MRS Agar

De Man, Rogosa, and Sharpe created MRS Agar, a selective culture medium designed especially for the isolation and growth of lactic acid bacteria, especially lactobacilli. This media is commonly used in clinical microbiology, the dairy industry, and food microbiology. The lactobacilli’s growth is supported by the medium’s carefully adjusted composition, which simultaneously suppresses the growth of competing bacteria.
Meat extract and casein peptone are vital supplies of carbon and nitrogen, while glucose is the main carbohydrate used in energy metabolism. To provide B vitamins, which are essential for lactobacillus growth, yeast extract is added. Fatty acids become more soluble when tween 80 is added, which makes it easier for these bacteria to use them. Diammonium hydrogen citrate and sodium acetate are added to prevent the growth of unwanted microbes. For several enzymatic processes in lactobacilli, magnesium and manganese ions—provided by magnesium sulfate and manganese sulfate—are necessary cofactors. These acid-tolerant species depend on a steady pH, which is maintained by the phosphate buffer system.
Since lactobacilli are usually microaerophilic, lower oxygen tension is frequently necessary for their optimum growth. MRS agar is frequently used as a pour plate, with a second layer of sterile MRS agar placed on top of the solidified base layer following inoculation, to produce microaerophilic conditions.

Storage
Keep the container of dehydrated powder and prepared culture medium at 2 to 8 °C.