Summer Research Program for Science Teachers

Melissa Webster

Hastings-on-Hudson High School, Westchester

2002

Antibiotic Resistance in E. coli

Introduction: Antibiotic resistance in bacteria is a serious problem facing society today. There are many reasons for this problem, one of which is an overuse of antibiotics. Through evolution, tougher bacteria that cannot be killed by antibiotics are surviving and reproducing. This is not necessarily a problem in people with strong immune systems, but in hospitals where many people have compromised immune systems, harboring such bacteria can kill a person. In this laboratory investigation, you will be designing an experiment to test the concept of antibiotic resistance using two strains of bacteria called E. coli.

Materials:

The following items will be available for your use in this laboratory investigation:

· Agar plates for growing bacteria:

üRegular agar plate

üAgar plate with the antibiotic ampicillin

· Two strains of E. coli

üE. coli

üpAMP: a type of E. coli that has been transformed to include a gene for antibiotic resistance

· Sterile plastic inoculating loops

Procedure:

Each group of students will be responsible for creating an experiment with the above materials to test the bacteria for antibiotic resistance. You must use all of the materials given above. If there is something else that you would like to use, please ask and I will see if I can obtain it. Think closely about what the bacteria and agar have or do not have to help you design your experiment.

EACH STUDENT will be responsible for handing in her/his own lab report. Therefore, each of you will need to be writing your own information.

Day 1: Design your experiment. Remember to use your “Scoring Guide for Writing a Lab Report” rubric to help you design the experiment and ensure that you have all the components. Remember to consider the following:

üWhat is the problem?

üHypothesis?

üWhat will you use as a control group?

üWhat are the independent and dependent variables?

üWhat will your procedure be?

üHow will you collect and analyze your data?

Day 2: Perform your experiment! Make sure that you have all the necessary supplies prior to starting. Appendix 1 reviews the method for streaking yeast cultures onto an agar plate.

Day 3: Analyze your results.

üCollect your data.

üDid you prove or disprove your hypothesis?

üWhat do your results tell you about antibiotic resistance?

üWhat could be some of the sources of error in your experiment?

üWhat could you have done to make this a better experiment?

Notes to teachers:

1.   Carolina Biological sells the AP biology transformation lab, which uses ampicillin resistant plasmids. However, in an AP class, students perform the transformation, and then plate the bacteria. In a Regent’s class you could still do the transformation with them depending on your students, materials and time, or you could prepare it yourself. I plan to offer my students the chance to do the transformation with me outside of class time.

2.   Remember that you need to destroy the transformed bacteria prior to throwing it away. You can soak it in a bleach solution for 30 minutes prior to disposing.

Standards Addressed:

ØScience Teaching Standards: A, B, and E

ØAssessment Standards: A and D

ØContent Standard: C (Life Science), E (Science and Technology) and F (Science in Personal and Social Perspectives)

ØScience Education Program Standards: B

Appendix 1: How to Streak Bacteria Cultures

1.   Obtain a sterile plastic inoculating loop, bacterial culture, and agar plate.

2.   Write the name of the medium and the type of bacteria on the bottom of the agar dish (the side with the agar).

3.   Of great importance is maintaining a sterile environment so that you do not contaminate your culture or plate.

Some important notes:

üKeep your plate closed at all times unless you are streaking your culture. When it is open, you are exposing it to bacteria that are in the air and can cause contamination.

üTry not to hold the plate too close to your head when you are streaking because breathing on the plate can also increase the chance for contamination.

üMake sure that you use new inoculation loops for each culture; otherwise, you will contaminate the cultures of bacteria.

5.   Immerse your inoculating loop into the tube with the bacterial culture. The loop should be filled with fluid.

6.   Streak your plate using the following picture as a guide:

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