Download Controlling-microbial

Unit 1 – Living Cells
• Topic 2 – Microbes!
1. Types of Microbes
2. Controlling the growth of microbes
3. Microbes in industry
Controlling the growth of
microbes
LEARNING OUTCOMES
• Name 2 characteristics about how
microbes grow and reproduce
• State what antibiotics do
• State what antifungals do
• State what antivirals do
Think / Pair / Share
• You have seen microbes grow on agar dishes
• These dishes have now been destroyed
• What would happen to the microbes if we left
them in the incubator?
• Why do you think we should control how
microbes grow?
• How do you think we can do control the growth
of microbes?
Microbial Growth
• Microbes, such as bacteria and yeast,
have many characteristics that help
them to reproduce, such as being able
to reproduce asexually and grow rapidly.
• http://www.youtube.com/watch?v=gEwz
DydciWc
Controlling the growth of
Microbes 1
• Microbes need a suitable temperature
to reproduce.
• Placing microbes in cold temperatures
(fridge) slow down the growth of
microbes.
• Placing microbes in very hot
temperatures (oven) can destroy
microbes.
Controlling the growth of
Microbes 2
Special chemicals can be used to PREVENT the
microbes from growing any further.
These chemicals can be found in:
• cleaning products such as bleach or
disinfectant or
• in medicinal products like:
– AntiBiotics are used to treat Bacterial infections
(bacteria)
– AntiVirals are used to treat Viral infections
(viruses)
– AntiFungals are used to treat Fungal infections
(fungi)
Alexander Fleming (1881 –1955)
• The Discovery of Penicillin and
Antibiotics VIDEO (2.20 mins)
• http://www.youtube.com/watch?v=tMPY
-zf8X94
Alexander Fleming (1881 –1955)
• Alexander Fleming
accidentally discovered
penicillin (an antibiotic)
• He was throwing out old
mouldy bacterial cultures
when he noticed that they
had clear areas around the
mould
• He concluded that the mould
was secreting a chemical
that was killing the bacteria
• He isolated the chemical
• The mould was called
Penicillium so he called the
substance penicillin
• Fleming’s discovery led
to the discovery of many
similar substances
– we now call them
antibiotics.
Antibiotic Disk
• Bacteria can be
grown all over
nutrient agar in a
petri dish
• Then an antibiotic
can be added.
Antibiotics stop
bacteria from
growing.
Antibiotic
NO bacteria growing
Bacteria growing
Clear
zone
(NO
bacteria
growing)
Bacteria
growing
Diameter of
clear zone
Antibiotic Multi-disks
• We can use SEVERAL antibiotics to see
which one is more effective at stopping
the growth of bacteria.
Antibiotic Multi-disks
Aim: To investigate… Which antibiotic is more
effective at stopping the
growth of bacteria
Measurements to be made: The diameter of
the clear zone,
in cm,
using a ruler
Antibiotic Multi-disks
Results:
Conclusion:
(answer your aim and link in your results)
Antibiotic Multi-disks
Results:
Antibiotic Diameter of CLEAR
ZONE (cm)
P
0
S
TE
C
E
G
Conclusion:
0
Antibiotic ____ was the most effective
at stopping the growth of the bacteria
because it had the ______ clear zone.
Controlling the growth of
microbes
LEARNING OUTCOMES
• Name 2 characteristics about how
microbes grow and reproduce
• State what antibiotics do
• State what antifungals do
• State what antivirals do
Controlling the growth of
microbes
LEARNING OUTCOMES
• Explain what is meant by ‘resistant’
bacteria
• Explain what is meant by ‘sensitive’
bacteria
Resistant Vs Sensitive bacteria
Region of bacterial growth
(Bacteria is resistant here)
Region of no bacterial growth
(Bacteria is sensitive here)
• Not all antibiotics are
as effective as each
other.
• What is the best
antibiotic?
• What are the worst
antibiotics?
• ‘best’ and ‘worst’ are
not scientific terms.
• Instead we can use
‘resistant’ and
‘sensitive’
Resistant Vs Sensitive bacteria
• If bacteria is prevented from growing it
is said to be sensitive to the antibiotic
• And if the bacteria is not affected it is
said to resistant to the antibiotic.
• From the antibiotic multi disk diagram,
– the bacteria is resistant to antibiotics
_______
P and E
– And the bacteria is sensitive to antibiotics
_______
G, S, C and TE
Resistant Bacteria
• Resistant bacteria are not killed by
antibiotics.
• This is because the bacteria are too
‘strong’ to be destroyed.
• More and more bacteria are becoming
resistant to antibiotics.
• The main reason is because we over-use
them!
Antibiotics / destroyed / resistant / over-use
Controlling the growth of
microbes
LEARNING OUTCOMES
• Explain what is meant by ‘resistant’
bacteria
• Explain what is meant by ‘sensitive’
bacteria