Introduction:
 

Safe laboratory use and disposal of bacterial cultures. Basic knowledge od use of agar plates. A little about how diseases spread: epidemiology.
 

Group Size: Any
 

Learning Objectives:
 

Scientific Method, deductive reasoning, epidemiology, bacterial diseases.

Students will learn how epidemiologists determine the vectors of diseases. The lab uses a CSI style methodology to engage student interest.

They will also learn:

  • basic bateriologic techniques
  • methods of safe handling and disposal.

 

Guiding Question:
 

Which class member contaminated the class? How is this a reasonable model of the spread of infectious diseases, such as chicken pox, influenza, or HIV?
 

Materials:
 

Materials per person:

  • one glove (diposable food handlers gloves work well and are fairly inexpensive)
  • one nutrient agar petri plate
  • one numbered cup containing wet candy
  • data table to record all interactions and results
  • two cotton swabs
  • two small pieces of tape to seal petri plate
  • contaminated waste disposal bag for entire class
  • Teacher supply only: Autoclave to sterilize wastes or a large tub or trashcan with bleach solution for overnight soaking.

 

Procedures:
 

I) Obtain materials: CAUTION: the lid on petri plate must be on unless the dish is in quick, immediate use, otherwise contamination will result!

2) Each person puts a plastic glove on the hand they DO NOT WRITE WITH

3) A numbered cup of wet or contaminated candy is obtained. Record the cup number, then put the candy in the gloved hand and "work' the candy around until the glove is sticky. Be careful not to touch any other surfaces with the glove or the candy.

4) Shake hands with one other person (quickly each of the shakers records the name of who the shake with).

5) Shake hands with a second person, again recording the NUMBER

6) BEFORE shaking again - take one of the swabs and roll it over you glove. Then lightly swab the half the surface of the nutrient agar plate with the number one on it.

7) Discard the swab in the contaminated waste.

8) Repeat steps 4-7, only use side 2 of the petri plate.

9) Be sure both people who shake hands record the shake THIS IS VERRRRY IMPORTANT!!!!!

10) label the clear lid of the plate with your name and period number, keep the writing small and near the edge, otherwise it will obscure your vision.

II) Use the three pieces of tape to hinge the plate shut, never remove these tapes.

12) Clean table with alcohol. Incubate plate upside down in the cupboard designated, check each day for results. You will see pink bacterial colonies if your result is positive for contamination.

13) Record results on class data table, copy all data, now solve the problem.


 

Assessment:
 

Students write a summary of the process and the reasoning they used to determine who had the original "disease". Teacher can stamp or initial the work and then as a class decide the real source of the disease. Then all students go back to add to their reasoning/conclusion any new ideas learned through the class discussion. Generally full participation gets a high score. It is more important that the students thought about the process, than the correct result.
 

Answer Key or Rubric:
 

Here is a sample data sheet from one of my classes:

CUP# /NAME

Round 1

Rnd 2

+/-

Rnd 3

Rnd 4

+/-

  1. SHETA
18(DUSTIN)

9
 

5

13
 

  1. DAVID
JOSH

15

22
 

7

9
 

21

11
 

31

4
 

  1. RYAN
7

8
 

14

23
 

  1. KYLE P-R
21

8
 

6

15
 

  1. LAUREN
24

34
 

25

1
 

  1. LAUREN L.
33

25
 

34

4
 

  1. ERIC C
21

12
 

3

14
 

  1. ERIC MC
26

4
 

22

3
 

  1. KYLE
18(DUSTIN)

1
 

20

19
 

  1. NICK
16

28
 

22

21
 

  1. RORY
31

18(Paula)
 

29

2(JOSH)
 

  1. MAURICIO
7

23
 

3

29
 

  1. AMANDA
17

18(DUSTIN)
 

1

19
 

  1. LAURA
20

23
 

3

7
 

  1. DANIELLE
29

12
 

28

4
 

  1. DEREK
24

20
 

10

28
 

  1. ADAM
33

13
 

19

18
 

  1. DUSTIN
1

9
 

19

13
 

  1. AMY
18(DUSTIN)

17
 

9

13
 

  1. HENRY
16

14
 

18(DUSTIN)

9
 

  1. SEAN
4

7
 

10

2(JOSH)
 

  1. MATT
26

27
 

8

10
 

  1. ALYSSA
14

12
 

27

3
 

  1. VANNDON
16

5
 

26

27
 

  1. AMELIA
6

34
 

33

5
 

  1. ARI
8

24
 

22

27
 

  1. JULIAN
24

22
 

26

23
 

  1. SPENCER
16

10
 

18

15
 

  1. ELLEN
15

12
 

11

28
 

  1. -
-

-
 

-

-
 

  1. VINNIE
11

18
 

2(josh)

-
 

  1. -
-

-
 

-

-
 

  1. SHELBY
6

17
 

25

34
 

  1. CATHERINE
5

25
 

33

6
 

?? PAULA 11,28,17,31


 

Benchmark or Standards:
 

California Science Standards- Biology:

Cell Biology

    1. Students know how prokaryotic cells, eukaryotic cells (including those from plants and animals), and viruses differ in complexity and general structure
Physiology

Students know the role of the skin in providing nonspecific defenses against infection.
 

d. Students know there are important differences between bacteria and viruses with respect to their requirements for growth and replication, the body's primary defenses against bacterial and viral infections, and effective treatments of these infections.

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