MRS agar

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Selective culture medium for Lactobacilli

title: "MRS agar" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["microbiological-media"] description: "Selective culture medium for Lactobacilli" topic_path: "philosophy" source: "https://en.wikipedia.org/wiki/MRS_agar" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Selective culture medium for Lactobacilli ::

::figure[src="https://upload.wikimedia.org/wikipedia/commons/a/a9/Pediococcus_acidilactici_on_TSA.jpg" caption="''Pediococcus acidilactici'' colonies on an '''MRS agar''' plate"] ::

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, , , and . 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.

Typical composition

MRS agar typically contains (w/v):

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.

References

EMD Chemicals, [http://www.emdchemicals.com/analytics/Micro_Manual/TEDISdata/prods/1_10660_0500.html MRS Agar] {{webarchive. link. (2009-04-30 , 2002.)
(1960). "A Medium for the Cultivation of ''Lactobacilli''". Journal of Applied Bacteriology.

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