Often abbreviated to MRS, this type of bacterial growth medium

Growth medium

A growth medium or culture medium is a liquid or gel designed to support the growth of microorganisms or cells, or small plants like the moss Physcomitrella patens.There are different types of media for growing different types of cells....

 is so-named by its inventors: de Man, Rogosa and Sharpe. Developed in 1960, this medium was designed to favour the luxuriant growth of Lactobacilli for lab study. It contains sodium acetate

Sodium acetate

Sodium acetate, CH3COONa, also abbreviated NaOAc, also sodium ethanoate, is the sodium salt of acetic acid. This colourless salt has a wide range of uses.-Industrial:...

, which suppresses the growth of many competing bacteria (although some other Lactobacillales, like Leuconostoc

Leuconostoc

Leuconostoc is a genus of Gram-positive bacteria, placed within the family of Leuconostocaceae. They are generally ovoid cocci often forming chains. Leuconostoc spp. are intrinsically resistant to vancomycin and are catalase-negative . All species within this genus are heterofermentative and are...

and Pediococcus

Pediococcus

Pediococcus is a genus of Gram-positive lactic acid bacteria, placed within the family of Lactobacillaceae. They usually occur in pairs or tetrads, and divide along two planes of symmetry, as do the other lactic acid cocci genera Aerococcus and Tetragenococcus. They are purely homofermentative...

, may grow). This medium has a clear brown colour.

Typical composition

MRS agar typically contains(w/v

Percentage solution

"Percentage solution" is an ambiguous term which is used to describe a solution with the unit "%". It may refer to:* Mass fraction if mass/mass is meant...

):

• 1.0 % peptone
• 0.8 % meat extract
• 0.4 % yeast extract
  Yeast extract
  Yeast extract is the common name for various forms of processed yeast products made by extracting the cell contents ; they are used as food additives or flavourings, or as nutrients for bacterial culture media. They are often used to create savory flavors and umami taste sensations. Monosodium...
  
  
• 2.0 % glucose
  Glucose
  Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...
  
  
• 0.5 % sodium acetate
  Sodium acetate
  Sodium acetate, CH3COONa, also abbreviated NaOAc, also sodium ethanoate, is the sodium salt of acetic acid. This colourless salt has a wide range of uses.-Industrial:...
  
   trihydrate
• 0.1 % polysorbate 80
  Polysorbate 80
  Polysorbate 80 is a nonionic surfactant and emulsifier derived from polyethoxylated sorbitan and oleic acid, and is often used in foods. Polysorbate 80 is a viscous, water-soluble yellow liquid...
  
   (also known as Tween 80)
• 0.2 % dipotassium hydrogen phosphate
• 0.2 % triammonium citrate
• 0.02 % magnesium sulfate
  Magnesium sulfate
  Magnesium sulfate is a chemical compound containing magnesium, sulfur and oxygen, with the formula MgSO4. It is often encountered as the heptahydrate epsomite , commonly called Epsom salt, from the town of Epsom in Surrey, England, where the salt was distilled from the springs that arise where the...
  
   heptahydrate
• 0.005 % manganese sulfate tetrahydrate
• 1.0 % agar
  Agar
  Agar or agar-agar is a gelatinous substance derived from a polysaccharide that accumulates in the cell walls of agarophyte red algae. Throughout history into modern times, agar has been chiefly used as an ingredient in desserts throughout Asia and also as a solid substrate to contain culture medium...
  
  
• pH
  PH
  In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
  
   adjusted to 6.2 at 25°C

The yeast and meat extracts and peptone provide sources of carbon, nitrogen and vitamin

Vitamin

A vitamin is an organic compound required as a nutrient in tiny amounts by an organism. In other words, an organic chemical compound is called a vitamin when it cannot be synthesized in sufficient quantities by an organism, and must be obtained from the diet. Thus, the term is conditional both on...

s for general bacterial growth. The yeast extract also contains vitamins and amino acid

Amino acid

Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...

s specifically required by Lactobacilli. polysorbate 80

Polysorbate 80

Polysorbate 80 is a nonionic surfactant and emulsifier derived from polyethoxylated sorbitan and oleic acid, and is often used in foods. Polysorbate 80 is a viscous, water-soluble yellow liquid...

 is a surfactant which assists in nutrient uptake by Lactobacilli. Magnesium sulfate and manganese sulfate provide cations used in metabolism

Metabolism

Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...

.