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1. Science of Microbes
Activity 5
The Variety and
Roles of Microbes
PowerPoint Slides and
Notes by Alana Newell, BS
Activity by
Nancy Moreno, PhD,
Barbara Tharp, MS, Deanne
Erdmann, MS, Sonia
Rahmati Clayton, PhD, and
James Denk, MA
BioEd Online

2. BioEd Online
Materials for Each Group of Four Students

3. BioEd Online
Safety Considerations
Follow all instructions.
Begin investigation only when
instructed.
Have a clear understanding of the
investigation before starting.
Wash hands thoroughly after the
investigation.
BioEd Online

4. BioEd Online
What Do You Know About Microbes?
Can you name some different types
of microorganisms?
What roles might microorganisms
play in nature?
What roles might microorganisms
play in humans?
What roles might microorganisms
play in industry?
Paramecium sp.

5. BioEd Online
How Might You Organize Your Microbe
Example Cards?
What are the similarities and
differences between the items on
your microbe example cards?
How might you organize the microbe
example cards into groups with
similar roles?

6. BioEd Online
Let’s Reorganize
Rearrange your cards into the following
three groups.
Role in Food Production
Role in Causing Disease
Role in the Ecosystem/Environment
Are you surprised by the roles of
microorganisms in any of these three
groups?
Influenza virus
particles

7. BioEd Online
A Closer Look at Microbes’ Roles
Role in Food Production
Microbes are used to prepare many
foods, including bread, yogurt and
cheese.
Role in Disease
Pathogenic microbes invade a host
and harm the host’s cells.
Role in the Environment
Microbes have important roles in all
ecosystems, and play a key part in the
decay of organic materials.
Malaria parasite
(Plasmodium sp.)
inside a red blood cell.
Lactobacillus sp. is
used for production
of yogurt and many
other foods.

8. BioEd Online
Comparing Groups of Microbes
Viruses Bacteria ProtistsFungi
Single-celled? None All Some Some
Multicellular? None None Some Some
Cell membrane? None All All All
Organelles? None None All All
Well-defined nucleus?None None All All
Cell wall? None Some Some Some
Autotroph? None Some Some None
Heterotroph? None Some Some All
Microscopic? All All Some Some
Motile? None Some Some None

9. BioEd Online
Organizing by Microbe Groups
Read the four Microbe Group cards
and discuss the information on each
card.
Place the Microbe Example cards
related to food production by the
appropriate Microbe Group.
Consider, “Which Microbe Groups
are involved with food production?
Are you surprised?”

10. BioEd Online
Examples of Microbes in Food
Production/Processing
Beer
Fungi(specifically a species of baker’s yeast) is used to
ferment barley, wheat, hops and sugar to create beer.
(Fermentation is a process by which yeast produces CO
2and
ethyl alcohol as it breaks down food in the absence of oxygen.)
Pepperoni
Bacteriaferment a dried meat mixture, creating lactic acid,
which contributes to the flavor.
Chocolate
Bacteria and Fungi (in this case, yeast) are used to ferment
cacao seeds, enabling the complex flavors of chocolate to
develop.

11. BioEd Online
Organizing By Microbe Groups
Place the Microbe Example cards related to disease by
the appropriate Microbe Group.
Consider, “Which Microbe Group(s) contribute to
disease?”
Pathogens are microbes that cause disease in animals,
plants and/or humans.
Can one group of microbes cause disease in another
group of microbes? Can you think of any examples
when this happens?

12. BioEd Online
Diseases Caused by Microbes
Mosaic Disease
A virus(tobacco mosaic virus) can infect several kinds of
related plants and can cause severe crop losses.
Stomach Ulcer
A specific kind of bacteriadamage the protective lining of a
host’s stomach and part of the small intestine, causing pain
and other uncomfortable symptoms.
Malaria
A parasitic protistcauses this potentially fatal disease. Host
organisms are infected when bitten by a parasite-carrying
mosquito. Protists then destroy red blood cells, sometimes
resulting in death for the host.

13. BioEd Online
Organizing by Microbe Groups
Place the Microbe Example cards related to
ecosystem/environment by the appropriate Microbe
Group.
Consider, “Which Microbe Groups contribute to the
ecosystem/environment? Why can’t we see microbes
working in the ecosystem?” and “What general
statement can we make about the importance of all
microbes?”

14. BioEd Online
Examples of Microbes in the Environment
Nitrogen
Through a process called nitrogen fixation, bacteriain the soil
transform the essential element, nitrogen, from a difficult-to-
use, naturally occurring form (N
2) into more easily usable
compounds.
Green Pond Water
Bacteria and Protists with a blue-green color, such as algae
and cynobacteria, can cause fresh water to appear green.
They form the bottom of the food chain in aquatic
environments.
Compost
Bacteria and Fungihelp to break down organic material in soil
and release important forms of nutrients for absorption by
plants.

15. BioEd Online
Extensions
What are other examples of
foods produced by using
microbes?
Investigate the processes
by which common foods
like root beer, cheese, soy
sauce and vinegar are
made.