Media helps to grow different microbes making it easier to study for research purpose.

1. TYPES OF culture MEDIA
SUBMITTED TO:- SUBMITTED BY:-
Dr. Suman Upadhyaya Anikesh Kr. Singh
M.Sc. FMT (1stSem)
DEM - BBAU

2. CULTURE MEDIUM
The food material on which microorganisms
are grown in the laboratory is known as
medium (pl. media) and the growth itself is
called a culture.

3. Types of culture media
Culture media can be classified on the basis of
following characterstics:
I. Consistency
II. Composition
III. Purpose

4. I. ON THE BASIS OF consistency
1. Solid medium
2. Semi-solid medium and
3. Liquid medium

5. 1. SOLID MEDIum
 'Agar' is most commonly used to prepare
solid medium.
Solid medium contains agar at a
concentration of 1.5-2.0%.
Agar is golden-yellow granular
powder obtained from seaweed.

6. CONT…
 It is basically a polysaccharide extract.
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.

7. Cont…
Solid medium has physical structure and allows
bacteria to grow in physically informative or
useful ways (e.g. as colonies or in streaks).
Advantages of 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.

8. 2. Semi-solid medium
They are prepared with agar at concentrations
of 0.5% or less.
They have soft custard like consistency.
They are useful in demonstrating bacterial
motility and separating motile from non-
motile strains.

10. 3. Liquid medium
They are sometimes referred as “ broth”.
These media contains specific amounts of
nutrients but don’t have any trace of gelling
agents such as gelatin or agar.
Broth medium serves various purposes such
as propagation of large number of organisms,
fermentation studies, and various other tests.
e.g. sugar fermentation tests.

11. Cont…
It is difficult to identify all type of
microorganisms in liquid medium.
Suitable for the isolation of bacteria from
blood culturing and water analysis.

12. II. ON THE BASIS OF COMPOSITION
1. Synthetic or chemically defined medium:-
 A chemically defined medium is one
prepared from purified ingredients and
whose exact composition is known.
 It provides trace elements and vitamins
required by the microbe and especially a
defined carbon and nitrogen source.

13. CONT…
Glucose or glycerol are often used as carbon
sources, and ammonium salts or nitrates as
inorganic nitrogen sources.
eg: peptone water –
1% peptone + 0.5% NaCl in water.

14. 2. Non synthetic or chemically undefined medium:-
 Non-synthetic medium contains at least one
component that is neither purified nor completely
characterized.
 Undefined medium has some complex ingredients,
such as yeast extract, which consists of a mixture of
many, many chemical species in unknown
proportions.
 For example- Nutrient broth, is derived from
cultures of yeasts

16. III. ON THE BASIS OF PURPOSE
1. General purpose media/ Basal Media.
2. Enriched medium.
3. Selective medium.
4. Differential/ indicator medium.
5. Transport media.
6. Anaerobic media.
7. Assay media.

17. 1. Basal media
Basal media are basically simple media that
supports most non-fastidious bacteria.
Peptone water, nutrient broth and nutrient
agar are considered as basal medium.
These media are generally used for the
primary isolation of microorganisms.

18. Nutrient Agar

19. 2. Enriched medium
Addition of extra nutrients in the form of
blood, serum, egg yolk etc, to basal medium
makes them enriched media.
Enriched media are used to grow nutritionally
exacting (fastidious) bacteria.

20. Cont…
Blood agar, chocolate agar, Loeffler’s serum
slope etc., are few of the enriched media.
Blood agar is prepared by adding 5-10% (by
volume) blood to a blood agar base.
Choclate agar is also known as heated blood
agar or lysed blood agar.

21. Blood Agar ChoclateAgar

22. 3. Selective medium
Selective and enrichment media are designed
to inhibit unwanted commensal or
contaminating bacteria and help to recover
pathogen from a mixture of bacteria.
While selective media are agar based,
enrichment media and are liquid in
consistency.

23. Cont…
Any agar media can be made selective by
addition of certain inhibitory agents that don’t
affect the pathogen of interest.
Various approaches to make a medium
selective include addition of antibiotics, dyes,
chemicals, alteration of pH or a combination
of these.

24. Cont…
 Examples of selective media include:
• Thayer Martin Agar used to recover N.gonorrhoeae.
• It usually contains the following combination of
antibiotics:
 Vancomycin: which is able to kill most Gram-positive
organisms.
 Colistin,: which is added to kill most Gram-negative
organisms except Neisseria.
 Nystatin,: which can kill most fungi.
 Trimethoprim: which inhibits Gram-negative
organisms.

25. Cont…
• Eosin methylene blue: selective for gram
negative bacteria
The dye methylene blue in the medium inhibit
the growth of gram positive bacteria

26. Cont…
• Lowenstein –Jenson medium is a
solid medium used for
Mycobacterium tuberculosis.
 It contain penicillin, nalidixic
acid and malachite green to
inhibit growth of gram positive
and gram negative bacteria, in
order to limit growth to
Mycobacteria species only.

27. Cont…
• Mannitol Salt Agar and Salt Milk Agar used to
recover S.aureus contains 10% NaCl.
• Selective media such as TCBS Agar used for
isolating V. cholerae from fecal specimens
have elevated pH (8.5-8.6), which inhibits
most other bacteria.

28. Cont…
• MacConkey’s Agar used
for Enterobacteriaceae members contains bile
salt that inhibits most gram positive bacteria.
• Wilson and Blair’s Agar for recovering S.
typhi is rendered selective by the addition of
dye brilliant green.

29. 4. Differential/ indicator medium
Certain media are designed in such a way that
different bacteria can be recognized on the basis
of their colony colour.
Various approaches include incorporation of
dyes, metabolic substrates etc, so that those
bacteria that utilize them appear as differently
coloured colonies.
Differential media allow the growth of more than
one microorganism of interest but with
morphologically distinguishable colonies.

30. Cont…
Examples of selective media include:
a) MacConkey medium: Distinguish between
lactose fermenters & non lactose fermenters.
• Lactose fermenters – Pink colonies
• Non lactose fermenters – colorless colonies

31. Cont…
b) Xylose Lysine Deoxycholate Agar(XLD): Used
for the recovery of Salmonella and Shigella
species.

32. Cont…
c) Cysteine Lactose Electrolyte Deficient
Agar(CLED): For cultivation of pathogen from
urine specimen, inhibit swarming of proteus sp.
CLED, serratia

33. 5. Transport media
Transport media is used for transporting the
samples.
Clinical specimens must be transported to the
laboratory immediately after collection to
prevent overgrowth of contaminating
organisms or commensals.
This can be achieved by using transport
media.

34. Cont…
Such media prevent drying (desiccation) of
specimen, maintain the pathogen to
commensal ratio and inhibit overgrowth of
unwanted bacteria.
Eg:
– Stuart’s medium
– Buffered glycerol saline

35. Cont…
Cary Blair transport medium and
VenkatramanRamakrishnan (VR) medium are
used to transport feces from suspected
cholera patients.
Sach’s buffered glycerol saline is used to
transport feces from patients suspected to be
suffering from bacillary dysentery.
Pike’s medium is used to transport
streptococci from throat specimens.

36. 6. Anaerobic media
These media are used to grow anaerobic
organisms.
Anaerobic bacteria need special media for
growth because they need low oxygen
content, reduced oxidation –reduction
potential and extra nutrients.
Media for anaerobes may have to be
supplemented with nutrients like hemin and
vitamin K.

37. Cont…
Such media may also have to be reduced by
physical or chemical means.
Addition of 1% glucose, 0.1% thioglycollate,
0.1% ascorbic acid, 0.05% cysteine or red hot
iron filings can reduce dissolve oxygen.
Before use the medium must be boiled in
water bath to expel any dissolved oxygen and
then sealed with sterile liquid paraffin.

38. Cont…
Example of anaerobic media are:
Robertson Cooked Meat (RCM) medium is
commonly used to grow Clostridium spps.
Thioglycollate broth contains sodium
thioglycollate, glucose, cystine, yeast extract and
casein hydrolysate.