BIOL260
Lab Practicum (Summer 2011)
Name____________________________
Please be concise with your answers. Areas where you are asked to “interpret the test” require you to
look at the test and tell if it is positive or negative. I will grade the first thing you write down so DO
NOT write more than is needed. (100pts total)
1. a. Place a check mark next to the thing(s) you observe on plate A:
Bacteria ____
Fungus ____
Virus
____
2pts
b. Place a check mark next to the thing(s) you observe on plate B:
Bacteria ____
Fungus ____
Virus
____
2. These three plates were exposed to UV for 30 seconds, 9 minutes, and 10 minutes.
a. Rank the plates in order of increasing UV exposure.
3pts
b. Which side of the plate (A or B) represents the control half?
c. What happens at the molecular level when bacteria are exposed to UV light? Be specific.
3. Which organism(s) is/are motile? Circle all answers that are correct.
a. Organism A
b. Organism B
c. Organism C
d. It is impossible to tell
2 pts
4. This blood agar plate contains a throat culture from a patient with a sore throat.
a. What type(s) of hemolysis is/are present on the plate?
3pts
b. Is this patient’s sore throat likely caused by a virus or by Streptococcus pyogenes? Explain.
5. What is the Gram reaction and morphology of the organism on the slide?
Would you expect this sample of bacteria to grow on an EMB plate? Explain your answer.
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3pts
6. This unknown organism was inoculated on mannitol salt agar. Examine the plate and
list two things that you know about this organism based on the growth on this plate.
2pts
A. ____________________________________________
B. ____________________________________________
7. Interpret the fermentation broths for all three organisms. Score the results as A(acid),
NA(no acid), G(gas), NG(no gas), or NGr (no growth).
Glucose broth
Lactose broth
Organism A:
4pts
Organism B:
Organism C:
Predict which organism(s) is/are NOT grouped with the coliforms: ________________________
8. This broth was streaked on this TSA plate to determine if the broth is a pure culture.
Is the broth a pure culture? Explain your answer.
2pts
9. An unknown organism was streaked onto this MacConkey agar plate and also onto this
2pts
TSA plate. Give a reasonable explanation as to why the organism did not grow on the MacConkey agar.
10. Examine the MacConkey plate and the lactose fermentation tube. Is it possible that
both contain the same organism? Explain your answer.
2pts
11. Which chemical disinfectant(s) (1,2,3, and/or 4) would you choose to inhibit
both organisms?
3pts
Which organism (A or B) seems the most sensitive to chemical disinfectants? Why might this be the
case?
12. Which organism (A, B, or C) can metabolize urea but not citrate?
13. This TSY plate is from the first session of the transformation lab (Exercise 16).
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1pt
4pts
A) Which sector is the control intended to demonstrate that transformation and not conjugation is
occurring?
B) What is the next step in the experiment?
C) Do you expect the experiment to work? Explain.
14. Identify the labeled parts of the microscope, and describe the function for each labeled part. 4pts
A.
B.
C.
D.
15. Which student (A or B) has demonstrated aseptic technique in transferring sterile broth?
1pt
16. A Kirby-Bauer Test was performed on a sample from a patient sick with a bacterial
3pts
infection caused by Staphylococcus aureus. (Both plates contain S. aureus from the infection site.)
S10=Streptomycin
P10=Penicillin
E15=Erythromycin
C30=Chloramphenicol
TE30=Tetracycline
SXT=Sulfonamides
List EACH antibiotic you could choose for antibiotic therapy, based on this test.
17. Which organism produces indole?
1pt
18. This TSY plate is from the skin flora lab (Exercise 22) and was incubated aerobically. 6pts
Name one genus of bacteria that can grow on this plate and is commonly found on the skin.
A yellow-colored colony that yielded Gram-positive cocci was isolated from this plate and
further studied using the following tests. Interpret the results for each test.
Test A: Agar Shake Tube (‘deep’): _____________________________________ (be very specific!)
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Test B: Bromcresol purple agar slant: ___________________________________
Test C: Mannitol salt agar: ___________________________________________
What is the likely organism, based on these results? Give both the generic and the specific name. Do
not abbreviate.
19. This plate contains a pure culture of an unknown organism. Test this organism for catalase
expression. Do not add catalase reagent directly to the plate; rather, transfer some cells to a glass slide.
Wash and dry the slide when you are finished.
2pts
Interpret the test: ________________
20. In a viable cell count experiment, you plated 100l of each cell dilution. What is the concentration of
the original, undiluted cell suspension? For full credit, include the correct units.
3pts
Your answer: ________________________
21.
You have a broth culture that contains of 5.3 x 107 cells/ml. You want to dilute it to obtain a
countable number of organisms on a plate. Use this area for scratch paper, and answer the
questions below.
3pts
A) What is the dilution factor of the tube that will yield a countable plate? ___________
B) What volume of this dilution will you add to the plate? ____________
C) How many colonies do you expect to see? ___________
22. Which growth medium(a) would you use for the following purposes? (Note that you can
select a particular growth medium for more than one answer, a given answer may require you to
write down multiple growth media, and it’s possible some media will not be used to answer any
of the questions).
7pts
A. To select for halophiles:
B. To select for Gram-negative organisms:
C. To identify and collect an auxotroph for further study:
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D. To differentiate types of hemolysis:
E. To distinguish between Micrococcus and Staphylococcus:
23.
A) Does this slant contain a mixture of species? How can you tell? (Can you tell?)
3pts
B) List two techniques you could perform that would help you confirm that it is a pure culture.
1. _________________________
24.
2. ___________________________
Interpret these tests (each contains a pure culture):
4pts
MR test: _____________________
Glucose fermentation test: _____________________
Is it possible both tests contain the same organism? Why or why not?
25. These are two MacConkey agar plates inoculated with different organisms. Based on the growth on
the plates, list two things you can determine about each organism.
4pts
Organism A:
Organism B:
26. Use the chart to interpret this multiple tube fermentation assay. Include the correct units!
3pts
27. Which plate demonstrates the best streaking technique? Explain your reasoning.
2pts
28. Describe the oxygen requirements for these organisms. Be specific!
4pts
Organism A:
Organism B:
Organism C:
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Which organism(s) is/are likely to grow on an agar plate in an anaerobe jar?
29. Does the brilliant green lactose bile test correlate with the LES Endo plate results? Explain. 4pts
What information can the broth give you that the plate cannot tell you?
Why do we include bile salts in the brilliant green lactose bile broth?
30. Choose any microscope along the back row to perform a Gram stain. Find the image using the oil
immersion lens, and fill out the following questions. After you have interpreted the results, raise your
hand to have the instructor look at your Gram stain and initial below. (All bacteria samples are pure
cultures.)
3pts
Gram reaction _________________
Morphology ________________
Arrangement __________________
Instructor initials ________________
31. List the reagents necessary for the Gram stain in the order you would use them.
Include the function of each reagent.
8pts
A.
B.
C.
D.
32.
Label a TSA plate with your full name (not just initials) and streak the plate for isolated colonies.
Place your plate in the collection bin when finished.
2pts
33.
Use this station as you see fit.
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