Nutritionally reduced medium. Incubation of water samples on R2A Agar often leads to higher colony numbers of micro organisms than found for rich media, particularly when incubation is performed at lower temperatures. The medium was originally developed by Reasoner and Geldreich to determine the total germ number in drinking water (Reasoner and Geldreich, 1985, Appl. Environ. Microbiol. 49:1). R2A-Agar, granulated acc. to Ph. Eur., granulated, for microbiology Nutritionally reduced medium. Incubation of water samples on R2A Agar often leads to higher colony numbers of micro organisms than found for rich media, particularly when incubation is performed at lower temperatures. Composition corresponds to Ph. Eur.