MICROBIOLOGY 101 LABORATORY MANUAL

EXERCISE #11-12: BACTERIAL UNKNOWNS

NAME, ID #:_______________________________________________

TA Name __________________________

REVISED: 08/04/99

INTRODUCTION

This exercise is designed to PULL TOGETHER everything that you have learned and practiced in the previous exercises. You will be given a culture that contains an UNKNOWN BACTERIUM. You will have to ISOLATE this bacterium and identify it using the procedures you have learned. In short you will be a MICROBIOLOGIST. This is the problem a LABORATORY TECHNICIAN in a hospital clinical lab faces when they receive an ill patient's blood, feces, sputum or throat swab. However, laboratory technicians are under considerably MORE PRESSURE than you will be, since you are only concerned about losing a few points if you get it wrong, whereas if the laboratory technician gets it wrong the patient may DIE or be SERIOUSLY HARMED. Do you think you could take that pressure and responsibility day after day for people's lives? It is also the problem a soil or plant microbiologist faces when they attempt to find out which microbe, among perhaps 10s of thousands, is effecting soil fertility, causing a plant disease or otherwise inducing some change of concern.

Your laboratory & observational skills will be challenged in this exercise. We all like to think that we are observant; i.e., that we would make a CREDIBLE WITNESS at a trial:

"The bank robber was a male, 6' 2", weighing approximately 165 pounds, with sandy brown hair, brown eyes and a tattoo on his right hand of a snake with the word DIE in red written across it."

Now if the robber actually turns out to be a 5' 4", 115 pound female with bright red hair and lacking a right arm, you could have a CREDIBILITY problem in the future. Nothing so permanent will result from a failure in this exercise I trust, as only your pride and a few points are at stake. Think of yourself as a microbial Sherlock Holmes and this as a mystery to be solved from the clues (DATA) you observe.

Review each of the appropriate previous exercises & Atlas sections before applying what you've learned to this exercise. You all lead busy lives and things can escape your memory. The instructor will outline a general approach, but you must sit down and carefully lay out the details of how to proceed. It is useful to talk over your plans with your lab partner or another friend in the class and exchange ideas on how to proceed. As your results come in consult with others in the class and with your instructor. However, the instructor will be trying to help you stand on your OWN COMPETENT feet, so they may not just "give" you the answer, but they may help you TO CRITICALLY THINK your way to a solution.

PURPOSE OF LABORATORY:

1. To test the skills you have learned in a practice "real life situation".
2. To reinforce what you have previously learned in the laboratory and lecture.
3. To test your competence in "problem solving".

RELATIONSHIP TO LECTURE MATERIAL

• NetText101/102: CHAP. VII

GENERAL INSTRUCTIONS:

1. Computers are available in SLIC. Prepare, as described below, a PRINTED REPORT on the COMPUTER of your procedures and conclusions and turn it in to the instructor for grading.

PROCEDURE:

1. Obtain your coded unknown from the instructor. RECORD its identification code on your Biochemical Characteristics table from the previous exercise #9-10.
2. Plan the steps you will follow in carrying out this exercise. Be sure and include a list of the materials you will need. The first step should be to do a streak plate: REMEMBER YOU WILL BE GRADED ON THIS.
   • Observe the colonies on the plate and include a description in your report.
   • Turn in the plate for grading.
3. Make sure that you include the proper controls.
4. Fill out your Biochemical Characteristics sheet and identify your unknown.
5. The Instructor will demonstrate the API and Enterotube system of bacterial identification.
6. You may use the report write up for you WRITING PORTFOLIO. 

GOOD LUCK AND HAPPY HUNTING!!!

INSTRUCTIONS FOR PREPARING MICRO 101 UNKNOWN REPORT

GENERAL

1. The report must be typed in the format described below in a font size of 12 or larger.
2. The report must be turned in at the second lab of the week of March 9 (before break).
3. The report will be graded both for the quality of its writing and its scientific accuracy. You are expected to use a Spell-Checker of the word-processing program you use. Good English and clear organization will be assessed.
4. You may want to keep this report in your WRITING PORTFOLIO.
   • You will have to get both your TA and Dr. Hurlbert (and the proper form from the Writing Center) to grade your report before using it in your Writing Portfolio.
5. Failure to turn this report in will result in an "F" in the course.

FORMAT

1. Cover sheet: Titled, UNKNOWN REPORT; To include your name, the course, section, due date and TA name.
2. Use the following headings: and include the appropriate information under each:
   • PURPOSE: To identify unknown bacterium (ID code of unknown).
   • INTRODUCTION: Explain how the staining, morphology and enzyme tests are employed to develop a profile or "fingerprint" of characteristics that can be used to identify unknown bacteria.
     • Although, these explanations are in the exercises and the Atlas, it is expected that you will put them into your own words. If you just copy the explanations you will be docked points.
   • METHOD AND MATERIALS: List each test you use (Gram stain, motility etc.) and briefly explain how each was performed. Include the medium used, the method of inoculation, the age of the culture (in hours) when tested, the temperature of incubation, any reagents used and their function (obtain this information from the Atlas).
   • RESULTS: Include the TABLE from exercise 9-10 to compare the results of each test performed or observation made on the unknown with those obtained with the knowns.
   • DISCUSSION: Describe the meaning of the results and observations. For example, if you have a positive urease test explain what has occurred to give that result; i.e., the cell produces the enzyme, _________, that breaks down the substrate, ________, to produce __________ & _____________. This causes the ________indicator in the medium to change from __________ to __________. Refer to your lab Exercises, the Atlas and your notes for this information. You are encouraged to discuss your data interpretation with your partner and others in the class.
   • CONCLUSION: State the putative identity of your unknown using its full scientific name (spelled correctly and written as a scientific name should be written; the instructor will ask you to pronounce the name of the bacteria correctly).
   • ATTACH TABLE: To the report.

Copyright © Dr. R. E. Hurlbert, 1999.
This material may be used for educational purposes only and may not be duplicated for commercial purposes.
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