GERMS: HEROES AND VILLAINS
Demonstrations for children with adaptation
for teens and adults
Teach children that germs are everywhere in our environment, and that they can be good or bad. During
this activity, participants will have the opportunity to manipulate models of germs that cause our food to
rot. Play the match-up game to discover some germs frequently used by humans to their advantage as well
as some of the dangers they may pose to our health.
Learning results
Participants should be able to:
recognize that our food rots because germs feed on it
name a few germs
describe some ways to use germs to fulfill our needs
Materials
Materials
-
-
Four giant germs
o Clostridium botulinum - bacterium (orange)
o Acidophilus - bacterium (purple)
o Yeast - fungus (white)
o Penicillium - fungus (blue)
12 picture cards for the match-up game (3 per germ)
Four germ profile cards (1 per germ)
Small demonstration table
Instructions
Preliminary questioning
1. Where,
Where , then?
then ?
Explain that germs, or microorganisms, are tiny living entities that can only be seen with a
microscope. They may become visible when they form a colony, which is a large group of
individuals. Ask participants where germs could be found. They are everywhere: in the
ground, in the air, in our food, on and inside our body, on objects we touch with our hands
(telephones, door-knobs, counters, etc.).
GERMS: HEROES AND VILLAINS – PAGE 2
2. Good or Bad?
Bad ?
Ask participants whether germs are good or bad, and why so. Explain that germs make our
food rot and may make us sick when they invade our body or when we ingest their waste,
which can be toxic. This is why we have to wash our hands and why it is necessary to
destroy germs, that is to disinfect, the areas where food is prepared. However, germs may
be good. Humans use some germs in a useful way.
3. What kingdom
kingd om do germs belong to?
to?
Ask participants whether, in their opinion, germs that cause our food to rot are animals,
plants, or something else. After listening to the answers, state that germs are generally
bacteria or fungi (plural of “fungus”, i.e. mushroom) and therefore are neither animals nor
plants, not even insects, which belong to the animal kingdom.
Bacteria are among the simplest life forms. They comprise a single cell (i.e. a shell)
and do not have the complex cellular structures (nucleus and other organelles) that
are found in animals, plants and fungi.
Fungi are not plants: they do not produce their energy through photosynthesis like
plants; they get it from decomposing organic matter.
Notes for educators:
•
A fungus is neither a plant nor an animal; fungi are classified within their own
kingdom: the kingdom Fungi. The kingdom “Plantae” comprises all photosynthetic life
forms. Single-celled photosynthetic algae are not considered plants but they still
belong to the kingdom “Plantae”.
•
Microscopic life forms (germs) are found in all kingdoms. This activity focuses on
microorganisms that belong to the kingdoms Fungi and Bacteria, to make it simple.
4. Advise participants that they are going to examine four different types of germs which are
often guilty of spoiling our food but, sometimes, are very useful. Present the germ models
one by one and let participants manipulate them.
Manipulation
1. Introduce the image cards. Explain that these images represent some positive and negative
aspects of four common germs.
2. Use the germs’ profile cards to describe each one. Participants read the information on the
cards if they are able to. After the participants have read the germ profile card, ask them
to find the corresponding images. Place the image cards and the corresponding germ cards
on the table. Provide guidance to help participants find the links between what they have
read or heard and each image.
GERMS: HEROES AND VILLAINS – PAGE 3
3. After all images are associated with the germs, review the answers and make corrections if
required. Summarize through asking participants again whether germs are good or bad.
They are good when they are useful to humans (ex.: transform or preserve food, produce a
medicine, control diseases, etc.); they are bad if they invade human food and degrade it to
feed themselves. Some germs are rather good, some rather nasty. What is the most
dangerous one for human beings? Clostridium botulinum.
Adaptation for older participants:
participants:
-
Do the match-up game as a quiz. Show participants the four germs and the image cards.
Ask them to figure out which three cards have to be associated with each germ without
reading the related information. Their answers should be based on previous knowledge. The
germs’ profile cards can be read afterwards.
Adaptation for very young children:
children:
-
Stick to very basic concepts: yeasts make bubbles in bread, penicillium brings mould,
Clostridium botulinum causes a lethal disease called botulism, and acidophilus transforms
milk into yogurt.
GERMS : HEROES AND VILLAINS
V ILLAINS – ANSWERS
Penicillium chrysogenum (fungus
(fungus)
fungus)
My name is Penicillium chrysogenum, but they also call me “penicillium” or “blue mould”. I am a fungus, or a mushroom
if you like. In labs, scientists use me to make an antibiotic called penicillin. That’s a medicine which kills bacteria that
make you sick.
I love cold and damp places like the inside of your refrigerator. I feed on your food and coat it with a white or bluegreen layer called mould.
mould You will frequently find me on bread and citrus fruits.
People love the taste and the colour that some types of penicillium give to blue cheese like Stilton or Roquefort or
the crust that is seen on camembert and sausages. Caution: some types of penicillium are not edible! Some of us
produce toxic waste that could make you sick.
mould
blue cheese
antibiotics
Saccharomyces cerevisiae (fungus
(fungus)
fungus)
My name is Saccharomyces cerevisiae, but most people know me by the name of “brewer’s yeast”. I am a fungus
made up of only one cell. Without me, you would not have yeast-raised bread and grapes would never become wine.
I love comfort. I live and breed in very damp areas, moderately warm and low in acid. My preferred food is sugar
(carbohydrates) from various sources: fruits such as grapes, grains such as wheat, honey, etc.
People like me because when I digest my meals in an oxygen-free environment, I release carbon dioxide (a gas) and
alcohol.
alcohol This is useful for human food transformation and preservation. Alcohol prevents bad microorganisms from
getting into food. But watch out: I may also spoil your food!
fruit fermentation
grain fermentation
bread bubbles
GERMS : HEROES AND VILLAINS – ANSWERS
Clostridium botulinium (bacterium
(bact erium)
erium)
My name is Clostridium botulinum. I am a bacterium that is very hard to kill because I can hide as a spore when I am
in the proper environment.
I am found in the ground and I can contaminate harvests. I like nutrient-rich food but I hate acid, salt and oxygen. I
can be found in poorly sterilized food cans, where conditions are perfect for me to feed and breed.
Caution! I produce an extremely dangerous waste called a toxin which, even in minute quantities, causes botulism.
This paralyzing disease can cause death.
death Although highly toxic, this toxin can be used to solve various health
problems associated with muscles. Cosmetic surgeons can even inject it in small, controlled doses in their patients’
facial muscles to temporarily which reduce the appearance of wrinkles.
paralyzing disease
cosmetic injections
death
Lactobacillus acidophilus (bacterium)
(bacterium)
My name is Lactobacillus acidophilus but I am generally called “Acidophilus”. I am a bacterium and I am good for your
health as I am a probiotic.
I love damp and warm environments with a low to medium acid level. Since acid does not harm me, I survive the
journey through your digestive track down to your intestine. There, I help you digest your food and I protect you
against bad bacteria and bad fungi.
I feed on carbohydrates (sugar) such as found in milk, fruits and vegetables. When I digest my food, I release lactic
acid that transforms milk into yogurt and preserve vegetables in brine. I also release peroxide and bacteriocins.
These products prevent the growth of other bacteria.
transformation of milk into yogurt
bowel health
fruit and vegetable fermentation