of sporulation, an indication of cortex degeneration. In addition, they display a significant decrease in the dipicolinic acid content of mutant spores. Belongs to the bacterial diacylglycerol kinase family. Was originally thought to be a diacylglycerol kinase. Extended N-terminus.