R2B medium is used for the detection of heterotrophic bacteria in water, especially in treated potable water. This is a low-nutrient medium in which a combination of longer time and lower temperature of incubation promotes the growth of stressed and chlorine-treated bacteria. Enzymatic Digest of Casein and Animal Tissue provide nitrogenous sources for bacterial growth. Yeast Extract supplies B-complex vitamins and serves as growth enhancer. Dextrose is the fermentable carbohydrate. Soluble starch serves as neutralizer, while Sodium Pyruvate stimulates the growth of stressed bacteria. Dipotassium Phosphate and Magnesium Sulfate Heptahydrate act as pH buffers.