Microbiology
Stavney
Name
Lab Quiz II
25 points total. Use Scantron answer form for Questions 1-13. Then fill in the answers for the Short
Answer Questions that follow question 13. Write your name, date, class, and Q2 on your Scantron form,
and the first three letters of your last name on the back upper side, near question 51. Insert your
Scantron into these questions, put your name at the upper left, and turn it in.
1. Which of the following can you determine from a streak plate, made from transferring a loopful of
material from a broth or slant to a nutrient agar plate and streaking for isolation?
a. You can determine if the bacteria are gram positive or gram negative
b. You can determine if the bacteria are rods, cocci, or spirilla
c. You can determine the cellular arrangement of the cells
d. You can determine the number of colony forming units per ml of the broth or slant
e. You can determine whether your original culture is a pure or mixed culture
2. What gas combines with and removes oxygen from the inside of an anaerobic Brewer jar?
a. water vapor
b. carbon dioxide
c. hydrogen
d. oxygen
e. hydrogen sulfide
3. The purpose of placing a strip of methylene blue into an anaerobic jar is to determine:
a. Whether any carbon dioxide was present in the jar
b. Whether any water vapor was in the jar
c. Whether any oxygen was in the jar
d. Whether anaerobic bacteria grew successfully
e. Whether aerobic bacteria grew successfully
4. In the test tubes above showing growth of different bacterial species in thioglycollate broth after 2448 hours of incubation, which tube (a-e) shows growth of a facultative anaerobe?
5. In the thioglycollate tubes shown above, which tubes show the growth of an organism that does not
make catalase? Answer using the letters of all the tubes that fit this description. ( If the correct answer is
"a." and "c." and "d.", fill in "acd" on your answer sheet).
Bio 250 Lab Quiz 2 pg. 1
6. Which type of organisms would be expected to grow heavily on the top with growth extending
downwards through the inoculation tunnel to the very bottom of an agar deep?
a. strict (obligate) aerobe
b. facultative anaerobe
c. strict (obligate) anaerobe
d. aerotolerant anaerobe
e. microaerophile
7. Which organism was a thermophile, according to the results of our studies in lab?
a. Escherichia coli
b. Bacillus stearothermophilus
c. Pseudomonas aeruginosa
d. Clostridium sporogenes
e. Serratia marcescens
8. Why do some bacteria grow well at pH 7 while others cannot grow at this pH?
a. The growers can produce buffers to allow them to survive at this pH
b. The growers utilize the protein in the media, which allows them to adjust the pH
c. The growers are adapted to survive at any pH
d. The non-growers lack enzymes that are functional at this pH
e. The non-growers cannot handle the oxygen levels at this pH
--------------------------------------------------------------------------------------------------------------TRUE/FALSE Answer “a” if true and “b” if false.
9. Based on our results in the laboratory, Escherichia coli is generally more tolerant of a high salt
environmental than Staphylococcus aureus is.
10. Bacteria are better at handling hypotonic environments than hypertonic ones.
11. The gas that replaces oxygen in the anaerobic (Brewer) jar is carbon dioxide.
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Bio 250 Lab Quiz 2 pg. 2
12. What dilution of the original culture
can be found in Tube III in the dilution
series shown to the left?
a. 1/100
b. 1/1000
c. 1/10,000
d. (11.1)/(108.9)
e. 1/250,000
SHORT ANSWER SECTION
Name:
A. 1pt. What is the optimum growth temperature for most mesophiles?
B. 1 pt. Name the optimal growth environment (using an approximate pH, salt concentration,
temperature, etc.) for an alkaliphile.
C. The picture below shows the growth of bacteria on a student streak plate. Each spreading series, or
“Run”, is numbered as 1, 2, 3, and 4 in order of how they were made. The arrowheads indicate the
direction of the streaking in each run. Using this diagram, critique the streaking method and answer the
following questions.
i.
2 pts. Why wasn’t better separation of colonies achieved in Run #2? Explain what was done
wrong and how it could be corrected in future streak plates.
Bio 250 Lab Quiz 2 pg. 3
ii. 2 pts. What mistake in Run #3 led to the large number of overlapping colonies that grew there?
What is the evidence that allows you to make this conclusion?
iii. 2 pts. What mistake in Run #4 led to the total lack of colonies for this run? There are a couple
possibilities – name at least one.
Bio 250 Lab Quiz 2 pg. 4
First 3 letters of last name: ____
_____ ______
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D. 5 pts. In the spread plate assay
shown to the left, the number of
colonies found in each plate is
written inside each plate. The
dilution of each tube is shown
above each tube. Chose the
appropriate plate and calculate the
number of bacteria per ml of the
original culture. SHOW ALL
YOUR WORK BELOW for full
credit.
Answer (include correct units)
Bio 250 Lab Quiz 2 pg. 5