culture media

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Culture Media

• Kashif haider
• BMLT 2nd sem

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Definition

• A growth media and culture media is a solid or
  liquid or semisolid designed to support the
  growth of microorganism or cell or small plant
  like the physcomitrella patens.

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Purpose /importance

• Bacteria have to be cultured in order to obtained
  antigens from developing serological assay for
  vaccines.
• Certain genetic studies and manipulation of the
  cell also need that bacteria be culture in vitro.

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History of culture media

• The original media used by Louis Pasteur were
  liquids such as urine or meat broths. liquid
  media have many disadvantages. Bacteria growing
  in them may not exhibit specific characteristics
  for their identification.
• Robert Koch realized the importance of
  solid media and used potato pieces to grow
  bacteria .it was on the suggestion of Fannie
  Eilshemius, wife of Walther Hesse(who was an
  assistant to Robert Koch)that agar was used to
  solidity culture media.
• Before the used agar, attempts were made use
  gelatin as solidifying agent . Gelatin had some
  inherent problem.
• It existed as liquid at normal incubating
  temperatures (35-37?)
• Digested by certain bacteria.

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Agar

• Agar is now universally used to prepare solid
  media. Agar is obtain from some type of seaweed.
  It also contain varying amounts of a protein like
  substance melt at 98? set at 42?

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Growth of bacteria

• During typical bacteria growth(growth cycle)
  bacteria cell divide by binary fission and their
  mass and number increase in an exponential
  manner. Bacteria growth in culture can be
  separated into at least four distinct phase.

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1. Lag phase

• This is period of intense physiological
  adjustment involving the induction of new enzymes
  and the synthesis and assembly of ribosome. In
  lad phase and during this phase occurs
• 1- increase in size of cells.
• 2- increase in metabolic rate.
• 3- adaptation to new environment and
  necessary enzymes.

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2-logarithmic(exponential) phase

• In logarithmic phase bacterial cell start
  dividing and their number increase by geometric
  progression with time.
• During this periods..
• 1- bacteria have high rate of metabolism
• 2- bacteria are more sensitive to
  antibiotics
• 3- rate of penetration of the medium it
  depend on the concentration of material in the
  media.

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Stationary phase

• In stationary phase after some time a stage comes
  when rate of multiplication and death becomes
  almost equal it may be due to
• 1- depletion of nutrient
• 2- accumulation of toxic product and
  sporulation may occur during this stage.

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Decline or death phase

• In decline (death) phase, during this phase
  population decreases due to death of cells the
  factors responsible are
• 1- nutritional exhaustion
• 2- toxic accumulation
• 3- autolysis enzymes

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Types of culture media base on
consistency Oxygen requirements ingredients
Solid media Aerobic media Simple media
Liquid media Anaerobic media Complex media
Semisolid media Synthetic media
Special media
Special media
Enriched media
Enrichment media
Selective media
Transport media
Sugar media
Indicator media
Differential media
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Solid Media

• Contains 2 agar
• Colony Morphology, Pigmentation, Hemolysis can be
  appreciated.
• E.g., Nutrient Agar, Blood Agar.
• Liquid Media
• No agar
• For Inoculum preparation, Blood Culture, For the
  Isolation of Pathogens from a mixture.
• E.g., Nutrient broth
• Semi Solid Medium
• 0.5 Agar
• E.g., SIM

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Simple media

• An example is nutrient broth. It consists of
  peptone, meat extract, sodium chloride and water.
  Nutrient agar made by adding 2 agar to nutrient
  broth is the simplest and most common media in
  routine diagnostics laboratories.

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Complex media

• These have added ingredients for special purpose
  or for bringing out certain characteristics or
  for providing special nutrients required for the
  growth of the bacterium under study.

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Synthetic or defined media

• These media are prepared from pure chemical
  substance and the exact composition of the media
  is fully documented. These are used for various
  special such as metabolic requirements.

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Enriched media

• In these media substance such as blood, serum or
  egg are added to a basal medium. They are used to
  grow bacteria which are more exacting in their
  nutritional needs.

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Enrichment media

• When a substance is added to a liquid medium
  which inhabit the growth of other bacteria and
  fever the growth of wanted bacteria it is known
  as enrichment media

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Selective media

• When a substance is added to a solid media which
  inhabit the growth of unwanted bacteria but
  permit the growth of wanted bacteria is called
  selective media

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Transport media

• Media used for transporting the samples.
• Delicate organism may not survive the time taken
  for transporting the specimen without a transport
  media.

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Sugar media

• It is used for the fermentation of the sugar like
  glucose, lactose, sucrose an mannitol, sugar
  media contain 1 sugar in peptone a small tubes.

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Indicator differential media

• When a substance is added into a medium which
  would produce a visible change in the particular
  organism it is called as well as differential
  media.