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.