Catalyzes the ATP-dependent phosphorylation of sn-l,2-diacylglycerol (DAG) to phosphatidic acid. a 1,2-diacyl-sn-glycerol + ATP = a 1,2-diacyl-sn-glycero-3-phosphate + ADP + H(+) Belongs to the bacterial diacylglycerol kinase family.