Type of Growth Medium

1. 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.

Physcomitrella patens plants growing axenically on agar plates (Petri dish, 9 cm diameter)

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

 

2. Minimal media

A defined medium that has just enough ingredients to support growth is called a "minimal medium". The number of ingredients that must be added to a minimal medium varies enormously depending on which microorganism is being grown. 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.

 

3. Selective media

Blood-free, charcoal-based selective medium agar (CSM) for isolation of Campylobacter

Blood agar plates are often used to diagnose infection. On the right is a positive Staphylococcus culture; on the left is a positive Streptococcus   culture.

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. Gancyclovir is an exception to the rule, as it is used to specifically kill cells that carry its respective marker, the Herpes simplex virus thymidine kinase.

Four types of agar plate demonstrating differential growth depending on bacterial metabolism

Examples of selective media include:

• Eosin methylene blue contains dyes that are toxic for Gram-positive bacteria. It is the selective and differential medium for coliforms.
• YM (yeast extract, malt extract agar) has a low pH, deterring bacterial growth.
• MacConkey agar is for Gram-negative bacteria.
• Hektoen enteric agar is selective for Gram-negative bacteria.
• HIS-selective medium is a type cell culture medium that lacks the amino acid histidine.
• Mannitol salt agar is selective for Gram-positive bacteria and differential for mannitol.
• Xylose lysine deoxycholate is selective for Gram-negative bacteria.
• Buffered charcoal yeast extract agar is selective for certain Gram-negative bacteria, especially Legionella pneumophila.
• Baird–Parker agar is for Gram-positive staphylococci.
• Sabouraud's agar is selective to certain fungi due to its low pH(5.6) and high glucose concentration(3-4%)
• DRBC (Dichloran Rose Bengal Chloramphenicol agar) is a selective medium for the enumeration of moulds and yeasts in foods. Dichloran and rose bengal restricts the growth of mould colonies thus preventing overgrowth of luxuriant species and assisting accurate counting of colonies.

 

4. Differential media

UTI Agar is a chromogenic medium for differentiation of main microorganisms that cause   urinary tract infections   (UTIs).

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, eosiny, 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:

• Blood agar (used in strep tests) contains bovine heart blood that becomes transparent in the presence of β-hemolytic organisms such as Streptococcus pyogenes and Staphylococcus aureus.
• Eosin methylene blue is differential for lactose fermentation.
• Granada medium is selective and differential for Streptococcus agalactiae (group B streptococcus) which grows as distinctive red colonies in this medium.
• MacConkey agar is differential for lactose fermentation.
• Mannitol salt agar is differential for mannitol fermentation.
• X-gal plates are differential for lac operon mutants.

5. 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:

• Thioglycolate broth is for strict anaerobes.
• Stuart transport medium is a non-nutrient soft agar gel containing a reducing agent to prevent oxidation, and charcoal to neutralize.
• Certain bacterial inhibitors are used for gonococci, and buffered glycerol saline for enteric bacilli.
• Venkataraman Ramakrishna (VR) medium is used for V. cholerae.

https://en.wikipedia.org/wiki/Growth_medium

배지의종류

 

Type of Growth Medium

 

PCR의 정의/작동원리/조건

 

Growth medium의 특징

 

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