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1. MEDIA PREPARATION

2.  Microbes require to grow
1) Nutrients
2) An energy source
3) Environmental conditions
 These are supplied by culture media
Solid Media
 Bacteria may be identified by studying the colony character
 Mixed bacteria can be separated
 Solid media is used for the isolation of bacteria as pure culture.

3.  Agar is polysaccharide extract obtained from seaweed.
 Agar is an ideal solidifying agent as it is :
 Bacteriologically inert, i.e. no influence on bacterial growth
 It remains solid at 37°C
 It is transparent
Liquid Media
It is used for growth of bacteria
Mixed organisms cannot be separated

4. COMPLEX MEDIA
Rich in nutrients, contain water soluble extracts of plant or animal
tissues Usually a sugar, often glucose is added to serve as the main
carbon and energy source. The combination of extracts and sugar
creates a medium which is rich in minerals and organic nutrients,
but since the exact composition is unknown, the medium is called
complex.
DEFINED MEDIA
are media composed of pure ingredients in carefully measured
concentrations dissolved in double distilled water i.e., the exact
chemical composition of an inorganic nitrogen source, various
mineral salts and if necessary growth factors
Categories:

5. SELECTIVE MEDIA
These media favour the growth of a particular bacterium by inhibiting the
growth of undesired bacteria and allowing growth of desirable bacteria.
Example MacConkey agar.
DIFFERENTIAL MEDIA
An indicator is included in the medium. A particular organism causes
change in the indicator. Examples: Blood agar and MacConkey agar.
EMB (Eosin methylene blue agar)
E. coli (green color) Salmonella (colourless)

6. ENRICHED MEDIA
The media are enriched usually by adding blood or serum. Examples:
Enriched media are blood agar
Streptococci grow in blood agar media

7.  Weighing of solid media and water
 Mixing on magnetic stirrer
 pH adjustment accordingly
 Pouring in case of liquid media
 Autoclaving
 Pouring of solid media in sterilized petri plates