A growth medium or culture medium is a solid, liquid or semi-solid designed to support the growth of microorganisms or cells, or small plants like the moss Physcomitrella patens. Different types of media are used for growing different types of cells. The two major types of growth media are 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 fungi. 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.
1.1 Culture media 1.2 Minimal media 1.3 Selective media 1.4 Differential media 1.5 Transport media
2 Enriched media 3 See also 4 References 5 External links
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 a 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 genera: Cytophaga, Flavobacterium, Bacillus,
Pseudomonas, and Alcaligenes).
Cultural media Minimal media Selective media Differential media Transport media Indicator media
Culture media Culture media contain all the elements that most bacteria need for growth and are not selective, so they are used for the general cultivation and maintenance of bacteria kept in laboratory culture collections.
An undefined medium (also known as a basal or complex medium) contains:
a carbon source such as glucose water various salts a source of amino acids and nitrogen (e.g., beef, yeast extract)
This is an undefined medium because the amino-acid source contains a variety of compounds with the exact composition being unknown.
A defined medium (also known as chemically defined medium or synthetic medium) is a medium in which
all the chemicals used are known no yeast, animal, or plant tissue is present
Some examples of nutrient media include:
Plate count agar Nutrient agar Trypticase soy agar
Minimal media Minimal media are those that contain the minimum nutrients possible for colony growth, generally without the presence of amino acids, and are often used by microbiologists and geneticists to grow "wild-type" microorganisms. Minimal media can also be used to select for or against recombinants or exconjugants. Minimal medium typically contains:
a carbon source, which may be a sugar such as glucose, or a less energy-rich source such as succinate various salts, which may vary among bacteria species and growing conditions; these generally provide essential elements such as magnesium, nitrogen, phosphorus, and sulfur to allow the bacteria to synthesize protein and nucleic acids water
Supplementary minimal media are minimal media that also contains a single selected agent, usually an amino acid or a sugar. This supplementation allows for the culturing of specific lines of auxotrophic recombinants. Selective media
Blood-free, charcoal-based selective medium agar (CSM) for isolation of Campylobacter
Selective media are used for the growth of only selected
microorganisms. For example, if a microorganism is resistant to a
certain antibiotic, such as ampicillin or tetracycline, then that
antibiotic can be added to the medium to prevent other cells, which do
not possess the resistance, from growing. Media lacking an amino acid
such as proline in conjunction with E. coli unable to synthesize it
were commonly used by geneticists before the emergence of genomics to
map bacterial chromosomes.
Selective growth media are also used in cell culture to ensure the
survival or proliferation of cells with certain properties, such as
antibiotic resistance or the ability to synthesize a certain
metabolite. Normally, the presence of a specific gene or an allele of
a gene confers upon the cell the ability to grow in the selective
medium. In such cases, the gene is termed a marker.
Selective growth media for eukaryotic cells commonly contain neomycin
to select cells that have been successfully transfected with a plasmid
carrying the neomycin resistance gene as a marker.
Four types of agar plate demonstrating differential growth depending on bacterial metabolism
Examples of selective media include:
Eosin methylene blue
Differential media Differential or indicator media distinguish one microorganism type from another growing on the same medium. This type of media uses the biochemical characteristics of a microorganism growing in the presence of specific nutrients or indicators (such as neutral red, phenol red, eosin y, or methylene blue) added to the medium to visibly indicate the defining characteristics of a microorganism. These media are used for the detection of microorganisms and by molecular biologists to detect recombinant strains of bacteria. Examples of differential media include:
Transport media Transport media should fulfill these criteria:
Temporary storage of specimens being transported to the laboratory for cultivation Maintain the viability of all organisms in the specimen without altering their concentration Contain only buffers and salt Lack of carbon, nitrogen, and organic growth factors so as to prevent microbial multiplication Transport media used in the isolation of anaerobes must be free of molecular oxygen
Examples of transport media include:
Enriched media contain the nutrients required to support the growth of
a wide variety of organisms, including some of the more fastidious
ones. They are commonly used to harvest as many different types of
microbes as are present in the specimen.
Cell culture Impedance microbiology Modified Chee's medium
^ a b c Madigan M, Martinko J, eds. (2005). Brock Biology of
Microorganisms (11th ed.). Prentice Hall.
^ Birgit Hadeler, Sirkka Scholz,
The Nutrient Requirements of Cells
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Growth media / agar plates
Löwenstein–Jensen medium Middlebrook 7H9 Broth Middlebrook 7H10 Agar Middlebrook 7H11 Agar
Bile esculin agar
Mannitol salt agar
Haemophilus influenzae/Legionella pneumophila
Buffered charcoal yeast extract agar
DCA agar Salmonella/Shigella
MacConkey agar/Sorbitol-MacConkey agar
Hektoen enteric agar sulfur
Bismuth sulfite agar
Czapek medium Dermatophyte test medium Potato dextrose agar Sabouraud agar
Chocolate agar Nutrient agar Plate count agar
Cystine lactose electrolyte deficient agar Cystine tryptic agar Endo agar Lysine iron agar slant Müller-Hinton agar/PNP agar R2a agar Simmons' citrate agar Trypticase soy agar Tryptic soy broth TSI slant