Biology Commonwealth of Virginia

Name: Date:

Background

Procedure

1. From the list found under “School Location” in the Class Data Table, choose five locations at school that may have large numbers of bacteria.

2. Rank the locations where the most bacteria may be found, #1 being the location most likely to have the highest number of bacteria. Explain your reasoning.

3. From the original question, formulate a hypothesis, using the words if and then to describe how the sampling will test the question. Record your hypothesis on the Class Data Table.

4. On the Class Data Table, describe the reasoning for finding high numbers of bacteria. Use words such as damp, warm, sweaty, nutrients (food) available, not cleaned/sanitized frequently, and special.
At the sampling locations:

5. Take a test tube half-filled with deionized sterile water, a stopper, and a cotton swab to one of the locations selected.

6. Dip the cotton swab into the water in the test tube.

7. Roll the wet cotton swab over the sampling location surface.

8. Put the cotton swab into the test tube.

9. Put the stopper in the test tube, and label the tube with the location.

10. Repeat steps 5–9 for the four remaining locations.

10. Return to the classroom.

11. Record initials, date, and locations of samplings on Petrifilm™ plates.

12. Shake a stoppered test tube containing one sample 25 times.

13. Remove the stopper from the tube.

14. With pipette, withdraw 1 mL of the water from test tube.

15. With Petrifilm™ plate on flat surface, carefully peel open top film layer, being careful not to touch either the film layer or yellow-hatched gel layer.

16. With pipette perpendicular to Petrifilm™ plate, dispense the 1 mL sample onto the middle of the yellow-hatched layer. Drop top film layer onto yellow-hatched layer. Do not roll top film layer down onto yellow-hatched layer.

17. Press with spreader, ridge side down. Do not twist.

18. Lift spreader. Wait one minute as gel solidifies.

19. Repeat steps 12–18 for each of the other samples.

20. Place each plate in a separate bag. Do not seal: this is an aerobic count.

21. Carefully dispose of all plate-preparation materials according to teacher directions.

22. Incubate plates with clear side up for 48 ± 2 hours at 35ºC.

23. Count plates according to the instructions available from the 3M™ Worldwide Web site at http://multimedia.mmm.com/mws/mediawebserver.dyn?ddddddNLXpsdyHedrHedddavSP&j7L9d- (If this does not work, go to http://www.3m.com/ and search “Petrifilm Aerobic Count Plate Interpretation Guide” to find the link to the PDF brochure.)

Discussion and Conclusions

After the plates have been counted, record data in Class Data Table.

1. Which plate had the most bacterial colonies?

2. Which plate had the least?

3. How did the actual class results compare with the predicted results?

4. Why was a control necessary?

5. Explain any unexpected results.

6. From the results, where are the highest number of microorganisms (bacterial load) found in the school?

7. What is the effect of hot water/soap/detergent/sanitizer on the number of microorganisms? (See results from the clinic/cafeteria/restrooms.)

8. Discuss why sanitation has become so important in the world today.
Prokaryotes in the School Environment

Class Data Table

School Location	Predicted Ranking	Reasoning	Number of Aerobic Bacteria			Actual Ranking
Women’s restroom
Sink
Door handle
Flush handle
Wastebasket
Men’s restroom
Sink
Door handle
Flush handle
Wastebasket
Main door handle
Office door
Clinic door
Clinic desk
Clinic telephone
Women’s locker room shower
Men’s locker room shower
Cafeteria
Tables
Garbage cans
Public phone receiver
Water fountain handle
Computer lab keyboard
CONTROL

Hypothesis:

Do you accept your hypothesis? ___________ Why?

Viruses

Organizing Topic Investigating Cells

Overview Students learn about the life cycle of organisms that cause some of the deadliest diseases known.

Related Standards of Learning BIO.5a, b, c

Objectives

The students will

• 
  distinguish between viruses and cells;
  
• 
  illustrate the viral reproductive cycle.
  

Materials needed

• 
  Reference books
  
• 
  Markers, rulers, chart paper
  
• 
  Access to Internet
  
• 
  Presentation software, poster board, transparencies
  
• 
  Attached directions for skits
  

Instructional activity

Content/Teacher Notes

Viruses are not considered living organisms outside their host cells. They are obligate intercellular parasites that require a host cell to reproduce. Most viruses are genetic information (DNA or RNA) surrounded by a protein coat. They do not fit into our six-kingdom system, but they do have a classification structure all their own. Some DNA viruses that may be familiar are Adenoviruses (respiratory infections, such as colds), Herpesviruses (herpes), Papillomaviruses (HPV), Polyomaviruses, Parvoviruses (feline or canine parvovirus, “slapped cheek” virus), and Poxviruses (chickenpox, smallpox). RNA viruses include H5NI (avian flu), coronaviruses (SARS), and retroviruses (HIV).

Why have we not known about viruses until relatively recently? Consider the scale below and the fact that the scanning electron microscope was not in use until after 1965.

http://www.biology.arizona.edu/cell_bio/tutorials/cells/cells2.html

In order to understand the reproductive cycles of viruses, students need to understand the definitions of the following terms as they apply to virus particles: capsid, nucleic acid core, adhesion, penetration, replication, assembly, lysis, viral membrane coat, lytic cycle, lysogenic cycle, virulent, and latent.

For advanced discussion, you may wish to add Human Endogenous Retroviruses (HERV), which are found in 85 percent of Gulf War veterans.

Introduction

At this level, not much can be done with laboratory investigations of viruses. Nevertheless, students can develop an understanding of the terms and concepts if their task is to “teach” the topic and to prepare a presentation to be used for that purpose. Individuals or teams of students can address the terms and concepts of viruses by explaining to other students what the terms are, how they relate to each other, and how they impact health-related topics.

Procedure

1. Have students or student teams use the materials listed above (or some of their own choosing) and/or presentation software to prepare a product that demonstrates an understanding of the viral lytic and lysogenic cycles.

2. Have students or teams present their products to other students, thereby demonstrating and reinforcing their understanding.

2. In the products and presentations, make sure students demonstrate an understanding of the importance of knowing how the various phases occur and how viruses are of great concern in health-related fields.

Observations and Conclusions

1. Have students demonstrate an understanding of the lytic cycle from adhesion to lysis and describe differences between it and a lysogenic cycle.

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