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MRS agar
Selective culture medium for Lactobacilli From Wikipedia, the free encyclopedia
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De Man–Rogosa–Sharpe agar, often abbreviated to MRS, is a selective culture medium designed to favour the luxuriant growth of Lactobacilli for lab study. Developed in 1960, this medium was named for its inventors, Johannes Cornelis de Man , Morrison Rogosa , and Margaret Elisabeth Sharpe . It contains sodium acetate, which suppresses the growth of many competing bacteria (although some other Lactobacillales, like Leuconostoc and Pediococcus, may grow). This medium has a clear brown colour.[1]

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Typical composition
MRS agar typically contains (w/v):[2]
- 1.0% peptone
- 1.0% beef extract
- 0.4% yeast extract
- 2.0% glucose
- 0.5% sodium acetate trihydrate
- 0.1% polysorbate 80 (also known as Tween 80)
- 0.2% dipotassium hydrogen phosphate
- 0.2% triammonium citrate
- 0.02% magnesium sulfate heptahydrate
- 0.005% manganese sulfate tetrahydrate
- 1.0% agar
- pH adjusted to 6.2 at 25 °C
The yeast/meat extracts and peptone provide sources of carbon, nitrogen, and vitamins for general bacterial growth. The yeast extract also contains vitamins and amino acids required by Lactobacilli. Polysorbate 80 is a surfactant which assists in nutrient uptake by Lactobacilli. Magnesium sulfate and manganese sulfate provide cations used in metabolism.
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See also
- MacConkey agar (culture medium designed to grow Gram-negative bacteria and differentiate them for lactose fermentation).
References
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