Urea Agar Base is used with added agar to detect urease activity by theEnterobacteriaceae. This lightly buffered medium contains Urea and Phenol Red as pH indicator. Urease activity alkalinizes the environment, thus producing a color shift from pale yellow to pink-red. Gelatin Peptone promotes rapid growth of enteric Gram-negative microorganisms, thus allowing for a reduction in the incubation time. In organisms that hydrolyze Urea slowly, Dextrose simulates urease activity. Agar is the gelifying agent.