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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''.〔Birgit Hadeler, Sirkka Scholz, Ralf Reski (1995) Gelrite and agar differently influence cytokinin-sensitivity of a moss. Journal of Plant Physiology 146, 369–371〕 There are different types of media for growing different types of cells. There are two major types of growth media: those used for cell culture, which use specific cell types derived from plants or animals, and microbiological culture, which are used for growing microorganisms, such as bacteria or yeast. The most common growth media for microorganisms are ''nutrient broths'' and agar plates; specialized media are sometimes required for microorganism and cell culture growth.〔 Some organisms, termed ''fastidious organisms'', require specialized environments due to complex nutritional requirements. Viruses, for example, are obligate intracellular parasites and require a growth medium containing living cells. == Types == The most common growth media for microorganisms are ''nutrient broths'' (liquid nutrient medium) or ''LB medium'' (''Lysogeny Broth''). Liquid media are often mixed with agar and poured via sterile media dispenser into Petri dishes to solidify. These agar plates provide a solid medium on which microbes may be cultured. They remain solid, as very few bacteria are able to decompose agar (the exception being some species in the following genera: ''Cytophaga'', ''Flavobacterium'', ''Bacillus'', ''Pseudomonas'', and ''Alcaligenes''). Bacteria grown in liquid cultures often form colloidal suspensions. The difference between growth media used for cell culture and those used for microbiological culture is that cells derived from whole organisms and grown in culture often cannot grow without the addition of, for instance, hormones or growth factors which usually occur ''in vivo''. In the case of animal cells, this difficulty is often addressed by the addition of blood serum or a synthetic serum replacement to the medium. In the case of microorganisms, there are no such limitations, as they are often unicellular organisms. One other major difference is that animal cells in culture are often grown on a flat surface to which they attach, and the medium is provided in a liquid form, which covers the cells. In contrast, bacteria such as ''Escherichia coli'' may be grown on solid media or in liquid media. An important distinction between growth media types is that of ''defined'' versus ''undefined'' media.〔 A defined medium will have known quantities of all ingredients. For microorganisms, they consist of providing trace elements and vitamins required by the microbe and especially a defined carbon source and nitrogen source. Glucose or glycerol are often used as carbon sources, and ammonium salts or nitrates as inorganic nitrogen sources. An undefined medium has some complex ingredients, such as yeast extract or casein hydrolysate, which consist of a mixture of many, many chemical species in unknown proportions. Undefined media are sometimes chosen based on price and sometimes by necessity – some microorganisms have never been cultured on defined media. A good example of a growth medium is the wort used to make beer. The wort contains all the nutrients required for yeast growth, and under anaerobic conditions, alcohol is produced. When the fermentation process is complete, the combination of medium and dormant microbes, now beer, is ready for consumption. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Growth medium」の詳細全文を読む スポンサード リンク
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