Transcript File - Sydney russell school e

B1 L1
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.
Why is it important to use aseptic techniques when growing or dealing with
micro-organisms?
THINK, PAIR, SHARE
Success Criteria
At the end of this lesson it will be:
Best
Better
Good
Explain why you need uncontaminated
microorganism cultures to study the
effects of different treatments
Describe how apparatus is sterilised and how
this achieves pure cultures
Able to state what aseptic technique is?
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.
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 Petri dish is flat to
give the microbe plenty of
surface to grow on.
The lid stops unknown
microbes dropping onto the
agar and contaminating the
culture.
How do the Petri dish and incubator provide the best
conditions for microbes to grow?
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.
Temperature
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.
Learning objective check
Good
State what is needed to grow bacteria
Aseptic Technique
Collect a handout
………………….. 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
uncontaminated
air
incubated
Petri dish
rapid
pathogens 25°C sterilised
Why keep things sterile?
What 3 diseases does MMR vaccine
protect from?
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?
.
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.
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.
The task for today.
Growing bacteria in the laboratory
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
The task for today.
Practical
Growing Microbes safely in the laboratory.
Today you will describe how to grow microorganisms 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.
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
Aseptic Technique:
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.
Flame the mouth of the bottle for 2 or 3
seconds.
Pass the inoculating loop through the flame
until red hot.
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.
Lift the lid of the Petri dish just enough to allow
entry of the inoculating loop.
Incubate at around 25oC (cultures should not
be cultured at 37oC as this is an ideal
temperature for the growth of many
pathogenic species.)
Do not open the Petri dish after incubation.