1. 4/18/2013
Microorganisms are kept for:
Control the culture media (testing
media).
Control the biochemical &
sensitivity testing.
For teaching purpose.
For further identification.
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2. 4/18/2013
The bacteria are vary in their ability
to remain a life after they complete
their growth. There are different
methods for preservation of
microorganisms:
Moist storage.
Cold storage.
Dry storage.
Freeze drying storage (The best one).
In this method keep the organisms
by serial subculture (interval time)
to keep it is life.
Use different types of media
according to the type of
microorganisms
Choice media with low nutritional
substances.
Semi-solid media (Nutrient agar).
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3. 4/18/2013
Cooked meat media (CMM).
Blood broth.
Dorset egg.
Egg saline.
Skimmed milk.
Semi-solid media:
Staphylococci: Subculture every 1-2 month.
Enterobacterieace: Subculture every 3
month.
Blood broth:
Streptococci: all of them except
pneumococci every one month.
Dorset egg, Egg saline & skimmed
milk:
Used for many organisms at least every 6
month subculture.
CMM:
Clostriia: subculture every 6-12month.
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4. 4/18/2013
Method:
Use screw capped container.
After inoculation (stabbing), incubate
over night.
Sealing by paraffin wax – fill the
container.
Make at least duplicate every organism.
Advantage:
Easy.
Practical.
Disadvantage:
Cannot prevent mutation.
There is chance for drying &
contamination.
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5. 4/18/2013
Use low temperature for
preservation the microorganisms.
Use different degree of temperature:
4 - 8 C° domestic refrigerator.
-20 C° - -40 C° deep freezer.
-70 C° - -80 C° ultra deep freezer.
-70 C° solid CO2 (Micro-bank methods).
-196 C° liquid nitrogen methods.
Some organisms like Niesseria and H.
influenzae cannot preserve by this method.
4 - 8 C° or -20 C° - -40 C° keep the organisms
for short time.
-70 C° culture the organism in tube and then
inserted in container CO2.
Adv. : keep organism for long time – no change
and no need for subculture.
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6. 4/18/2013
Disadv. : expensive – regular filling with
CO2.
-80 C° ultra deep freezer:
When used it need certain precautions to
avoid ice crystals and concentration of
salt (destroy the organisms) by using:
Glycerol – Sugar – Dimethyl sulphoxide
(DMSO).
-196 C° (liquid nitrogen):
Rapid freezing and rapid rewarming will
avoid formation of ice crystal, and viability
does not affected.
Disadv: have some disadvantage of
CO2.
Micro-bank system:
Commercial supplied cryovials which
are screw capped 2ml container.
Method: Bacterial suspension add to
the vial which contain
cryopreservative. The organism
absorbed by the glass beads in the vial,
the excess fluid is absorbed and
discarde (storge at -70 C°).
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7. 4/18/2013
Done by several method:
Filter paper disc methods: Thick
suspension of organism is prepared,
and impregnate the disc of filter paper
with it. Drying take place in a desiccant
under vacuum, over reducing
substance such as phosphorus peroxide
(P2O5), and lastly impregnated with
paraffin oil.
Slamp method: Similar to previous
method
with some modification in the
reducing substance which is
incorporated in the medium (10%
gelatin with ascorbic acid – paper is
impregnated with the paraffin oil
before the culture – dry as describe
above).
L. method (La page method):
Drying in bottle or prefer tubes or
capillary tube seal it and kept for long
time.
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