Polyphosphate and associated enzymes as global regulators of stress response and virulence in Campylobacter jejuni

Figure 1 Model of poly P metabolism in Campylobacter jejuni. Phosphate esters are hydrolyzed to inorganic phosphate (Pi) by alkaline phosphatase (PhoAcj) in the periplasm. Phosphate uptake proteins and alkaline phosphatase are directly regulated by the PhosS/PhosR two-component system. Pi is transported across the inner membrane via the high affinity phosphate transport system PstSCAB. ATP generated from Pi is utilized for poly P synthesis by PPK1. PPK2 utilizes poly P to generate GTP, while PPX hydrolyzes poly P back to Pi. PPX also affects conversion of (p)ppGpp to ppGpp. SpoT is a bifunctional enzyme involved in both ppGpp synthesis as well as ppGpp hydrolysis. SpoT is also linked to poly P metabolism and a spoT mutant has reduced ability to accumulate poly P.