Galope, Sharcele Rovi S.
BMLS 3C
PRELIMS #5
CULTURE MEDIA
Culture medium – nutrients for microbial
growth
Inoculum – microbes introduced into the
medium
Culture –microbes growing in/on culture
medium
Pure culture – contains only one species or
strain
Colony – A population of cells arising from a
single cell or spore
Agar – solidifying agent for culture media
(liquefies at 100 degrees Celsius, solidifies at 40
degrees Celsius
Selective Media
o Suppresses unwanted microbes
o Encourage desired microbes
Differential Media
o Make it easy to distinguish colonies of
different microbes
Enrichment Media
o Encourages growth of desired microbes
Streak Plate
o Preserving Bacterial Cultures
 Deep – freezing: -50°C to -95°C
 Lyophilization – Frozen (-54°C to
-72°C) and dehydrated in a
vacuum
Culture medium
- The biochemical (nutritional)
environment is made available
- Employed in the isolation and
maintenance of pure cultures of
bacteria
- Used for identification of bacteria
according to their biochemical and
physiological properties
Culture – growth of bacteria/microorganisms
obtained in a culture medium
Types of Culture Media according to
CONSISTENCY:
1. Liquid media
- Used for growth of pure batch
cultures (e.g. Enriched media)
2. Semi-Solid
- Used for biochemical/motility
testing
3. Solid Media
- Used widely for the isolation of
pure cultures, for estimating viable
bacterial populations, and a variety
of other purposes; can be
converted to liquid or cannot be
liquefied (rice grains, meat media,
potato slices)
- (eg Enrichment media)
4. Agar
- Gelling agent for solid or semisolid
medium; red algae
- Unique physical properties (melts at
100°C and remains liquid until
cooled to 40°C, the temperature
which it gels)
Types of Culture Media according to
COMPOSITION:
1. Synthetic (Chemically-defined) medium
2. Non-synthetic (Complex; not chemically
defined) medium
Types of Culture Media according to
FUNCTION/PURPOSE:
1. General purpose
- Supports most non-fastidious
bacteria. These media are generally
used for the primary isolation of
microorganisms
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Galope, Sharcele Rovi S.
BMLS 3C
PRELIMS #5
2. Enriched
- Addition of extra nutrients in the
form of blood, serum, egg yolk
(etc.) to basal medium makes them
enriched media to grow
nutritionally exacting (fastidious)
organisms
3. Selective
- These media favor the growth of a
particular bacterium by inhibiting
the growth of undesired bacteria
and allowing growth of desirable
bacteria
4. Differential
- Differential media allow the growth
of more than one microorganism of
interest but with morphologically
distinguishable colonies (color)
- MacConkey Agar differentiates
Lactose Fermenter (pink) to NonLactose Fermenter (creamy)
- Blood Agar (alphahemolitic and
betahemolitic)
5. Anaerobic
- Special media for anaerobic
microorganisms with low oxygen
content, reduced oxidation
6. Specimen transport
- These media are used when
specimen cannot be cultured soon
after coollection
7. Assay
- Used for the assay of vitamins,
amino acids and antibiotics
- Classified as SENSITIVE (zone of
inhibition >10nm and RESISTANT
(small ZoI)
8. Enumeration
- Count the number of colonies
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