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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 AMBIENT Rev 2 7/8/2004 42 Water Module Viewing Bacteria 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 AMBIENT Rev 2 7/8/2004 43 Water Module Viewing Bacteria 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 AMBIENT Rev 2 7/8/2004 44 Water Module Viewing Bacteria 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 AMBIENT Rev 2 7/8/2004 Slide 8 45 Water Module Viewing Bacteria 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 AMBIENT Rev 2 7/8/2004 46 Water Module