MICROBIAL CULTURING AND MEDIA TYPES

1. MICRO-
ORGANISM
METHODS OF CULTURING
MEDIA FOR MICROBIAL GROWTH

2. Culture Methods
 A microbiological culture, or microbial
culture
 Microbial cultures are used to determine the
type of organism
 It is often essential to isolate a pure culture
of microorganisms.
 A pure culture may originate from a single
cell or single organism
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3. Bacterial culture
 Grow in
 Agar-based growth medium
 Liquid culture
 In which the desired bacteria are suspended in liquid
broth, a nutrient medium.
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4. Once the growth medium in the petri dish is inoculated with the
desired bacteria, the plates are incubated at the best temperature for
the growing of the selected bacteria (for example, usually at 37 degrees
Celsius for cultures from humans or animals, or lower for
environmental cultures).
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5. Colony– Macroscopically visible collection of millions of bacteria
originating from a single bacterial cell.
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6. Culture
Mixed culture
 Holds two or more
identified species
Contaminated
culture
 Includes unwanted
microorganisms, or
contaminants.
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7. Types of culture methods
1. Streak culture or surface plating
2. Lawn or carpet culture
3. Stroke culture
4. Stab culture
5. Pour plate method
6. Broth Culture
7. Anaerobic methods of culturing bacteria
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8. 1. Streak
Culture
 Routinely
employed for
isolation
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10. 2. Lawn or Carpet Culture
 Uniform surface growth
 Antibiotic sensitivity testing
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11. 3.Stroke Culture
 Tubes containing agar slopes
 For stock culture
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13. 5. Pour Plate Method
 Colonies appear through out the
depth of medium.
 Used to estimate viable count,
recommended method for
quantitative cultures.
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14. 6. Broth Culture
 Growing micro organism that is
found in a liquid nutrition
medium
 Inoculated by a charged loop,
pipette or syringes.
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15. 7. Anaerobic Culture
Methods
 Anaerobic condition can be achieved by
1. Displacement of O2 with other gases.
2. Absorption of O2 by chemical or biological means
3. Reduction of O2
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16. 1. Displacement Method
 Displacement of O2 with
gases like H2 , N2 , He or
CO2 .
 Rarely produces
complete anaerobiosis.
e.g. Candle jar
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17. 2. Absorption of O2 by chemical or biological
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18. Agar
 A gelatinous substance obtained from certain
red seaweeds and used in biological culture
media.
 Frau Hesse initial suggestion of using agar as an
alternative to gelatin, they were instrumental in
pioneering agar's usage as a common gelling agent for
producing media capable of culturing microorganisms
at high temperatures
 Solid at room temp(at 42oC)
 Melts at boiling (100oC)
 Will re-solidify when cooled
 Complex polysaccharide
 Used for preparing solid medium
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19. Types of culture media
I. Based on their consistency
a) solid medium
b) liquid medium
c) semi solid medium
II. Based on the constituents/ ingredients
a) simple medium
b) complex medium
c) synthetic or defined medium
d) Special media
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20. Special media
 Enrichment media
 Selective media
 Indicator media
 Differential media
 Sugar media
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21. BREAK
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22. Classification of media
By Physical State :
•Liquid Media
•Semisolid Media
•Solid Media that are
liquifiable
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24. Media by Physical State
(LIQUID)
 Water-based solutions, do not solidify at
temperatures above freezing
•broths, milks, or infusions
•growth seen as cloudiness or particulates
 No agar.
 Eg: nutrient broth
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25. Media by Physical State
(SEMISOLID)
 Clot-like consistency at room temperature
used to determine motility and to localize reactions at
a specific site
 0.5% agar.
 Eg: motility medium
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26. Media by Physical State (SOLID)
 A firm surface on which cells can form discrete colonies
•useful for isolating and culturing bacteria and fungi
 Contains 2% agar
 Colony morphology, pigmentation, hemolysis can be
appreciated.
 Eg: nutrient agar, blood agar
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27. Classification of media
 By Chemical composition :
 Simple medium
 Defined or Synthetic media-
 Complex or Non-synthetic media-
 Special media
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28. Simple media / basal media
 Supports most non-fastidious bacteria.
- Eg: NB, NA
- NB consists of peptone, meat extract, NaCl,
- NB + 2% agar = Nutrient agar
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29. Defined or Synthetic media-
 Compositions are precisely chemically defined
 Media prepared from pure chemical substances and its
exact composition is known
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30. Complex or Non-synthetic
media-
 Whose exact concentration of ingredients is not
known
 They have added ingredients.
 Provide special nutrients
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31. Special media
 Enrichment media
 Selective media
 Differential media
 Indicator media
 Sugar media
 Assay media
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32. Enrichment media
 Liquid media used to isolate pathogens from a mixed culture.
 Media is incorporated with inhibitory substances to suppress the
unwanted organism.
 Eg:
 Selenite F Broth – for the isolation of Salmonella, Shigella
 Alkaline Peptone Water – for Vibrio cholerae
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33. Selective media-
 Contains one or more agents that inhibit the growth of
certain microbes but not others.
 The inhibitory substance is added to a solid media.
Eg:
 Mac Conkey’s medium for gram negative bacteria
 TCBS – for V.cholerae
 LJ medium – M.tuberculosis
 Wilson and Blair medium – S.typhi
 Potassium tellurite medium – Diphtheria bacilli
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34. TCBS
Vibreo Cholera
Mac Conkey’s medium
Gram negative
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35. Potassium Tellurite media
Diphtheria bacilli
LJ media
M.Tuberculosis
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36. Differential media-
 A media which has substances incorporated in it
enabling it to distinguish between bacteria.
 Macconkey agar can be used as a differential medium
as well.
 Distinguish between lactose fermenters & non lactose
fermenters.
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37.  Lactose fermenters – Pink colonies
 Non lactose fermenters – colourless colonies
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38. Indicator media
 These media contain an indicator which changes its colour when a
bacterium grows in them.
 Eg:
 Blood agar
 Mac Conkey’s medium
 Christensen’s urease medium
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39. Urease medium
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40. Carbohydrate fermentation
media
(Sugar media)
 Contain sugars & a pH indicator
 Contain a small tube (Durham’s tube) for the detection
of gas by the bacteria.
 A fermentation medium consists of a basal medium
containing a single carbohydrate (glucose, lactose,
sucrose, mannitol etc.)
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42. THANK YOU!
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