R2A agar (Reasoner's 2A agar) is a

culture medium A growth medium or culture medium is a solid, liquid, or semi-solid designed to support the growth of a population of microorganisms or cells via the process of cell proliferation or small plants like the moss ''Physcomitrella patens''. Different ...

developed to study

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

which normally inhabit

potable water Drinking water is water that is used in drink or food preparation; potable water is water that is safe to be used as drinking water. The amount of drinking water required to maintain good health varies, and depends on physical activity level, ag ...

. These bacteria tend to be slow-growing species and would quickly be suppressed by faster-growing species on a richer culture medium. Since its development in 1985, it has been found to allow the culturing of many other bacteria that will not readily grow on fuller, complex organic media.

Typical composition (% w/v)

Proteose A proteose is any of various water-soluble compounds that are produced during in-vitro or in-vivo hydrolytic breakdown of proteins a little before producing amino acids. It forms after breaking down of polypeptides by proteases such as gastric pep ...

peptone Peptides (, ) are short chains of amino acids linked by peptide bonds. Long chains of amino acids are called proteins. Chains of fewer than twenty amino acids are called oligopeptides, and include dipeptides, tripeptides, and tetrapeptides. A p ...

, 0.05% *

Casamino acids Casamino acids is a mixture of amino acids and some very small peptides obtained from acid hydrolysis of casein. It is typically used in microbial growth media. It has all the essential amino acids except tryptophan, which is destroyed by digestion ...

, 0.05% *

Yeast extract Yeast extracts consist of the cell contents of yeast without the cell walls; they are used as food additives or flavorings, or as nutrients for bacterial culture media. They are often used to create savory flavors and umami taste sensations, a ...

, 0.05% *

Dextrose Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, using ...

, 0.05% * Soluble starch, 0.05% * Dipotassium phosphate, 0.03% * Magnesium sulfate, 0.005% * Sodium pyruvate, 0.03% *

Agar Agar ( or ), or agar-agar, is a jelly-like substance consisting of polysaccharides obtained from the cell walls of some species of red algae, primarily from ogonori (''Gracilaria'') and "tengusa" (''Gelidiaceae''). As found in nature, agar is ...

, 1.5% Final pH 7 ± 0.2 @ 25 °C

References

{{Growth media Cell culture media