FIGURE 1.

(p)ppGpp modulates bacterial physiology at all growth stages. During adaptation (lag) and exponential (log) growth phases in the absence of stresses, basal levels of (p)ppGpp are important to maintain a balanced metabolism avoiding uncontrolled consumption of energy stores and toxic accumulation of metabolic byproducts. Entry into stationary growth phase or adverse condtions such as nutrient starvation, heat shock or selected antibiotic stresses triggers the accumulation of (p)ppGpp that rapidly reaches the threshold necessary to mount the SR responsible for remodeling cell physiology from a growth mode to a survival mode.