culture media, culturing, microbiological culture, types of culture medium, selective media, nutrient agar, enriched medium, beef broth

2. Dr. Qureshi Jalib (R.Ph)
Pharm-D, DHMS, B.ED

3. CULTURE MEDIA
Microbiological Culture
Method of cultivating microbial organisms by letting
them reproduce in predetermined culture media under
controlled laboratory conditions.

4. CULTURE MEDIA
Culture Medium
• A growth medium or culture medium is a solid, liquid
or semi-solid designed to support the growth of
microorganisms or cells, or small plants.
• Different types of media are used for growing
different types of cells.

5. CULTURE MEDIA
Purpose of Microbiological Culture
• Microbial cultures are used to determine the type of
organism, its abundance in the sample being tested, or
both.
• Bacteria have to be grown (cultured) for them to be
subsequent clinical diagnosis.
• Culturing bacteria is also the initial step in studying
its morphology and its identification.

6. CULTURE MEDIA
Purpose of Microbiological Culture
• By appropriate procedures they have to be grown
separately (isolated) on culture media and obtained as
pure for study.
• Culturing on solid media is another convenient way
of separating bacteria in mixture

7. CULTURE MEDIA
Importance of Microbiological Culture
• To obtain pure cultures,
• To grow and count microbial cells, and
• To cultivate and select microorganisms.
• Without high-quality media, the possibility of
achieving accurate, reproducible, and repeatable
microbiological test results is reduced

8. CULTURE MEDIA
Principle of Microbiological Culture
• In preparing a culture medium for any
microorganism, the primary goal is to provide a
balanced mixture of the required nutrients, at
concentrations that will permit good growth.
• No ingredient should be given in excess because
many nutrients become growth inhibitory or toxic as
the concentration is raised.

9. CULTURE MEDIA
Main Ingredients
• Nutrients: proteins/peptides/amino-acids.
• Energy: carbohydrates.
• Essential metals and minerals: calcium,
magnesium, iron, trace metals: phosphates, sulphates
etc.
• Buffering agents: phosphates, acetates etc.

10. CULTURE MEDIA
Main Ingredients
• Indicators for pH change: phenol red, bromo-cresol
purple etc.
• Selective agents: chemicals, antimicrobial agents.
• Gelling agent: usually agar.
• Growth Factors: to enhance growth. e.g. blood

11. CULTURE MEDIA
Types of Culture Media
 Natural Media
The media about which one cannot be certain of the exact
components or their quantity are called Natural Media for
Bacteria
 Synthetic media
Synthetic media are chemically defined. Here the nature and
amount of each component are known.

12. Natural media
Beef broth Nutrient agar Enriched media
Blood agar
Chocolate agar
Selective media
Mannitol Salt Agar
Eosin Methylene Blue Agar
Differential media

13. CULTURE MEDIA
Beef Broth
• Since the time of Pasteur and Koch, microbiologists have used
media such as beef broth for the laboratory cultivation of
bacteria.
– sugar
– non-iodized or sea salt
– beef broth
– Bring the volume up to 1 L with purified H2O

14. CULTURE MEDIA
Nutrient Agar
• The modern form of this liquid medium, called nutrient broth,
consists of:
– Water
– Beef extract
– Peptone
• Peptone is a protein supplement from plant or animal sources.
– Agar
• Agar is a polysaccharide derived from marine algae.
• It adds no nutrients to the medium but only serves to make it solid so that bacteria
can be cultivated on the surface.

15. CULTURE MEDIA

16. CULTURE MEDIA
Enriched medium
• Most common bacteria grow well in nutrient broth and nutrient
agar, but certain fastidious bacteria may require specially
enriched media.
– Blood Agar Media
– Chocolate Agar Media

17. CULTURE MEDIA
Blood Agar
Some the streptococci that cause strep throat and scarlet fever
grow well when whole blood is added to the nutrient medium.
In this instance, the medium is called blood agar.

18. CULTURE MEDIA
Chocolate Agar
To encourage the growth of Neisseria species, blood agar is
heated before solidification. Heating disrupts the red blood
cells and releases the hemoglobin. The medium is now termed
chocolate agar because of its charred brown appearance.

19. CULTURE MEDIA
Selective Media
Selective media contain ingredients to inhibit the
growth of certain bacteria in a mixture while
permitting the growth of others.
Mannitol Salt Agar
Eosin Methylene Blue Agar

20. CULTURE MEDIA
Mannitol Salt Agar
Staphylococci are cultivated-on mannitol salt agar.
This medium contains mannitol and a high salt
concentration that inhibits most other bacteria.
Mannitol is an alcoholic carbohydrate fermented by
staphylococci.

22. CULTURE MEDIA
Eosin Methylene Blue Agar
This selective medium has carbohydrates fermented
by E. coli and other Gram-negative bacteria. It also
contains eosin and methylene blue, two dyes that
inhibit Gram-positive bacteria.

23. Gram negative
bacteria/ Ecoli
Gram positive
bacteria

24. CULTURE MEDIA
Differential Media
Another type of medium is the differential medium.
This medium makes it easy to distinguish colonies of
one organism from colonies of other organisms on the
same plate.
Mac Conkey agar.

25. CULTURE MEDIA
MacConkey Agar
Mac Conkey agar is typical. It contains
The dyes neutral red and crystal violet
 Carbohydrate lactose
(Those bacteria that ferment the lactose take up the dyes and form red
colonies; other bacteria show up as colorless colonies)
MacConkey agar contains bile salts that inhibit the growth
of Gram-positive bacteria.
This medium is thus selective as well as differential.

27. CULTURE MEDIA
Synthetic Media
Synthetic media are chemically defined. Here the
nature and amount of each component are known.
Such a medium might contain
glucose,
ammonium phosphate,
potassium phosphate,
magnesium sulfate,
sodium chloride.

28. CULTURE MEDIA
Synthetic Media
• The glucose supplies energy to the cell;
• The ammonium ions are a source of nitrogen for amino acid
arid nucleic acid formation;
• Phosphate is used in DNA and RNA synthesis;
• Sulfur from magnesium sulfate is valuable for enzyme
formation;
• Sodium chloride maintains a stable internal environment in
the cytoplasm.

29. THANK
YOU!