Functions as a (p)ppGpp synthase. In eubacteria ppGpp (guanosine 3'-diphosphate 5'-diphosphate) is a mediator of the stringent response that coordinates a variety of cellular activities in response to changes in nutritional abundance. Plays a role in adaptation of Brucella to its intracellular host environment. ATP + GTP = AMP + guanosine 3'-diphosphate 5'-triphosphate Cells show morphological abnormalities such as branching and swelling forms. It does not grow in RPMI-1640 with or without 10% FBS. It shows decreased growth until 48 hours in RPMI-1640 and stationary growth until 48 hours in RPMI-1640 with 10% FBS. It has the same ability as the wild-type to internalize at 0 minute but a lower rate of internalization at 30 minutes. It shows a lower rate of intracellular replication within macrophages than the wild-type. Its adherence is four times higher than that of the wild-type. It shows lower MICs than the wild-type for several antimicrobial agents such as penicillin G, methicillin, erythromycin and doxycycline. At ten days post infection the number of viable bacteria (disruption mutant) is markedly reduced compared to the wild-type. Belongs to the RelA/SpoT family.