Complete Unit 17 CD Assignment
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Najah Bendriss BTEC Applied Science Biology Unit 17CD
Culturing microorganisms
P4: Preparation, inoculation and measurement of microbial growth using aseptic
techniques.
Aim:
To prepare the nutrient agar medium, inoculate the bacterial cultures (SPREAD, STREAK
AND POUR PLATE) using aseptic techniques and measure the growth of the bacterial colon-
ies.
Risk Assessment:
Hazard Risk Source of in- Control meas- Emergency pro-
formation ures cedure
Inoculation loop When the in- Handle carefully Wash burned
oculation loop skin under rush-
is heated it can ing cold water
potentially
cause burns.
Pure cultures of If handled in- Follow aseptic Use disinfectant
bacteria correctly can techniques. if bacteria acci-
cause contam- dently get onto
ination. another sur-
face.
Test tubes Glass equip- Handle care- Clean the cut
ment if broken fully. and cover with
can cause cuts a clean water-
that can get in- proof dressing.
fected by the
microorganisms
Apparatus:
Inoculation loop
L-rod
Nutrient Agar
Petri plates
Pasteur pipettes
Pure cultures of bacteria
Test tubes for serial dilution
1
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Najah Bendriss BTEC Applied Science Biology Unit 17CD
Method:
Prepare the suitable growth medium for inoculating the bacterial cultures and autoclave it.
Preparation of Nutrient Agar:
I accurately weighed 2.8 g of nutrient broth and dissolved it in 100 ml of sterile water in a
beaker. I autoclaved it by sterilising at 121ºC for 15 minutes. After this I allowed it to cool
and placed in a water bath maintained at 50ºC.
Preparation of Pour plates
In a pour plate, I added a small amount of inoculum (about 0.5 ml) from a broth culture by
pipette to the centre of a Petri dish. I poured cooled, but still molten, agar medium in a test
tube into the Petri dish. I then rotated the dish gently (first N-S, then NW-SE, then NE-SW),
to ensure that the culture and medium were thoroughly mixed and the medium covered the
plate evenly.
Pour plates allow micro-organisms to grow both on the surface and within the medium.
Most of the colonies grow within the medium and are small in size and may be confluent.
The few colonies that grow on the surface are of the same size and appearance as those on
a streak plate.
These plates could then be used to test the anti-microbial effects of various substances.
Inoculation using a Pasteur pipette
At all times, hold the pipette as still as possible.
1 I loosened the cap of the bottle containing the inoculum (pure culture)
2 I removed the sterile Pasteur pipette from its container, attached the teat and held it in
my right hand.
3 I lifted the test tube containing the inoculum with my left hand.
4 I removed the cap with the little finger of my right hand.
5 I flamed the test tube neck.
6 I squeezed the teat bulb of the pipette very slightly, put the pipette into the test tube and
drew up the required volume of the culture. Do not squeeze the teat bulb of the pipette
after it is in the broth as this could cause bubbles and possibly aerosols.
7 I removed the pipette and flamed the neck of the test tube again. I replaced the cap.
8 I placed the test tube in its rack.
Inoculating the Petri dish
1) I lifted the lid of the Petri dish slightly with my right hand and inserted the pipette
into the Petri dish. Gently, I released the required volume of inoculum onto the
centre of the dish. I replaced the lid.
2
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written by
najbo123
www.stuvia.com
Downloaded by: najbo123 | Want to earn £756
Distribution of this document is illegal extra per year?
, Stuvia.co.uk - The Marketplace for Revision Notes & Study Guides
Najah Bendriss BTEC Applied Science Biology Unit 17CD
Culturing microorganisms
P4: Preparation, inoculation and measurement of microbial growth using aseptic
techniques.
Aim:
To prepare the nutrient agar medium, inoculate the bacterial cultures (SPREAD, STREAK
AND POUR PLATE) using aseptic techniques and measure the growth of the bacterial colon-
ies.
Risk Assessment:
Hazard Risk Source of in- Control meas- Emergency pro-
formation ures cedure
Inoculation loop When the in- Handle carefully Wash burned
oculation loop skin under rush-
is heated it can ing cold water
potentially
cause burns.
Pure cultures of If handled in- Follow aseptic Use disinfectant
bacteria correctly can techniques. if bacteria acci-
cause contam- dently get onto
ination. another sur-
face.
Test tubes Glass equip- Handle care- Clean the cut
ment if broken fully. and cover with
can cause cuts a clean water-
that can get in- proof dressing.
fected by the
microorganisms
Apparatus:
Inoculation loop
L-rod
Nutrient Agar
Petri plates
Pasteur pipettes
Pure cultures of bacteria
Test tubes for serial dilution
1
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Najah Bendriss BTEC Applied Science Biology Unit 17CD
Method:
Prepare the suitable growth medium for inoculating the bacterial cultures and autoclave it.
Preparation of Nutrient Agar:
I accurately weighed 2.8 g of nutrient broth and dissolved it in 100 ml of sterile water in a
beaker. I autoclaved it by sterilising at 121ºC for 15 minutes. After this I allowed it to cool
and placed in a water bath maintained at 50ºC.
Preparation of Pour plates
In a pour plate, I added a small amount of inoculum (about 0.5 ml) from a broth culture by
pipette to the centre of a Petri dish. I poured cooled, but still molten, agar medium in a test
tube into the Petri dish. I then rotated the dish gently (first N-S, then NW-SE, then NE-SW),
to ensure that the culture and medium were thoroughly mixed and the medium covered the
plate evenly.
Pour plates allow micro-organisms to grow both on the surface and within the medium.
Most of the colonies grow within the medium and are small in size and may be confluent.
The few colonies that grow on the surface are of the same size and appearance as those on
a streak plate.
These plates could then be used to test the anti-microbial effects of various substances.
Inoculation using a Pasteur pipette
At all times, hold the pipette as still as possible.
1 I loosened the cap of the bottle containing the inoculum (pure culture)
2 I removed the sterile Pasteur pipette from its container, attached the teat and held it in
my right hand.
3 I lifted the test tube containing the inoculum with my left hand.
4 I removed the cap with the little finger of my right hand.
5 I flamed the test tube neck.
6 I squeezed the teat bulb of the pipette very slightly, put the pipette into the test tube and
drew up the required volume of the culture. Do not squeeze the teat bulb of the pipette
after it is in the broth as this could cause bubbles and possibly aerosols.
7 I removed the pipette and flamed the neck of the test tube again. I replaced the cap.
8 I placed the test tube in its rack.
Inoculating the Petri dish
1) I lifted the lid of the Petri dish slightly with my right hand and inserted the pipette
into the Petri dish. Gently, I released the required volume of inoculum onto the
centre of the dish. I replaced the lid.
2
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