page_title: Growth medium
section_title: Selective media
hierarchical_section_title: Growth medium / Types / Selective media
caption_attribution_description: English: Campylobacter jejuni colonies isolated on blood-free, charcoal based selective medium (CSM).
context_page_description: 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 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.
context_section_description: 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 (HSV TK).
  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.
caption: Blood-free, charcoal-based selective medium agar (CSM) for isolation of Campylobacter
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