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Gram Negative Bacilli Identification
WebQuest

By Kathleen P. Lauber

Kathleen Lauber, Associate Professor
College of Southern Maryland
 

Updated Summer 2008

 

Introduction  |  Task  |  Process |  Resources |  Evaluation  |  Conclusion

 

Introduction:

 

You are the newest member of the “MIT” crew (Microbe Identification Team) of the Charles County CSI lab. Identification of Gram-negative bacilli can seem quite over whelming due to the quantity of biochemical testing available. Completion of this exercise will familiarize you with the basic biochemical tests used to identify Gram-negative bacilli.

 

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The Task:

 

This virtual reality laboratory exercise will involve the following:

 

1.     Researching thirteen biochemical tests used to identify Gram-negative bacilli

2.     Compiling a chart about the biochemical tests

3.     Complete biochemical test questions

4.     Selecting a bacterium to identify (Down to genus and species)

5.     Researching the identified bacterium as to: its natural habitat, optimum growth conditions, pathogenic capabilities, disease symptoms and treatments as well as antibiotics to which the bacterium is resistant

6.     Compiling a final report on the identified bacterium

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The Process:

Research:

1.     Each student will research the following Biochemical tests

1.     Identify what a positive and a negative result looks like

2.     Explain the purpose of each test (what is being tested for)

3.      Complete the chart provided (See Data Sheet)
- Phenol Red Carbohydrate Broth
- Urease production
- H2S production in SIM media
- Motility
-Indole production
-Methyl Red test
-Voges Proskauer test
-Citrate utilization
-Decarboxylase production
 

4.      Answer biochemical tests questions

 

Identify a Bacterial Unknown:

 

  1. Select an unknown bacterium (should correspond to your laboratory seat number)
  2. View the test results of the biochemical tests
  3. Record your results on the chart provided
  4. Use bacterial identification chart to identify your unknown by genus and species

Compiling Final Report - All parts of this report are to be typed

    Final project report to include:

1.      Data chart of biochemical tests and your results (in-body referencing required)

2.     Written portion:

a. Description of Natural Habitat of the bacterium and optimal conditions for growth (oxygen, temperature & pH)

b.      Pathogenic capabilities of the bacterium

Pathogenicity is the ability of a bacterium to produce a disease when it enters a host and is dependent upon: the ability to invade the host, the ability to replicate once it has entered the host, and the ability to avoid damage from the hosts’ immune system.

Virulence factors aid the bacterium in its ability to cause disease. They may include: pili for attachment, enzymes such as streptokinase, hyaluronidase or coagulase, endotoxins found within bacteria cell walls & released when replicating or at death causing rapid decrease in blood pressure, or capsules used to evade phagocytosis.

The student needs to research this topic and find out what virulence factors the bacterium uses when it causes disease in   man.     

c.       Symptoms produced when this bacterium invades man

 

d. Treatment – in order to prescribe an antibiotic sensitivity testing needs to be done on each bacterium. Recently there has been a tremendous increase of bacterial resistance. Which antibiotics are no longer useful for treating your bacterium and which can be used to treat this bacterium?

 

e. In body referencing required within this section

3.  Biochemical test questions (in-body referencing required)

 4. Evaluation of activity (see conclusion)

 5. Work cited page

 

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Resources: These are suggested Internet sources only. There may be better sites out there or the Hard copy sources listed below may be useful. You do not have to use internet sources to do this activity.

 

    Internet sources:

·        Textbook of Bacteriology - (hyperlink to http://textbookofbacteriology.net)

·        Microbugz – (hyperlink to www.austin.cc.tx.us/microbugz)

·        Microbiology Tests for Identification of Gram Negative/Enteric Bacilli –
www.studystack.com/java-studysta/menu-9401

·         Merck Manual – (hyperlink to www.merck.com/mrkshared/mmanual/home.jsp)

·         Biochemical tests - http://web.fccj.edu/~lnorman/unknowns.htm?index=2

·         Biochemical tests - www.campbell.edu/faculty/thyou/Bio334L/MetabolicTest.pdf

 

   Hard Copy Sources:          

 

          Bergey’s Manual of Determinitive Bacteriology, Holt  (ed.) – available in library & lab

          Student Laboratory Atlas: A Photographic Atlas for Microbiology Laboratory by LeBoffe & Pierce

          Manual of Clinical Microbiology, Murray et.al. – Available in the library

 

          Data Chart

          Biochemical Test Questions

          Unknown Selection

          Bacterial Identification Chart

          Reference page assistance – (hyperlink to www.noodletools.com)

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Conclusion(Evaluation):

 

Now you have learned what is involved with the identification of Gram-negative bacilli. And you should have an opinion on the use of virtual reality laboratory exercises in Biology 2010 based on the research required to complete your Biochemical unknown. Answer the following questions and submit your answers along with your final report.

(Students must explain their rating to receive full credit)

 

1.      How would you rate the virtual reality laboratory exercise as to its interest level?
(Consider 1 as the lowest rating and 5 as the highest rating)

 

2. How would you rate the virtual reality laboratory exercise as to its challenge?
(Consider 1 as the lowest rating and 5 as the highest rating)

 

3. How could the exercise be made a better learning experience?

 

 

Grading Rubric - Total Points for Project: 100 points

 

                   Grade Evaluated on:

 

                1. Data Chart  - 20 points

                2. Biochemical test questions – 20 points

                3. Identification of Unknown – 10 points (10 if id on first try, 5 if 2 or more tries)

                4. Written Portion – 20 points (each item worth 4 points) See final report for details

                        a. Natural Habitat

                        b. Optimal Growth Requirements                       

                              c. Pathogenicity                                                             

                        d. Symptoms of Disease

                        e. Antibiotic Treatment

                5. Conclusion Evaluation – 6 points

                6. In body Referencing – 12 points

                7.Work Cited Page – 12 points

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Kathleen P. Lauber

Kathleen Lauber, Associate Professor
College of Southern Maryland