Transcript 3.1.5 Handling Microorganisms File

Lab procedures when handling
micro-organisms
Distribution of micro-organisms in
nature
Learning Objectives
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Discuss the distribution of bacteria and
fungi in nature
Discuss and outline the Laboratory
Procedures for Micro-organisms
State precautions used when working
with micro-organisms
Define the terms: Asepsis & Sterility
Outline containment & disposal methods
in relation to microbes
Micro-organisms
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Can only be seen with the help of a
microscope
Include bacteria, some fungi (yeast) and some
protists (plankton)
Occupy a wide range of habitats e.g. salt
water, fresh water, soil, dust, air, hot springs
etc.
Fungi are mostly terrestrial
Bacteria can be found in extreme
environments from the inside of volcanoes to
inside the human gut
Laboratory procedures when
handling micro-organisms
Vocabulary
• Asepsis means that measures are taken
to exclude unwanted organisms
• Sterile means that all micro-organisms
are destroyed i.e. there is nothing living
Vocabulary
Inoculation is the addition of cells to the
nutrient medium
Incubation is the growing of the microbes
in a warm environment
Learning Check
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Name 3 types of Micro organisms
How can you view bacteria in the laboratory?
What does the term asepsis mean?
What does the term sterile mean?
Growth of micro-organisms
• Under suitable conditions one microorganism can be grown into a colony of
micro-organisms which is visible to the
naked eye.
• Micro-organisms are grown on a special
medium containing a food supply, most
commonly nutrient agar.
Growth of micro-organisms
• The procedures involved require caution as
the micro-organism to be grown (or any
contaminating micro-organism, if present)
may be a disease causing microbe.
• As a result certain precautions are taken
when handling micro-organisms to reduce
the possibility of contamination and to
prevent the growth of undesirable microorganisms.
Precautions that can be taken
when handling micro-organisms
Wash hands before and after the experiment.
Precautions that can be taken
when handling micro-organisms
Wash the bench with disinfectant
before and after the experiment.
Precautions that can be taken
when handling micro-organisms
Sterilise all equipment before and after use.
This can be done by placing all equipment:
• In an autoclave (or pressure cooker) at
120°C for 15 minutes
• in Dettol for 24 hours
Precautions that can be taken
when handling micro-organisms
After an experiment material can be
placed in a dustbin only after
sterilisation
Sterilised equipment can be reused
Precautions that can be taken
when handling micro-organisms
Flame all needles, loops and necks of
test-tubes by heating them in the flame
of a Bunsen burner.
Precautions that can be taken
when handling micro-organisms
• Turn off the
Bunsen burner
when not in use or
make sure that the
flame is visible.
Precautions that can be taken
when handling micro-organisms
• Open all containers
for the shortest
possible time.
• Open lids the
shortest possible
distance.
Precautions that can be taken
when handling micro-organisms
Seal all plates once inoculated.
Precautions that can be taken
when handling micro-organisms
Label all plates once prepared.
Learning Check
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List four precautions that should be taken
when working with micro-organisms
How to grow a culture.
• Take a sterile agar
plate.
 Flame an
inoculating loop to
sterilise it.
 Dip the loop into
sterile water or
alcohol to cool it.
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Flame the neck of the container from
which the sample is to be taken.
Inoculate the loop by placing it briefly into
the sample to be grown.
Re-flame the neck of the container.
While only slightly opening the agar plate
streak the inoculating loop across the
surface of the agar.
Sterilise the loop again by flaming it.
• Label and seal the
petri-dish and
incubate it upside
down for 2 - 3
days.
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Examine the plate
and record the
results.
Growth
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Once the plates are sealed
and labelled turn them upside
down and place them in an
oven (incubator) to allow any
bacteria and fungi to grow.
Placing them upside down
reduces problems due to
condensation
Yeasts and moulds grow best at 25 - 30°C.
Bacteria generally require 35°C.
Examine the plate and record the results
Colonies
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Bacterial colonies
are usually seen as
white, cream or
yellow shiny dots
Fungal colonies
appear as a
powder or as a
fuzzy growth,
similar to cotton
wool in appearance
Disposal
All micro-organisms should be destroyed
after use by sterilising all petri-dishes and
equipment:
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by placing them in an autoclave (or
pressure cooker) at 120°C for 15 minutes
or by placing them in Dettol for 24 hours.
Learning Check
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What growth medium is used for microorganisms?
How do you inoculate a loop?
How do you transfer the substance to be
grown onto the agar plate?
What temperature should the agar plates
be incubated at?
How should plates be disposed of?
Syllabus: What you need to
know
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Precautions when working with microorganisms.
Asepsis and sterility: definition of each
term as applied to living organisms.
Containment and disposal.