MRS agar

Often abbreviated to MRS, this type of bacterial growth medium is so-mamed by its inventors: de Man, Rogosa and Sharp. Developed in 1960, this medium was designed to favour the luxuriant growth of lactobacilli for lab study. It contains sodium acetate, which suppresses the growth of many competing bacteria.

Typical Composition (g/l)
Peptone, 10

Meat extract, 8

Yeast extract, 4

Glucose, 20

Sodium acetate 3H2O, 5

Tween 80, 1

Dipotassium hydrogen phosphate, 2

Triammonium citrate, 2

Magnesium sulfate 7H2O, 0.2

Manganese sulfate 4H2O, 0.05

Agar, 10

Final pH 6.2 @ 25°C

The yeast and meat extracts and peptone provide sources of carbon, nitrogen and vitamins for general bacterial growth. The yeast extract also contains vitamins and amino acids specifically required by lactobacilli. Tween 80 is a surfactant which assists in nutrient uptake by lactobacilli. Magnesium sulfate and manganese sulfate provide cations used in metabolism.