R-2A AGAR

R-2A Agar is a low-nutrient culture medium designed for the heterotrophic plate count of treated drinking water, where longer incubation is desired for the recovery of stressed and slow-growing microorganisms. It is the recommended standard method for heterotrophic bacterial enumeration by pour plate, spread plate and membrane filtration techniques.
In contrast to the nutrient-rich media, R-2A agar creates a lower nutrient environment that inhibits the outgrowth of fast-growing bacteria and allows for the growth of bacteria that are resistant to chlorine and stressed by the environment, such as those in treated water.
The medium contains casein acid hydrolysate, proteose peptone and yeast extract which provide the necessary nutrients, vitamins and trace elements for microbial growth. Dextrose is a fermentable carbohydrate Soluble starch is a recovery agent for injured microorganisms absorbing toxic metabolic by-products.
Sodium pyruvate also enhances the restoration of stressed cells and magnesium sulfate provides essential divalent cations. Dipotassium phosphate helps maintain the pH of the medium, while agar provides the solidifying matrix. The composition of R-2A Agar makes it ideal for accurate microbial count in analysis of treated drinking water.

A low-nutrient medium developed for heterotrophic plate counts of treated potable water, particularly for recovering stressed and chlorine-tolerant bacteria.