1. CULTURE MEDIA

2. Microorganisms generally can use inorganic or organic N.
All micro-organisms require water, sources of energy, carbon, nitrogen, mineral element and vitamin plus oxygen in their growth medium.
1. Water
It is major component of all media. Following factors need to be considered about water for media preparation
Ø pH
Ø Dissolve salt
Ø Effluent contamination
2. Energy Sources
Energy for growth comes from either the oxidation of medium components or from light. The commonest sources of energy will be the carbon source such as carbohydrates, lipids and proteins.
3. Carbon sources
 Carbon requirement for the medium is normally provided by:
Ø Sucrose: Sugarcane, sugar beet molasses
Ø Glucose: Corn sugar, starch, cellulose
Ø Lactose: Milk whey
Ø Fats: Vegetable oil
Ø Starch: Maize grains, cereals, potatoes and cassava
4. Nitrogen Sources
 Microorganisms generally can use inorganic or organic N.
Ø Inorganic sources: ammonia, ammonium salts –
Ø Organic sources: amino acid, proteins and urea, Corn steep liquor, Yeast extract, Peptones, Soya bean meal.

3. Types of culture media
Based on their consistency
a) solid medium
b) liquid medium
Based on the constituents/ ingredients
a) simple medium
b) complex medium
c) synthetic or defined medium

4. Special media Enriched media Enrichment media Selective media
Indicator media
Differential media
Sugar media
Transport media

5. Solid media – contains 2% agar
Colony morphology, pigmentation, hemolysis can be appreciated.
Eg: LB agar, Nutrient agar, Blood agar
Liquid media – no agar.
For inoculum preparation, Blood culture, for the isolation of pathogens from a mixture.
Eg: Nutrient broth
Semi solid medium – 0.5% agar.
Eg: Motility medium

6. Simple media / basal media
Eg: NB, LB media
NB consists of peptone, meat extract, NaCl
NB + 2% agar = Nutrient agar
Complex media
Media other than basal media.
They have added ingredients.
Provide special nutrients.
Synthetic or defined media
Media prepared from pure chemical substances and its exact composition is known
Eg: peptone water – 1% peptone + 0.5% NaCl in water
Enriched media
Substances like blood, serum, egg are added to the basal medium.
Used to grow bacteria that are exacting in their nutritional needs.
Eg: Blood agar, Chocolate agar

7. Selective media LJ media
The inhibitory substance is added to a solid media.
Eg:
Mac Conkey’s medium for gram negative bacteria
Lowenstein Jensen medium – M. tuberculosis
Wilson and Blair medium – S. typhi
Potassium tellurite medium – Diphtheria bacilli
Mac Conkey’s medium
LJ media
Potassium Tellurite media

8. Differential media
A media which has substances incorporated in it enabling it to distinguish between bacteria.
Eg: Mac Conkey’s medium
Peptone
Lactose
Agar
Distinguish between lactose fermenters & non lactose fermenters.
Lactose fermenters – Pink colonies
Non lactose fermenters – colourless colonies

9. Media used for transporting the samples.
Transport media
Media used for transporting the samples.
Delicate organisms may not survive the time taken for transporting the specimen without a transport media.