Microorganisms
and Disease
Chapter 1
Lesson 5
Microorganisms
• Microorganisms are organisms that are
microscopic, or too small to be seen with just
the eyes.
• They can be unicellular or multicellular.
• Microorganisms are EVERYWHERE!!! They are
in food that you eat, on your books, and inside
your body.
Microorganisms are helpful.
• They provide larger organisms with some of
the food and oxygen they need to survive.
• They also enrich the environment by breaking
down dead organisms.
Microorganisms can be harmful.
• A disease is anything that interferes with the
normal functions of the body.
• Some diseases are caused by harmful
materials in the environment, but many are
caused by microscopic agents. These agents
are called pathogens.
• Some types of bacteria, viruses, protists, and
fungi can cause diseases.
Infectious Diseases
• Diseases caused by pathogens that can be
passed from one organism to another are
called infectious diseases.
• Pathogens can be transmitted from direct
contact with an infected individual. They also
can be transmitted through the air if a person
touches a contaminated object.
• Animals can pass pathogens to people.
Have you ever had a sore throat and
gone to the doctor?
• What did the doctor do to check your
throat?
• Your doctor probably used a cotton swab
and rubbed it on the back of your throat.
They do this to pick up some bacteria from
your throat.
• This is called a throat culture. They place
the sample from the cotton swab on a
special plate and see if a bacterium grows.
This bacterium is called Streptococcus. It
attacks cells in the throat and causes a
disease we call strep throat.
Harmful Bacteria
• Some bacteria cause
disease by producing
poisonous substances called
toxins.
• Tetanus and scarlet fever
are examples of diseases
caused by toxins.
Bacteria can live on food.
• It can live on uncooked meats, raw eggs, and
other foods.
• Examples of these bacteria are E.coli and
Salmonella. They both attack the digestive
system by damaging cells in the intestines and
stomach.
Lyme disease
• This is also caused by bacteria.
• The bacteria can enter a person’s body when
he or she is bitten by a tick that carries it.
Harmful Fungi
• Have you ever had or heard of athlete’s foot?
This is caused by a fungus that is found in
damp places and lives on skin. It can cause
flaky skin and itching.
Harmful Protists
• Dysentery is a disease caused by a protist. It is
spread by amoebas that enter an organism’s body
by contaminated food or water.
• Sleeping sickness is also caused by a protist. This
protist lives in the bodies of cows and other
animals. Flies can transfer the protist to humans.
• Malaria is a disease caused by mosquitoes that
transmit the protist that causes malaria form one
person to another. Once it’s inside the body, the
protist reproduces in the person’s red blood cells
and destroys them.
Microorganisms can harm plants.
• In the 19th century, a protist spread
throughout Ireleand and destroyed large
amounts of potato crops. The disease caused
by the protist is known as potato blight.
Protecting ourselves from harmful
microorganisms
Famous Scientists:
• Louis Pasteur- developed a process
to eliminate microbes from some
foods. This process heats liquids,
such as milk, to high temperatures
and the heat destroys bacteria
without significantly altering the
liquid. This process is known as
pasteurization.
• Cooking food also destroys many
harmful bacteria.
Famous Scientists
• Alexander FlemingDiscovered the first antibiotic,
penicillin in 1928.
• Antibiotics are chemicals
used to treat bacterial
infections. They stop the
growth of bacteria.
• Today we have many different
antibiotics. Each one works
for only certain types of
bacteria.
Famous Scientists
• Edward Jenner- Created the
first vaccine in 1796. It was
used to treat smallpox.
• Jonas Salk- Created a vaccine to
prevent a viral disease caused
polio in the 1950s.
• A vaccine is made from dead or
weakened pathogens. Vaccines
can prevent you from getting
certain diseases.
What is the best way to stop the
spread of most infectious diseases?
• Just WASH your HANDS! This simple act can
remove the pathogens you might pick up and
help prevent the spread of diseases. So wash
up!!!
What are some common
microorganisms?
• Bacteria
• Some fungi
• Some protists
Why are microorganisms important?
• Microscopic organisms provide larger
organisms, including people, with some of the
food and oxygen they need to survive. Some
microscopic organisms enrich the
environments by breaking down dead
organisms.
Are microorganisms unicellular or
multicellular?
• Microorganisms include
unicellular and multicellular
organisms.
What are some examples of unicellular
protists and fungi?
• Unicellular protists- amoeba, paramecium,
Euglena
• Unicellular fungi- yeast
What would happen if microorganisms
disappeared from Earth?
• If microorganisms disappeared from Earth,
many larger organisms would be without a
food source. Nutrients would not be recycled
through an environment.
Think about a time when you have been sick.
What might have caused you to get sick?
Where do bacteria that cause a form of
pneumonia attack the body?
• The lungs
• How are diseases such as tetanus or
scarlet fever caused?
• By bacteria that produce poisonous
substances called toxins
What kinds of bacteria can attack the digestive
system after someone was in contact with
uncooked food?
• E. coli and salmonella
What diseases are caused by harmful
fungi?
• Athlete’s foot
• How are the microorganisms that destroyed
potato crops throughout Ireland in the
nineteenth century similar to the ones that cause
malaria?
• They are similar because they are both protists.
• Where do protists that cause malaria reproduce?
• Inside red blood cells
• During what time of year do the
number of Lyme disease cases
increase?
• summer
How are diseases spread?
• Some diseases are caused by organisms, such
as some bacteria. Disease can also be spread
when a healthy individual comes in contact
with an individual who is sick. Some disease
occur when people eat uncooked food.
Animals can also spread disease.
Why is the term agent more accurate than
organism when defining a pathogen?
• Organisms are living things. Viruses are not
living. Because viruses can cause disease, it is
more accurate to use the term agent instead
of organism when defining a pathogen.
• Why do scientists develop
different antibiotics?
• Not all antibiotics work on all
bacteria, so scientists are
continually trying to find new
antibiotics that will work on
different types of bacteria.
How does the process of pasteurization
help keep us safe from disease?
• Pasteurization destroys harmful
bacteria found in foods such as
milk.
Look closely at the word antibiotic.
• What is the prefix?
• anti- this means “opposed to” or “against”
• The word biotic relates to life or living
organisms.
• Antibiotics inhibit the growth of
living microorganisms like bacteria.
Vaccines
• Vaccines contain pathogens that have been
killed so that they are not longer harmful. The
vaccines help prevent disease by “training”
the body’s defenses to attack specific
pathogens.
What are some ways to prevent the
spread of infectious diseases?
• Washing your hands
• Getting vaccinations
Antibiotics kill certain bacteria. Why
don’t they kill all bacteria?
• There are many different types of bacteria.
Because not all bacteria are the same,
different chemicals are needed to kill bacteria.