Lab procedures when Lab procedures when handling micro-organismshandling micro-organisms
Distribution of micro-Distribution of micro-organisms in natureorganisms in nature
Learning ObjectivesLearning Objectives
Discuss the distribution of bacteria Discuss the distribution of bacteria and fungi in natureand fungi in nature
Discuss and outline the Laboratory Discuss and outline the Laboratory Procedures for Micro-organismsProcedures for Micro-organisms
State precautions used when State precautions used when working with micro-organismsworking with micro-organisms
Define the terms: Asepsis & SterilityDefine the terms: Asepsis & Sterility Outline containment & disposal Outline containment & disposal
methods in relation to microbesmethods in relation to microbes
Micro-organismsMicro-organisms Can only be seen with the help of a Can only be seen with the help of a
microscopemicroscope Include bacteria, some fungi (yeast) and Include bacteria, some fungi (yeast) and
some protists (plankton)some protists (plankton) Occupy a wide range of habitats e.g. salt Occupy a wide range of habitats e.g. salt
water, fresh water, soil, dust, air, hot water, fresh water, soil, dust, air, hot springs etc.springs etc.
Fungi are mostly terrestrialFungi are mostly terrestrial Bacteria can be found in extreme Bacteria can be found in extreme
environments from the inside of environments from the inside of volcanoes to inside the human gutvolcanoes to inside the human gut
Laboratory procedures when Laboratory procedures when handling micro-organismshandling micro-organisms
• 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
Vocabulary
Learning CheckLearning Check
Name 3 types of Micro organismsName 3 types of Micro organisms How can you view bacteria in the How can you view bacteria in the
laboratory?laboratory? What does the term asepsis mean?What does the term asepsis mean? What does the term sterile mean?What does the term sterile mean?
Growth of micro-organisms
• Under suitable conditions one micro-organism 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 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
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-
organismsSeal all plates once inoculated.
Precautions that can be taken when handling micro-
organismsLabel all plates once prepared.
Learning CheckLearning Check
List four precautions that should be List four precautions that should be taken when working with micro-taken when working with micro-organismsorganisms
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.
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.
Examine the plate and record the results.
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
Growth
Yeasts and moulds grow best at 25 - 30°C.
Bacteria generally require 35°C.
Examine the plate and record the results
ColoniesColonies 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:
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 CheckLearning Check
What growth medium is used for What growth medium is used for micro-organisms?micro-organisms?
How do you inoculate a loop?How do you inoculate a loop? How do you transfer the substance to How do you transfer the substance to
be grown onto the agar plate?be grown onto the agar plate? What temperature should the agar What temperature should the agar
plates be incubated at?plates be incubated at? How should plates be disposed of?How should plates be disposed of?
Syllabus: What you need to Syllabus: What you need to knowknow
Precautions when working with Precautions when working with micro-organisms.micro-organisms.
Asepsis and sterility: definition of Asepsis and sterility: definition of each term as applied to living each term as applied to living organisms.organisms.
Containment and disposal.Containment and disposal.