Question 1

Which of the following pairs of microbe classification terms and optimal growth temperatures is mismatched?

Accepted Answer

A)  psychrotroph - growth at 20-30°C
B)  thermophile - growth at 37°C
C)  mesophile - growth at 25-40°C
D)  psychrophile - growth at 15°C
E)  hyperthermophiles - growth at greater than 80°C

Question 2

A culture medium consisting of agar,peptone,and beef heart is a

Accepted Answer

A)  chemically defined medium.
B)  complex medium.
C)  selective medium.
D)  differential medium.
E)  reducing medium.

Question 3

If cells are grown in media containing amino acids labeled with radioactive nitrogen (¹⁵N) ,most of the radioactivity will be found in the cells'

Accepted Answer

A)  DNA.
B)  proteins.
C)  phospholipids.
D)  DNA and proteins.
E)  DNA and phospholipids. D

Question 4

Patients with indwelling catheters (long-term tubes inserted into body orifices for drainage,such as through the urethra and into the urinary bladder) are susceptible to infections because

Accepted Answer

A)  injected solutions are contaminated.
B)  their immune systems are weakened.
C)  infections can be transmitted from other people.
D)  biofilms develop on catheters.
E)  bacteria cause infections.

Question 5

A sample of milk is tested for its bacterial content in a plate count assay.A one-milliliter sample of the milk is diluted in a 1:10 dilution series.One milliliter of the third dilution tube is plated in a pour plate.After incubation,the plate has 54 colonies,indicating that the original milk sample contained

Accepted Answer

A)  54 cells per milliliter.
B)  540 cells per milliliter.
C)  5,400 cells per milliliter.
D)  54,000 cells per milliliter.
E)  540,000 cells per milliliter.

Question 6

A patient with a heart pacemaker received antibiotic therapy for streptococcal bacteremia (bacteria in the blood).One month later,he was treated for recurrence of the bacteremia.When he returned six weeks later,again with bacteremia,the physician recommended replacing the pacemaker.Why did this cure his condition?

Accepted Answer

The patient's recurring episodes of streptococcal bacteremia, despite antibiotic therapy, suggest that the source of the bacterial infection was not being adequately addressed. In cases where a patient has an implanted medical device, such as a heart pacemaker, there is a risk that the device can become a nidus for infection. This means that bacteria can adhere to the device and form a biofilm, which is a complex aggregation of microorganisms marked by the excretion of a protective and adhesive matrix.

Biofilms are particularly concerning because they can be very resistant to antibiotics. The protective matrix and the altered state of the bacteria within the biofilm can prevent antibiotics from effectively killing the bacteria. As a result, even after antibiotic treatment, the bacteria can persist on the device and re-enter the bloodstream, leading to recurrent infections.

When a patient with an implanted device experiences repeated infections despite appropriate antibiotic therapy, it raises the suspicion that the device itself is infected. In such cases, the most definitive treatment is often to remove the infected device and replace it with a new one. This is because it is extremely difficult, if not impossible, to completely eradicate the bacteria from the device with antibiotics alone.

By recommending the replacement of the pacemaker, the physician was targeting the likely source of the recurrent infections. After the infected pacemaker was removed and a new one was implanted, the source of the streptococcal bacteremia was eliminated. This, combined with a course of antibiotics to clear any remaining bacteria from the bloodstream, would have cured the patient's condition by removing both the source of the infection and the infection itself.

It is important to note that the decision to replace an infected pacemaker is not taken lightly due to the risks associated with surgery and the potential complications of the procedure. However, when the benefits of removing a source of persistent infection outweigh the risks, pacemaker replacement becomes a necessary and curative intervention.

Question 7

Most bacteria reproduce by

Accepted Answer

A)  aerial hyphae.
B)  fragmentation.
C)  mitosis.
D)  binary fission.
E)  budding.

Question 8

In performing a ten-fold dilutions series from a sample containing 10,000 bacteria per milliliter,the fourth tube in the dilution series will have 10 cells per milliliter.

Accepted Answer

A) True 
 B)False

Question 9

Consider a culture medium on which only gram-positive organisms such as Staphylococcus aureus colonies can grow due to an elevated NaCl level.A yellow halo surrounds the growth,indicating the bacterium fermented a sugar in the medium,decreasing the pH as a result and changing the color of a pH indicator chemical.This type of medium would be referred to as a(n)

Accepted Answer

A)  selective medium.
B)  differential medium.
C)  enrichment culture.
D)  selective and differential medium.
E)  differential and enrichment culture.

Question 10

Figure 6.1
 
-Figure 6.1,which line best depicts a facultative anaerobe in the absence of O₂?

Accepted Answer

A)  a
B)  b
C)  c

Question 11

Pure cultures can easily be obtained on streak plates,even if the desired bacteria are present in very low concentrations in the initial culture broth.

Accepted Answer

A) True 
 B)False

Question 12

Most pathogenic bacteria are thermophiles.

Accepted Answer

A) True 
 B)False

Question 13

Figure 6.3
 
-In Figure 6.3,which tube shows the expected growth pattern for a facultative anaerobe?

Accepted Answer

A)  a
B)  b
C)  c
D)  d
E)  e

Question 14

The ________ method is used to indirectly measure microbial growth of filamentous bacteria and molds.

Accepted Answer

A)  metabolic activity
B)  dry weight
C)  pour plate
D)  spread plate
E)  turbidity measurement

Question 15

Which of the following is an advantage of the direct microscopic count?

Accepted Answer

A)  can readily count organisms that are motile
B)  can easily distinguish live from dead cells
C)  requires no incubation time
D)  sample volume is unknown
E)  requires a large number of cells

Question 16

A sample of raw,unpasteurized milk is tested for its bacterial content in a plate count assay.A one-milliliter sample of the milk is diluted in a 1:10 dilution series.One milliliter of the third dilution tube is plated in a pour plate.After incubation,the plate has approximately 500 colonies,indicating that the original milk sample contained

Accepted Answer

A)  500 cells per milliliter.
B)  5,000 cells per milliliter.
C)  50,000 cells per milliliter.
D)  500,000 cells per milliliter.
E)  The answer cannot be determined reliably with the information given.

Question 17

A sample of well water is tested for its bacterial content in a plate count assay.A one-milliliter sample of the water is diluted in a 1:10 dilution series.One milliliter of the fourth dilution tube is plated in a pour plate.After incubation,the plate has 83 colonies,indicating that the original water sample contained

Accepted Answer

A)  83 cells per milliliter.
B)  830 cells per milliliter.
C)  8,300 cells per milliliter.
D)  83,000 cells per milliliter.
E)  830,000 cells per milliliter. E

Question 18

Which enzyme catalyzes the reaction: H₂O₂ + 2H⁺ → 2H₂O?

Accepted Answer

A)  catalase
B)  oxidase
C)  peroxidase
D)  superoxide dismutase

Question 19

Which group of microorganisms is most likely to spoil a freshwater trout preserved with salt?

Accepted Answer

A)  psychrophiles
B)  facultative halophiles
C)  anaerobes
D)  thermophiles
E)  hyperthermophiles

Question 20

An experiment began with 4 cells in log phase and ended with 128 cells.How many generations did the cells go through?

Accepted Answer

A)  64
B)  32
C)  6
D)  5
E)  4

Exam 6: Microbial Growth

Which of the following pairs of microbe classification terms and optimal growth temperatures is mismatched?

Correct Answer
verified

A culture medium consisting of agar,peptone,and beef heart is a

Correct Answer
verified

If cells are grown in media containing amino acids labeled with radioactive nitrogen (¹⁵N) ,most of the radioactivity will be found in the cells'

Correct Answer
verified
D

Patients with indwelling catheters (long-term tubes inserted into body orifices for drainage,such as through the urethra and into the urinary bladder) are susceptible to infections because

Correct Answer
verified

Correct Answer
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Most bacteria reproduce by

Correct Answer
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In performing a ten-fold dilutions series from a sample containing 10,000 bacteria per milliliter,the fourth tube in the dilution series will have 10 cells per milliliter.

Correct Answer
verified

Correct Answer
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Figure 6.1 -Figure 6.1,which line best depicts a facultative anaerobe in the absence of O₂?

Correct Answer
verified

Pure cultures can easily be obtained on streak plates,even if the desired bacteria are present in very low concentrations in the initial culture broth.

Correct Answer
verified

Most pathogenic bacteria are thermophiles.

Correct Answer
verified

Figure 6.3 -In Figure 6.3,which tube shows the expected growth pattern for a facultative anaerobe?

Correct Answer
verified

The ________ method is used to indirectly measure microbial growth of filamentous bacteria and molds.

Correct Answer
verified

Which of the following is an advantage of the direct microscopic count?

Correct Answer
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Correct Answer
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Correct Answer
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E

Which enzyme catalyzes the reaction: H₂O₂ + 2H⁺ → 2H₂O?

Correct Answer
verified

Which group of microorganisms is most likely to spoil a freshwater trout preserved with salt?

Correct Answer
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An experiment began with 4 cells in log phase and ended with 128 cells.How many generations did the cells go through?

Correct Answer
verified

Exam 6: Microbial Growth

Which of the following pairs of microbe classification terms and optimal growth temperatures is mismatched?

Correct AnswerverifiedShow Answer

A culture medium consisting of agar,peptone,and beef heart is a

Correct AnswerverifiedShow Answer

If cells are grown in media containing amino acids labeled with radioactive nitrogen (¹⁵N) ,most of the radioactivity will be found in the cells'

Correct AnswerverifiedD

Patients with indwelling catheters (long-term tubes inserted into body orifices for drainage,such as through the urethra and into the urinary bladder) are susceptible to infections because

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

Most bacteria reproduce by

Correct AnswerverifiedShow Answer

In performing a ten-fold dilutions series from a sample containing 10,000 bacteria per milliliter,the fourth tube in the dilution series will have 10 cells per milliliter.

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

Figure 6.1 -Figure 6.1,which line best depicts a facultative anaerobe in the absence of O₂?

Correct AnswerverifiedShow Answer

Pure cultures can easily be obtained on streak plates,even if the desired bacteria are present in very low concentrations in the initial culture broth.

Correct AnswerverifiedShow Answer

Most pathogenic bacteria are thermophiles.

Correct AnswerverifiedShow Answer

Figure 6.3 -In Figure 6.3,which tube shows the expected growth pattern for a facultative anaerobe?

Correct AnswerverifiedShow Answer

The ________ method is used to indirectly measure microbial growth of filamentous bacteria and molds.

Correct AnswerverifiedShow Answer

Which of the following is an advantage of the direct microscopic count?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

Correct AnswerverifiedE

Which enzyme catalyzes the reaction: H₂O₂ + 2H⁺ → 2H₂O?

Correct AnswerverifiedShow Answer

Which group of microorganisms is most likely to spoil a freshwater trout preserved with salt?

Correct AnswerverifiedShow Answer

An experiment began with 4 cells in log phase and ended with 128 cells.How many generations did the cells go through?

Correct AnswerverifiedShow Answer

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D

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E

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