1. Unit 7: Microbes & Diseases
8.L1.1 Summarize the basic characteristics of viruses, bacteria, fungi, and parasites relating to the spread, treatment, and prevention of disease.

2. 8C Microbes and Disease What are microbes? Uses of microbes
Contents
8C Microbes and Disease
What are microbes?
Uses of microbes
How microbes cause disease
Fighting disease
Summary activities

3. What are microbes?
Microbes are very small living things and are sometimes called
micro-organisms.
Microbes are so tiny that they cannot be seen with the naked eye. They can only be seen using a microscope.
How many different microbes can you name?

4. Different types of microbes
There are three types of microbes:
microbes
bacteria
viruses
fungi

5. Bacteria fact file
Bacteria Found everywhere, in the air, soil, water, inside your body and on your skin. e.g. Salmonella and Streptococcus
size: 1/1000 mm very small
shape: Bacteria can be spherical, rod-shaped or spiral or corkscrew. Usually classified by its shape.
structure: Bacteria are single-celled organisms, which do not completely have a nucleus.
Some cause disease, but many
are useful.
reproduction: Bacteria reproduce very quickly. They tend to multiply very rapidly under favourable conditions, forming colonies of millions or even billions of organisms within a space as small as a drop of water.

6. Bacterium structure

7. Viruses fact file
Viruses MUST HAVE A HOST CELL e.g. flu virus and HIV (the AIDS virus), chicken pox, viral meningitis, Ebola.
size: 1/1,000,000 mm
shape: Viruses have regular and geometric shapes.
structure: A virus is a simple organism which does not display ALL the characteristics of living things. They are made up of a protein coating and some genetic material.
reproduction: Viruses can only grow and reproduce within other living things.

8. Virus structure

9. Fungi fact file Fungi e.g. Penicillium and yeast
size: Some fungi can actually be seen with the naked eye, others are slightly bigger than bacterial cells.
shape: Fungi come in many different shapes.
structure: Fungi have the
most complex structures of
all the microbes. They feed
off other living things.

10. Fungi (yeast) structure

11. 8C Microbes and Disease What are microbes? Uses of microbes
Contents
8C Microbes and Disease
What are microbes?
Uses of microbes
How microbes cause disease
Fighting disease
Summary activities

12. 8C Microbes and Disease What are microbes? Uses of microbes
Contents
8C Microbes and Disease
What are microbes?
Uses of microbes
How microbes cause disease
Fighting disease
Summary activities

13. Microbes can cause disease
The diseases caused by microbes and their severity depend on the type of microbe.
viruses
bacteria
fungi
influenza (flu)
food poisoning
fungal sinusitis
mumps
sore throats
athlete’s foot
chickenpox
tuberculosis (TB)
Onychomycosis
(causes discoloured toe nails)
smallpox
tetanus
polio
cholera
rabies
typhoid
German measles
whooping cough
viral
meningitis
bacterial
meningitis

14. Which type of microbe?

15. How do microbes enter the body?
Microbes can enter the body in many different places.
eyes
ears
nose
mouth
skin
genitals
cuts
How are the diseases caused by microbes spread?

16. How are microbes spread?
The spreading of microbes and disease is known as transmission.
A cough or a sneeze can release millions of microbes into the air which can then infect somebody else.
1. Transmission by air
Dirty water can transmit many diseases, e.g. cholera, which can be transmitted by drinking.
2. Transmission by water

17. How are microbes spread?
An animal can carry a microbe from one place to another, e.g. a mosquito which spreads the malaria parasite.
3. Transmission by animals
Many microbes can be exchanged from one person to another by direct or indirect contact:
4. Transmission by contact
direct contact by hand;
indirect contact, e.g. by walking on a
wet floor already contaminated by
someone else who has athlete’s foot;
sexual contact.

18. How are microbes spread?
There are other forms of indirect contact, e.g. the transmission of microbes from mother to unborn child.
4. Transmission by contact
If the mother develops the HIV/Aids infection, it can be passed on to the unborn child through the placenta.
Transmission through the placenta
Transmission via breastfeeding
If a child is being breastfed, he or she can also pick up microbes from the mother via the mother’s milk.

19. How is the spread of disease stopped?
The spread of disease can be prevented by making sure that good hygiene is used in key places such as bathrooms and kitchens.
Chemicals called antibiotics can be used to treat bacterial infections.
People can be immunized against some diseases (viruses) by the injection of a vaccine.

20. 8C Microbes and Disease What are microbes? Uses of microbes
Contents
8C Microbes and Disease
What are microbes?
Uses of microbes
How microbes cause disease
Fighting disease
Summary activities

21. Fighting microbes
How does the body fight off microbes that cause disease?

22. What do white blood cells do?
The human body has a number of natural defences against microbes. Noses are hairy inside to trap microbes!
white blood cell
The body also produces white blood cells to help defend it from microbes.
Some white blood cells can destroy microbes by engulfing them.
antigen
antibody
Some white blood cells are able to produce chemicals called antibodies. These pairing with matching antigens on the surfaces of microbes and so help the white blood cells to engulf microbes.

23. 8C Microbes and Disease What are microbes? Uses of microbes
Contents
8C Microbes and Disease
What are microbes?
Uses of microbes
How microbes cause disease
Fighting disease
Summary activities

24. Glossary
antibiotics – Chemicals prescribed as medicine to kill bacteria inside the body.
antibodies – Chemicals produced by white blood cells to fight microbes that cause disease.
bacteria – The type of microbes that are single-celled organisms.
fungi – The type of microbes that feed off other living things.
immune – Resistance to infection caused by a microbe.
microbe – A very small living thing.
transmission – The spread of a disease from person to person.
viruses – The type of microbes that can only grow and reproduce within other living things.