The Whatman™ ColiCheck with MUG Rapid Test Kit is used for the presumptive identification of coliforms and the determination of the presence of Escherichia coli in water samples by a presence/absence technique. The addition of MUG (4-methylumbelliferyl-b-D-glucuronide) which is a fluorogenic enzyme allows the media to selectively identify Escherichia coli. MUG is hydrolyzed by the Escherichia coli specific enzyme b-glucuronidase to release 4-methylumbelliferone which fluoresces under ultraviolet light (approx. 366 nm wavelength). Incubation at 30°C allows for the selective growth of Baker’s and Distiller’s yeast.