2. Culture: Is the term given to microorganisms that are
Cultivated in the lab for the purpose of identifying and
studying them.
Medium: is the term given to the combination of ingredients that
will support the growth and cultivation of microorganisms by
providing all the essential nutrients required for the growth (i.e.
multiplication) in order to cultivate these.
Introduction
3. Culture Media: Also Known as Growth Media, are
Specific Mixtures of Nutrients and Other Substances that
Support the Growth of Microorganisms Such as Bacteria
and Fungi (Yeasts And Molds).
Microbial culture media should provide optimal growth
conditions for all or specific types of microorganisms.
The precise (exact) composition of a medium depends on
the species being cultivated and the application goal. The
medium pH needs to be adjusted depending on the
microorganisms.
4.
5. Agar
• Frau Hesse
• Used for preparing solid medium
• Obtained from seaweeds.
• No nutritive value
• Not affected by the growth of the bacteria.
• Melts at 98oC & sets at 42oC
• 2% agar is employed in solid medium
6. Microbial Culture Media Preparation
• Media is measure - a specific quantity of dry powdered
nutrient media, add water and check the pH(7).
•Dispense the media into bottles (flask, tube), cap it and
autoclave. The autoclave exposes the media to high
temperature (121°C) and pressure (15 psi) for 20 minutes.
•Once the media is autoclaved it is sterile
• (all micro-organism forms killed)
13. Normal Flora Samples
• Important to remember that microbes are (everywhere)!
• We are inhabited (covered) by many different bacteria. .
• Most of the symbiotic relationships that we have with microbes
are beneficial to both the microbe and us!
• In today's lab we will examine normal flora (hand. hair. skin)
15. • Place all inoculated material in incubator Culture tubes
should be stored upright in plastic beakers, while Petri
plates should be incubated upside-down (lid on the bottom )
19. Types of Culture Media
Microbial culture media is classified based on several
parameters, like chemical constituents, physical nature, and
function.
Types of media defined by these parameters are described
below.
20. 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
21. Special Media
• Enriched media
• Enrichment media
• Selective media
• Indicator media
• Differential media
• Sugar media
• Transport media
• Media for biochemical reactions
III. Based on Oxygen requirement
- Aerobic media
- Anaerobic media
22. Solid media – contains 2% agar
Colony morphology, pigmentation, hemolysis can be appreciated.
• Eg: Nutrient agar, Blood agar
Liquid media ( Broth)– no agar.
• For inoculum preparation, Blood culture, for the isolation of
pathogens from a mixture.
• Eg: Nutrient broth
Semi solid medium – 0.5% agar.
• Eg: Motility medium
24. Simple media / basal media
- Eg: Nutrient Broth, Nutrient Agar
- Nutrient Broth consists of peptone, meat extract, NaCl,
- NB + 2% agar = Nutrient agar
25. Complex media
• Media other than basal media.
• They have added ingredients.
• Provide special nutrients
Synthetic or defined media
• Media prepared from pure chemical substances and its exact
composition is known
• Eg: peptone water – 1% peptone + 0.5% NaCl in water
26. Enriched media
• Substances like blood, serum, egg are added to the basal medium.
• Used to grow bacteria that are exacting in their nutritional needs.
• Eg: Blood agar, Chocolate agar
28. • This media is differential because:
• Certain bacteria produce enzymes (hemolysins…) that act on the
red cells to produce either:
• Beta hemolysis: Enzymes lyse the blood cells completely,
producing a clear area around the colony.
• Alpha hemolysis: Incomplete hemolysis produces a
greenish discoloration around the colony
• Gamma hemolysis: No effect on the red cells.
29. 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
30. Selective media
• culture medium that allows the growth of one type of organisms,
while inhibiting the growth of other organisms
•The inhibitory substance is added to a solid media. Eg: Mac
Conkey’s medium for gram negative bacteria
• Thiosulphate Citrate Bile Salt Sucrose Agar – for V. cholerae
• Lowenstein Jensen medium – M. tuberculosis
• Wilson and Blair medium – S. typhi
• Potassium tellurite medium – Diphtheria bacilli
• EMB (Eosin Methylene Blue)
• dyes inhibit Gram (+) bacteria. Selects for Gram (-) bacteria
33. 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
36. Differential media
• A media which has substances incorporated in it enabling it to
distinguish between bacteria.
• Eg: Mac Conkey’s medium
• Peptone
• Lactose
• Agar
• Neutral red
• Taurocholate
• Distinguish between lactose fermenters & non lactose fermenters.
38. MacConkey's
• MacConkey’s is both a selective & differential media.
• MacConkey’s is selective media because it inhibits the growth of
some organisms [Gram positive bacteria].
2. MacConkey’s is differential media
• - “lactose fermenters” bacteria will grow in red colonies while” non-
lactose fermenters” will be colorless and clear.
39.
40. left: no lactose fermentation right:
lactose fermentation
So if there are colonies of bacteria growing on MacConkey’s, it’s understood that
they are Gram-
If those colonies are colorless, they are not lactose fermenters. If the colonies have a
pinkish appearance, they are lactose fermenters
MacConkey Agar
41. Sugar media
• Media containing any fermentable substance.
• Eg: glucose, arabinose, lactose, starch etc.
• Media consists of 1% of the sugar in peptone water.
• Contain a small tube (Durham’s tube) for the detection of gas by the
bacteria.
42.
43. Transport media
• Media used for transporting the samples.
• Delicate organisms may not survive the time taken for
transporting the specimen without a transport media.
• Eg:
• Stuart’s medium – non nutrient soft agar gel containing a
reducing agent
• Buffered glycerol saline – enteric bacilli
44. Anaerobic media
• These media are used to grow anaerobic organisms.
• Eg: Robertson’s cooked meat medium,
Thioglycolate medium.
