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Microorganisms
Lesson 5
Microorganisms
• What is a Microorganism?
• Microorganisms are tiny creatures, too small
to be seen with just our eyes.
• Microorganisms provide larger organisms with
some of the food and oxygen they need to
survive.
Studying Microscopic Organisms
• A microscope is an instrument that produces
an enlarged image of an object.
• Anton van Leeuwenhoek: Dutch merchant
used a microscope to study organisms in the
1600’s.
• A compound microscope uses two or more
lenses and a light source to magnify objects as
much as 2,000 times.
Studying Microscopic Organisms
• An electron microscope uses a beam of
electrons rather than a light source to magnify
samples.
• Electron microscopes cannot be used on living
samples, because the stream of electrons and
the preparation process would kill them.
How are microorganisms beneficial?
• Microorganisms are decomposers.
• A decomposer is an organism that breaks
down dead materials into simpler substances.
• Decomposers recycle substances that would
otherwise remain useless.
Food Production
• Yogurt, sour cream and cottage cheese are
produced by bacteria.
• Bacteria also helps improve the flavor of
cocoa, tea and coffee. Even pickles and
sauerkraut are prepared with the help of
bacteria.
How are microorganisms harmful?
• Some microorganisms are parasitic, meaning
they cause damage to plants and animals.
• Some microorganisms make you feel sick,
while others can be deadly.
Harmful Microorganisms
• Infectious Disease: Some cause disease by
destroying cells directly. (Strep Throat, or
pneumonia)
• Bacteria cause disease by producing
poisonous substance toxins (poison).
• Bacteria also live in uncooked meats, raw
eggs, and other foods. E. coli and Salmonella
are two of the most well-known. Fever and
sore throat are two examples of symptoms.
Harmful Fungi
• Microorganisms can also harm plant life.
These are considered parasites because they
live on a host organism causing harm to it.
• In the nineteenth century, a fungus spread
throughout Ireland and destroyed large
amounts of the potato crop, causing
thousands to starve. It was known as the Irish
Potato Famine.
Harmful Fungi
• Athlete’s foot is another example of a disease
caused by harmful microscopic fungus. It is
found in damp places and lives on skin. The
symptoms include itching and blisters
between a person’s toes.
Protists
• Parasitic protists can also cause health
problems in animal species.
• Malaria is an example of a parasitic protist.
The protist is spread by the mosquito and
then reproduces inside red blood cells,
destroying the blood cell. When the blood
cells are destroyed new parasites are released
into the animal.
• Results, severely high fever and the chills.
How do we protect ourselves?
• Antibiotics are used to treat bacterial
infections. Antibiotics stop the growth of
bacteria. Antibiotics are produced from
bacteria and molds, and are artificially
produced in labs.
• Each antibiotic only works on certain types of
bacteria.
• For each new bacterial infection, new
antibiotics must be developed!
Food Safety
• Pasteurization is used to ensure the safety of
our food. Heating milk and other liquids to a
high temperature kills the bacteria without
altering the liquid.
• Cooking also destroys harmful bacteria in
food, by destroying the bacteria cells.
• The government also has food inspectors to
ensure the safety of foods.