Culture media are nutrient-rich environments used in microbiology to grow and isolate various microorganisms. Different types exist, including supportive, enriched, selective, and differential media, each serving specific purposes based on the growth requirements of the microorganisms. Key historical figures like Louis Pasteur and Robert Koch contributed significantly to the development of culture media, utilizing various substances to enable microbial growth.

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