What are Selective, Differential, Enriched, Nutrient and Minimal Media?

In microbiology, we use different type of media on routine basis. Different media have different properties and used for different type of microorganisms. Different types of media are mentioned below.

Selective Media:

Selective media are those media which are used to support growth of one group of microorganisms but inhibit the growth of other group of microorganisms. For example in case of Mannitol salt agar media. It contains very high amount of salt (7.5%) which inhibit the growth of gram negative bacteria and it is selective for gram positive bacteria like staphylococcus. MacConkey agar media is also selective for gram negative bacteria and other bacteria which found in the intestinal track. MacConkey agar contains bile salts and crystal violet which inhibit the growth of gram positive bacteria.

Differential Media:

Differential media are those media which are used to distinguish closely related microorganisms based on their morphology on different agar media. For example in case of Mannitol salt agar, it contains mannitol and phenol red as pH indicator which support the growth of mannitol fermenting staphylococcus. Acid produced due to mannitol fermentation is detected and due to presence of phenol red indicator dyestaphylococcus shows yellow coloured colonies on mannitol salt agar media. MacConkey agar is also differential media which contains lactose and it support the growth of lactose fermenting bacteria like E.coli.

MacConkey Agar Media                                                               Mannitol Salt Agar Media

So, media could be both selective as well as differential.

Nutrient media:

These media are also called general purpose media. These media are non selective and they contain general nutrients which required for the growth of wide range of microorganisms. Soyabean casein digest agar and Nutrient agar are the example of this type of media.

Enriched media:

These media support the growth of wide variety of microorganisms and doesn’t inhibit the growth of microorganisms. These media contains high amount of nutrients and mainly used to harvest the all types of microorganism which are present in the sample. For example Soyabean casein digest medium is used for enrichment of samples.

Minimal media:

Minimal media are those media which contains minimal nutrients for the growth of microorganisms. These media are mainly used for fastidious microorganisms. R2A media is an example of minimal media in which nutrients are present in very small amount.

List of media with Quantity, pH requirement and other Characteristics.