1. L8 – Keeping things sterile
B1 L1
L8 – Keeping things sterile
Learning Objective
To be able to explain the processes used to keep things sterile
Key words: Agar, culture medium,
Starter activity:
For bacterial Infections - Use Antibiotics
For viruses – Don’t use Antibiotics because they do not work against them so it is left alone for the body to deal with.

2. Starter
Why is it important to use aseptic techniques when growing or dealing with micro-organisms?
THINK, PAIR, SHARE

3. Best Better Good Success Criteria
At the end of this lesson it will be:
Explain why you need uncontaminated microorganism cultures to study the effects of different treatments
Best
Describe how apparatus is sterilised and how this achieves pure cultures
Better
Able to state what aseptic technique is?
Good

4. How do we grow bacteria and fungi cultures?
Like all living organism, bacteria and fungi need nutrients, these are supplied using an Agar gel.
The agar gel is melted and then poured into glass petri dishes and allowed to set.

5. Agar plates and Petri dishes
Agar is a jelly containing a mixture of nutrients to help the microbe to grow known as a culture medium.
Petri dishes can be kept in incubators which help the microbes to grow.
The lid stops unknown microbes dropping onto the agar and contaminating the culture.
The Petri dish is flat to give the microbe plenty of surface to grow on.
How do the Petri dish and incubator provide the best conditions for microbes to grow?

6. Colonies and Agar Jelly
Individual microbes are difficult to see without a microscope. However, if provided with enough FOOD, WARMTH and OXYGEN (although some can live without it), they will rapidly divide to produce a COLONY.
This is clearly visible to the naked eye.
* We usually grow microbes in special dishes called PETRI DISHES which allow air to pass freely in and out but exclude foreign organisms and their spores.
* We put a jelly-like material called AGAR JELLY in the dishes. The jelly contains food for the microbes.
* All the equipment must be sterilized (heated to a high temperature) to kill any microbes that may already be there.

7. As pathogens grow much worse at lower temperatures
In school and college laboratories, cultures should be incubated at a maximum temperature of 25 °C,
As pathogens grow much worse at lower temperatures
Keeping the temperature at a maximum of 25 degrees greatly reduces the likelihood of growth of pathogens that might be harmful to humans.

8. Learning objective check
Good
State what is needed to grow bacteria

9. Collect a handout Aseptic Technique
………………….. cultures of microorganism are required for investigating the action of disinfectants and antibiotics.
For this:
- Petri dishes and culture media must be ……………… before use to kill unwanted microorganisms
- inoculating loops used to transfer ………………… to the media must be sterilised by passing them through a ………..
- the lid of the ………. ………. should be sealed with adhesive tape to prevent microorganisms from the ……… contaminating the culture.
In school and college laboratories, cultures should be …………………… at a maximum temperature of …………… which greatly reduces the likelihood of growth of ……………….. that might be harmful to humans. In industrial conditions higher temperatures can produce more ………… growth.
Missing words: micro-organisms flame Petri dish pathogens 25°C sterilised uncontaminated air incubated rapid

10. Why keep things sterile?

12. Keeping things sterile The Nervous system
What 3 diseases does MMR vaccine protect from?
Keeping
things sterile
What is a sterile culture. .
Give 2 reasons it is important to keep cultures sterile. .
What temperature should we incubate cultures at in school and why? How does this compare to industry? .
The Nervous
system

13. RULES!
Never leave a culture dish open, even for a short time when viewing colonies of organisms, unless you intend to destroy it.
When it is necessary to open a dish, keep the lid close to the dish, open it only as far and as long as is necessary to accomplish the procedure, and keep the lid between your face (and your germs!) and the agar surface.

14. Self Assessment Before we begin the practical, have you;
described how to grow micro-organisms safely in your book.
explained precautions needed when handling microorganisms and growing them safely.

15. Growing bacteria in the laboratory
The task for today.
Growing bacteria in the laboratory

16. Practical: Growing Bacteria Draw your plate.
You can either follow the instructions on your worksheet, and draw a zig zag on your agar plate, or you can try the streaking method shown in the video.
Remember:
Sellotape lid to the base so it cannot come off
Incubate plate for at least 48 hours
Examine growth of bacteria

17. Growing Microbes safely in the laboratory.
The task for today.
Practical
Growing Microbes safely in the laboratory.
Today you will describe how to grow micro-organisms safely in your book. You will then carry out a practical to grow micro-organisms found in the classroom. You will draw your plate and label it carefully.

18. Growing bacteria in the laboratory
The task for today.
Growing bacteria in the laboratory
Harmless bacteria can be grown in the laboratory on agar jelly
The agar gives the bacteria food and water
The plates containing the agar jelly have to be sterile – that means ‘germ-free’
The plates are then incubated to make the bacteria GROW

19. Aseptic Technique:
Secure the lid with adhesive tape. Use two pieces to fasten the lid, but do not seal all the way round (this could create anaerobic conditions and encourage the growth of possible pathogenic microbes.
CORRECT HANDLING TECHNIQUES
Grasp the culture bottle in one hand; remove the cap with the little finger of the other hand – do not place the cap on the work surface.
Lift the lid of the Petri dish just enough to allow entry of the inoculating loop.
Flame the mouth of the bottle for 2 or 3 seconds.
Incubate at around 25oC (cultures should not be cultured at 37oC as this is an ideal temperature for the growth of many pathogenic species.)
Pass the inoculating loop through the flame until red hot.
Do not open the Petri dish after incubation.