This ppt is on culture media used in microbiology study. Topics covered~ What is culture media?, Major contribution of scientist, Types of culture media~ physical nature, chemical composition, Basic requirements, Functional types, supportive media, media composition, enriched media, selective media, MacConkey agar composition, Differential media, selective & indicator media.

1. CULTURE
MEDIA

2. WHAT IS CULTURE MEDIA?
 A special medium containing all the required nutrients used to
grow different kinds of microorganisms in microbiology
laboratories.
 An important technique in microbiology and research to assist the
isolation, analysis and identification of microorganisms.
 Special media is used for different microorganisms as the growth
requirements are different.
 Testing antibiotic sensitivities, water & food analysis, industrial
microbiology, & other activities.

3. MAJOR CONTRIBUTION TO CULTURE MEDIA
 LOUIS PASTEUR (1822-95) – Used
simple broths made up of urine or
meat extracts.
 ROBERT KOCH (1843-1910) – Used
cooked potato pieces as solid
medium to grow bacteria.
-- used gelatine

4. TYPES OF CULTURE MEDIA
 Physical Nature
 Chemical Composition
 Functional type
➢PHYSICAL NATURE
• Broth that allows bacteria to
grow uniformly with turbidity.
• No agar
• For fermentation, blood
culture
• Ex: Nutrient broth
• Buth media has 0.5% agar
• Jelly consistency
• Ex: Mannitol motility
media.
• Contains 2% agar
• Isolation of bacteria as a pure
culture
• Allows growth of bacteria as
colonies.
• Ex. Nutrient agar, MacConkey
agar, Blood agar, Chocolate agar.

5. ➢ CHEMICAL COMPOSITION
 Also known as defined or synthetic medium
 Media prepared from pure chemical substance & its exact composition is known.
 Ex.; peptone water – 1% peptone + 0.5% NaCl in water

6. BASIC REQUIREMENTS OF CULTURE MEDIA
 Nutrients
- Energy source
- Carbon source
- Nitrogen source
 Mineral salts
– Sulphates, phosphates, chlorides
 Carbonates
– K, Mg & Ca.
 Suitable pH : 7.2 – 7.4
 Growth factors
• Amino acids - protein synthesis
• Purines & pyrimidines – nucleic acid synthesis
• Vitamins – functions as coenzymes

7. Functional types of
media

9. SUPPORTIVE MEDIA
 It contains nutrients that support and sustain growth of many microorganisms.
 These are general purpose , non-selective media provides nutrients to
variety of microorganisms.
 PH of supportive media 5.5-7.7
 Examples of supportive media : nutrient broth ,tryptic soy broth agar,
nutrient agar & nutrient broth.
 Tryptic soy agar is a solid media.
 Tryptic soy agar is growth media for bacteria.
 Aerobes and facultative anaerobes and some fungi grows.

10. MEDIA COMPOSITION

11. ENRICHED MEDIA
➢ Solid media
 When basal medium is added with some nutrients such as blood serum or egg it is called enriched media.
 Enriched with blood, serum , extra peptones ,egg & vitamins
 Used for cultivation of all fastidious micro-organisms, (Haemophiles influenza & streptococcus spp.)
 Examples : Blood agar media and chocolate agar media
➢ Blood agar
 Composition: sterile nutrient agar + 5-10% sheep blood
 Appearance : red color
 Most bacteria can grow on blood agar media
➢ Chocolate agar
 Chocolate agar → RBC breakdown → intracellular nutrients released
 Chocolate agar is different medium for gram positive cocci

12. SELECTIVE MEDIA
 They allow growth of one or more species.
 They also suppress the growth of other species, by one of the following.
1. Incorporating dyes
2. Antibiotics
3. Adjusting PH
4. Bile salts.
 EXAMPLE :
• MacConkey agar
• Salmonella – Shigella agar (S-S)
• Thayer martin medium
• Lowenstein Jensen medium
MacConkey Agar

13. MACCONKEY AGAR COMPOSITION

14. DIFFERENTIAL MEDIA
 When a medium contains substance which help to distinguish differing characteristics of bacteria is
called differential media.
 Lactose fermenters and non lactose fermenters
 Example : MacConkey agar
 It contains: peptone, agar, lactose, Neutral red (PH indicator), bile salts, Crystal violet.
 MacConkey agar is a differential media and selective media
 Gram negative enteric bacteria that grow on MacConkey agar are differentiated
by their ability to ferment lactose.
 If the lactose is fermented by the bacteria, the production of the acid drops the PH of the media.
 The drop in PH is indicated by the change of neutral red indicator to pink.
 If gram negative bacteria that grow on MacConkey agar but do not ferment lactose appear colorless on
the medium

15. SELECTIVE & INDICATOR/DIFFERENTIA MEDIA