Download Viewing Bacteria

Viewing Bacteria
Viewing Bacteria
Purpose
To compare E.coli with other bacterial cells and observe the structures within the bacterial cells.
Overview
This investigation is to familiarize students with the characteristics of E.coli and other harmful
bacteria. Students will use microscopes to observe E.coli bacteria on prepared slides and in a
live culture. Students will use micro-slide viewers to observe the shapes of various bacteria and
the structures within the bacterial cell.
Time
1 class period
Key Concepts
Bacterial cells are quite simple and different from animal cells.
Bacterial cell shape or structures (such as cilia and flagella) can be important factors relating to
their survival within their natural environment.
Skills
Making observations
Forming hypotheses
Comparing similarities and differences among organisms
Understanding and describing interrelationships in nature
Communicating observations and interpretations graphically and in writing
Materials
Class set of microscopes
Prepared slides of E.coli bacteria
Live Culture of E.coli bacteria
Microscope cover slips
Class set of micro-slide viewers
Micro-slide lesson set – Harmful and Helpful Bacteria
Facilitator Preparation
The micro-slide viewer is used to view 35mm photomicrographs. The Harmful and Helpful
Bacteria Lesson Set consists of images as photographed through a microscope, plus
accompanying text folders. Arrows and letters printed on the micro-slide help the student locate
important features to be studied. Each student views the same carefully selected images. The
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film is mounted in a clear acetate holder which protects it on both sides. Micro-slides cannot be
scratched.
Background
Discuss with students the various environments in which bacteria can be found. What are some
adaptations that various bacteria have to help them survive in so many different environments?
Ask students if they think that one type of bacteria has a wide tolerance range for different
variables or do they think that there are many different species of bacteria.
Procedure
PART A - Microscopes / E.coli Prepared Slides and Live Culture
Students will begin the activity by observing E.coli bacteria under the microscope.
1.) Microscopes should be set up with two students at each station.
2.) Pass out the prepared slides of the E.coli, one per station.
3.) Go over the Worksheet with students. Instruct them to use the first circle (labeled Slide 1)
for the prepared slide of E.coli and to use the next circle (labeled Slide 2) for the live culture
of E.coli.
4.) Have students draw what they see as they look at the prepared slide through the
microscope.
5.) Next, have students draw what they observe while looking at the live culture of E.coli
through the microscope.
6.) Students discuss their observations and compare the differences between the prepared
slide and the live culture of E.coli.
PART B - Micro-viewers / Harmful and Helpful Bacteria
After viewing the E.coli bacteria under the microscope, make students aware of some of the
many different types of bacteria. Explain to the students that they are going to observe the
same image as if they were looking through a microscope, but by using the micro-slide viewers,
we can be sure that all students are observing the same image.
1.) Pass out the micro-slide viewers so that each student gets their own viewer.
2.) Tell students to draw exactly what they see as they look through the micro-slide viewer for
each of the numbered slides 3-8 on their worksheet. Some students may have trouble
beginning this task if they do not feel comfortable drawing. The circle is to symbolize the
exact view that they see as they look down the tube of the micro-slide viewer and see the
image of the bacterial cell.
3.) When finished, have students read the accompanying text and answer questions on the
exercise sheet.
Student Assessment
Give students points for the following tasks
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Using the microscope
Working with the live bacterial culture safely
Using the micros-slide viewer
Drawing in each circle
Labeling each drawing with the appropriate name
Writing in each question
Answering questions citing a specific resource with appropriate content
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Student Canvas and Worksheet
Directions: Draw what you see in each slide. Comment on your observations. Take note of
particular characteristics of the organisms (color, size, shape, etc).
Bacteria Name
E. coli
(prepared slide)
Bacteria Name
E. coli
(live culture)
Comments
Comments
Slide 1
Slide 2
Bacteria Name
Bacteria Name
Comments
Comments
Slide 3
Slide 4
Bacteria Name
Bacteria Name
Comments
Comments
Slide 5
Slide 6
Bacteria Name
Bacteria Name
Comments
Comments
Slide 7
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Exercise
Answer the following questions.
What are some bacteria causing disease in humans?
Are all bacteria harmful? What are some examples of helpful bacteria?
Write down 3 questions you have about the bacteria you have just viewed. Now use any type of
information resource to answer them, i.e. book, internet, interview teacher/scientist, experiment
Question 1
Question 2
Question 3
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