1. Lab procedures when handling micro-organisms
Distribution of micro-organisms in nature

2. Learning Objectives
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

3. Micro-organisms 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

4. Laboratory procedures when handling micro-organisms

5. 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

6. Vocabulary Inoculation is the addition of cells to the nutrient medium
Incubation is the growing of the microbes in a warm environment

7. Learning Check 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?

8. 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.

9. 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.

10. Precautions that can be taken when handling micro-organisms
Wash hands before and after the experiment.

11. Precautions that can be taken when handling micro-organisms
Wash the bench with disinfectant before and after the experiment.

12. 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

13. 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

14. 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.

15. 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.

16. Precautions that can be taken when handling micro-organisms
Open all containers for the shortest possible time.
Open lids the shortest possible distance.

17. Precautions that can be taken when handling micro-organisms
Seal all plates once inoculated.

18. Precautions that can be taken when handling micro-organisms
Label all plates once prepared.

19. Learning Check
List four precautions that should be taken when working with micro-organisms

20. How to grow a culture.

21. Take a sterile agar plate.
Flame an inoculating loop to sterilise it.
Dip the loop into sterile water or alcohol to cool it.

22. 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.

23. Sterilise the loop again by flaming it.
While only slightly opening the agar plate streak the inoculating loop across the surface of the agar.
Sterilise the loop again by flaming it.

24. Label and seal the petri-dish and incubate it upside down for 2 - 3 days.
Examine the plate and record the results.

25. Growth
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

26. Yeasts and moulds grow best at 25 - 30°C.
Bacteria generally require 35°C.

27. Examine the plate and record the results

28. Colonies
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

29. 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.

30. Learning Check What growth medium is used for micro-organisms?
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?

31. Syllabus: What you need to know
Precautions when working with micro-organisms.
Asepsis and sterility: definition of each term as applied to living organisms.
Containment and disposal.