Background: ppGpp/DksA regulate genes both positively and negatively during stringency. Results: Positive control by ppGpp/DksA is linked to RNA polymerase-promoter saturation kinetics dependent on the promoter's discriminator. Conclusion: Promoters harboring discriminators that make them easily saturated with RNA polymerase are controlled positively by ppGpp/DksA. Significance: The discriminator is a cis-acting element dictating the response of the promoter to alterations in ppGpp/DksA and RNA polymerase availability.