This document discusses the classification and uses of culture media. Culture media contain nutrients that promote the growth of microorganisms. They can be classified based on consistency (solid, semisolid, liquid), nutritional components (simple, complex, synthetic), or application/chemical composition (basal, enriched, selective, indicator, transport, storage). Culture media are used to obtain pure cultures, grow and count microbial cells, and cultivate and select microorganisms. They allow for accurate microbiological testing and quality control.

1. KEERTHI VASAN R.
MICROBIOLOGY

2. • A mixture of substances that promotes and supports the growth and
differentiation of microorganisms.
• Culture media contain nutrients, energy sources, growth-promoting
factors, minerals, metals, buffer salts, and gelling agents.
• Some commonly used media components include peptone, agar, water,
casein hydrolysate, malt extract, meat extract, and yeast extract. In
addition, the pH of the medium should be set accordingly.

3. • A. Classification of culture media based on consistency.
• B. Classification based on the nutritional component.
• C. Classification of culture media based on application/chemical
composition.

4. A. Classification of culture media based on consistency.
1.Solid media:
In these media, the agar which is an unbranched long chain of
polysaccharides is added in the concentration of 1.5-2.0 %Most commonly,
1.3% agar is used to prepare solid media in labs. The agar-containing media
solidifies at 37 ºC.
Examples of solid media:
1.blood agar
2.Nutrient agar
3.McConkey agar

5. 2.Semisolid media.
• This media has 0.2-0.5% agar concentration, and due to the reduced agar
concentration, it appears as a soft, jelly-like substance.
• It’s mainly used to study the motility of microorganisms, distinguish
between motile and non-motile bacterial strains and cultivate
microaerophilic bacteria – bacteria on this media appear as a thick line.
• Examples of semi-solid media:
1.Stuart’s and Amies media
2.Mannitol motility media.

6. 3.Liquid media.
• These media do not contain any traces of solidifying agents, such as agar
or gelatin, and large growth of bacterial colonies can be observed in the
media.
• Liquid media are also called broths, they allow for uniform and turbid
growth of bacterial strains when incubated at 37ºC for 24hrs. The media
is used for the profuse growth of microorganisms and fermentation
studies.
• Examples:
Tryptic soy broth, phenol red carbohydrate broth, MR-VP broth,
and nutrient broth.

7. B. Classification based on the nutritional component.
1.Simple media:
• It’s a general-purpose media that supports the growth of non-fastidious
microbes, and it is primarily used for the isolation of microorganisms.
• Examples:
1.Nutrient broth.
2.Peptone water.
3.Nutrient agar.

8. 2.Complex media:
• These are media containing nutrients in unknown quantities that are
added to bring about a particular characteristic of a microbial strain.
Examples:
1.Tryptic soy broth.
2.Blood agar.
3.Nutrient broth.

9. 3.Synthetic media:
• Synthetic media is a type of chemically defined media and is produced
from pure chemical substances.
• A defined media refers to a medium having a known concentration of
ingredients, like sugar and nitrogen source (such as ammonium salt or
nitrate as inorganic nitrogen). It is generally used in scientific research,
Example:
Czapek Dox Medium.

10. C. Classification of culture media based on
application/chemical composition.
Types of Medium:
• (1) Basal media.
• (2) Enriched media.
• (3) Enrichment media
• (4) Selective .
• (5) Indicator media.
• (6) Transport media.
• (7) Storage media.
• (8) Anaerobic media.
• (9) Assay media.
• (10) Differential Media.

11. 1.BASAL MEDIA.
• Basal media are those that may be used for growth (culture) of bacteria
that do not need enrichment of the media.
• Examples:
1.Nutrient broth.
2.Nutrient agar.
Staphylococcus and Enterobacteriaceae grow in these media.

12. 2.ENRICHED MEDIA.
• The media are enriched usually by adding blood, serum or egg.
• Examples:
1.Enriched media are blood agar.
2.Lowenstein-Jensen media.
Streptococci grow in blood agar media.

13. 3. Enrichment media
• Enrichment media refers to the liquid media that inhibits the growth of
unwanted bacteria. Enriched media allow the growth of a wide variety of
microorganisms.
• Enrichment media allow the growth of a particular type of
microorganism in the medium.
• The enriched media facilitate the growth of fastidious microorganisms.
• Examples:
1.Blood agar
2.Chocolate agar
3.MacConkey agar and Lowenstein-Jensen media

14. 4.SELECTIVE MEDIA.
• These media favour the growth of a particular bacterium by inhibiting
the growth of undesired bacteria and allowing growth of desirable
bacteria.
• Examples:
1.MacConkey agar.
2.Lowenstein-Jensen media.
3.Tellurite media (Tellurite inhibits the growth of most of the throat
organisms except diphtheria bacilli). Antibiotic may be added.

15. 5.INDICATOR MEDIA.
• An indicator is included in the medium. A particular organism causes
change in the indicator, e.g. blood, neutral red, tellurite.
• Examples:
1.Blood agar.
2.MacConkey agar.
They are indicator media.

16. 6.TRANSPORT MEDIA.
• These media are used when specie-men cannot be cultured soon after
collection.
• Examples:
1.Cary-Blair medium.
2. Amies medium.
3.Stuart medium.

17. 7.STORAGE MEDIA.
• Media used for storing the bacteria for a long period of time.
• Examples:
1.Egg saline medium.
2.Chalk cooked meat broth.

18. 8.Anaerobic media.
• This media is for anaerobic bacteria which require low oxygen levels,
extra nutrients, and reduced oxidation-reduction potential.
• It is supplemented with hemin and vitamin K nutrients and oxygen is
removed by boiling it in a water bath and sealing it with paraffin film.
• Examples:
Thioglycollate broth and Robertson Cooked Meat (RCM) medium
which is commonly used to grow Clostridium spp

19. 9.Assay media.
• It’s used for amino acids, vitamins, and antibiotics assays.
• Example:
Antibiotic assay media is used to determine the antibiotic potency of
microorganisms.

20. 10.Differential Media:
• solation of bacteria is accomplished by growing (culturing) them on the
surface of solid nutrient media. Such a medium normally consists of a
mixture of protein digests and inorganic salts, hardened by the addition
of 1.5% agar.
• Differential media contain compounds that allow groups of
microorganisms to be visually distinguished by the appearance of the
colony or the surrounding media, usually on the basis of some
biochemical difference between the two groups.
• Examples:
MacConkey and EMB agars

21. USES OF CULTURE MEDIA
• To obtain pure cultures, to grow and count microbial cells, and to
cultivate and select microorganisms.
• Without high-quality media, the possibility of achieving accurate,
reproducible, and repeatable microbiological test results is reduced.
• Culture media are used for quality control tests of nonsterile raw
materials and finished products as well as for microbial contamination.