Culture medium contains nutrients to support microbial growth. The first media used meat extracts to culture pathogens. Media are classified by physical state as solid, semi-solid, or liquid, and by chemical composition as synthetic or undefined. Basal media support most bacteria while enriched media add blood or serum. Differential media identify microbial traits through indicators. Selective media allow specific microbes to grow by inhibiting others. Enrichment and transport media facilitate microbial isolation. Anaerobic media provide low oxygen conditions. Assay and storage media are used for enumeration, antibiotics testing, and long-term preservation, respectively.

1. CULTURE MEDIUM
PRESENTEDBY,
Jayapriya.R (BP211513)
I- MSc Applied Microbiology,
Sacreed Heart College,
Tirupattur.

2. CULTURE MEDIUM
 Culture Medium is an
 The culture media consist of chemicals (nutrients) which support the
growth of culture or microorganisms. Microbes can use the nutrients of
culture media as their food.
 The first medium prepared was . As most
pathogenic microbes require complex food similar in composition to the
fluids of the animal body, it was and his colleagues who
used meat infusion and meat extracts as basic ingredients in their culture
media for the isolation of pathogenic microbes.

3. The Culture Medium should contain
a) Carbon source (Carbohydrate sugars)
b) Various salts
c) Source of Amino acids and Nitrogen (Beef extract, Yeast extract,
Peptone, etc)
 Organisms that cannot grow in artificial culture medium are known as
(a parasitic organism that cannot complete its life cycle
without exploiting a suitable host).
 Example – Viruses, Mycobacterium leprae, Rickettsia sp., Chlamydia sp. and
Treponema pallidum.

4. CLASSIFICATION OF CULTURE MEDIUM
A) CLASSIFICATION OF CULTURE MEDIUM BASED ON
PHYSICAL STATE OR CONSISTENCY :
 Based on Physical state, the Culture medium was classified
into three types. They are
a)Solid medium
b)Semi – solid medium
c)Liquid medium or Broth

5. a) Solid Medium (Medium with Agar)
 Solid medium contains Agar at a concentration of 1.5 - 2.0%
or some other, mostly inert solidifying agent.
 Example – Nutrient Agar, MacConkey Agar, Sabouraud
Dextrose Agar, etc.
 Such media are used for making agar slants or slopes and
agar stab.

6. b) Semi - Solid Medium (Medium with minimum amount of agar)
 Semi – Solid Medium are prepared with agar at concentrations of 0.5% or less.
 Example – Sulfide Indole Motility Medium.
 They have soft custard like consistency and are useful for the cultivation of
Microaerophilic bacteria or for determination of bacterial motility.
c) Liquid Medium or Broth (Medium without Agar)
 The Culture medium without agar is called as Liquid medium or Broth.
 Example – Nutrient Broth, Sabouraud’s Dextrose Broth, etc.

7. B)CLASSIFICATION OF CULTURE MEDIUM BASED ON
CHEMICAL STATE
 Based on Chemical state, the Culture medium was classified into two
types. They are,
a) Synthetic or Chemically defined medium
 Synthetic or Chemically defined medium media are prepared by mixing
all the pure chemicals of known composition.
 Example – Nutrient Agar,MacConkey Agar,Sabouraud Dextrose
Agar,etc,.
b) Non – synthetic or Chemically undefined medium
 Non – synthetic or Chemically undefined medium media where exact
chemical composition is unknown.
 Example – Potato Dextrose Agar.

8. a)Basal Media:
 Basal media are basically simple media that contains basic nutrients and
supports most non-fastidious bacteria.
 Example
✓ Peptone water
✓ Nutrient broth
✓ Nutrient agar.
• Basal media are generally used for the primary isolation of
microorganisms.

9. b) Enriched Medium :
 The Basal medium enriched with Blood, Serum or Egg is called as
Enriched medium.
 Example
 Blood agar (Cooled Nutrient agar + 5 % Sheep Blood)
 Chocolate agar (Hot uncooled Nutrient agar + 5 % Sheep Blood)
 Lowenstein Jensen (LJ) Medium (Egg based medium for Mycobacterium
tuberculosis).

10. c) Differential or Indicator Medium :
 Differential medium is a medium which was used to differentiate the
characteristics of two microorganisms.
 An indicator (dye) is included in the medium. A particular organism
causes change in the colour of the indicator.
 Example
 MacConkey Agar (used to differentiate the Lactose fermenting and
Non – lactose fermenting bacteria).
 Blood Agar (used to differentiate the Hemolytic and Non – hemolytic
bacteria.

11. d) Selective Medium
 Selective medium is the medium that allows the growth of selective
microorganisms and inhibits the growth of other microorganisms.
 Example :
 Mannitol Salt Agar (MSA) - Staphylococcus aureus
 Thayer Martin Agar (TMA) – Neisseria gonorrhoeae
 Eosin Methylene Blue Agar (EMB) – Escherichia coli
 Salmonella – Shigella Agar (SSA) – Salmonella sp. and Shigella sp.

12. e) Enrichment Medium
 Enrichment medium is a medium which supports the growth of particular
organisms and do not supports the growth of other microorganisms.
 Example
 Selenite F broth
 Supports the growth of salmonella sp. and shigella sp. do not supports the
growth of E.coli

13. f) Transport Medium:
Transport medium is the medium which was used for the
transport of clinical samples.
Example
Cary Blair Transport Medium - Cholera
 Venkatraman Ramakrishnan (VR) Medium - Cholera

14. g) Anaerobic Medium :
 Anaerobic bacteria need special media for growth because they need low
oxygen content, reduced oxidation –reduction potential and extra nutrients.
 Anaerobic Medium is the medium used for the cultivation of Anaerobic
bacteria.
 Example
 Robertson Cooked Meat Medium (RCM) – Clostridium sp.

15. h) Assay Medium:
 Assay Medium is the medium used for the Enumeration of bacteria and
Assay of Antibiotics, Amino acids & Vitamins.
 Example :
 Mueller Hinton Agar (MHA) – Antibiotic assay.
 Standard Plate Count Agar (SPC) - Enumeration of bacteria.
i)Storage Medium :
 Media used for storing the bacteria for a long period of time.
 Example :
 Egg Saline Medium
 Chalk Cooked Meat Broth .