CLASSIFICATIONS OF CULTURE MEDIA


A culture media is defined as solid or liquid preparation used to grow microorganisms.

CLASSIFICATIONS 

BASED ON CONSISTENCY

  • Liquid media
  • Semi-solid media
  • Solid media

Liquid media


Liquid media does not contain any solidifying agents. It is a good source of nutrients for the growth of nutrients of microorganisms.
Eg : Nutrient broth



Semi-Solid media

It remains in semi-solid state and prepared by adding small amount of Agar to the broth. It is used for the study of bacterial motility and cultivation of microorganisms.




Solid media

It is solid in consistency. It is also called agar medium. It is used for colony characterisation, colony identification and isolation of bacterial cells and demonstration of antibiotic sensitivity.



BASED ON COMPOSITION

  • Natural or Empirical media
  • Synthetic or chemically defined media
  • Complex media
  • Living media
  • Minimal media

Natural or Empirical media

Exact chemical composition of natural media is not known. These were widely used during the early stages of microbiology. The component of media include milk, vegetables, juices, blood, meat, etc. This type of medium is used on the basis of experience and observation and hence the name the name empirical medium.


Synthetic or chemically defined media

Synthetic media can be defined as an artificial media of known composition. The are prepared from media of known composition. They are prepared from pure chemical substances and are used for growth of majority of microorganisms.




 Complex media

Complex media contains undefined components like meat extract, yeast extract etc. It contains sources like enzymes, vitamins, Nitrogen and carbon.

Living media

These are group of living cells such as tissues, organs, etc used for growing some viruses and bacteria.

Minimal media
The media that lacks certain growth factors are termed as minimal media. It is used in genetic experiments.


BASED ON USES

  • Basal media
  • Enriched media
  • Enrichment media 
  • Selective media
  • Differential media/Indicator media
  • Transport media
  • Assay media
Basal media

  The common examples of simple or basal media are nutrient agar and nutrient broth. This media supports the growth of microorganisms that do not have special nutrient requirements.

Enriched media

It is used for cultivation of fastidious microorganisms (organisms with special nutrient requirements). Example for enriched media include blood agar, chocolate agar 




Enrichment media

It is a liquid media. It promotes the growth of a particular organism by providing it with nutrients. It contains certain inhibitory substance to prevent the growth of unwanted organisms. Example Selenite F broth
 


Selective media

It is used for growing selective organisms. It contains specified chemicals or dyes which prevents the growth of unwanted organisms while allows the growth of certain specific organisms.


 

Differential media/Indicator media

It contains dyes, chemicals or reagents which allows differentiation of organisms based on cultural characteristics. Example: Mac Conkey agar, Blood agar, Eosin methylene blue agar.

Transport media 

They are special medium formulated to preserve a specimen and to minimise bacterial overgrowth from the time of collection to the time if delivery at the laboratory to be processed in the sample, transport media may vary.
Examples: Stuart's media - Transport throat, vaginal, skin swabs that may contain gonococci

                  Cassy and Blair media - Transport media for transporting faecal sample that may contain Salmonella, Shigella, Vibrio, etc.

                   Venkataraman Ramakrishna [VR] media - For transporting Vibrio cholerae
                   

Assay media

For the assay of wide variety of antibiotics.

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