Chapter 6

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Chapter 6 review questions

In the figure, which line best depicts a facultative anaerobe in the absence of O2?
a
b
c

b. middle

In the figure, which line best illustrates a mesophile at 5°C above its optimum temperature?
a
b
c

B. middle

In the figure ,which line best depicts an obligate anaerobe in the presence of O2?
A
B
C

C. Bottom

In the figure, which line best depicts a mesophile with an optimum temperature of 35°C incubated at 40°C.
A
B
C

B. Middle

In the figure, which line shows the growth of an obligate aerobe incubated anaerobically?
A
B
C

C. Bottom

In the figure, which line best illustrates the growth of a facultative anaerobe incubated aerobically?
A
B
C

A. Top

In the figure, which line best depicts a catalase-negative cell incubated aerobically?
A
B
C

C. Bottom

Micrococci are facultative halophiles. In the figure, which line best depicts the growth of Micrococcus luteus in a nutrient medium containing 7.5% NaCl?
a
b
c

B. Middle

In the figure, which line best depicts a psychrophile incubated at room temperature?
a
b
c

C. Bottom

In the figure, which line best depicts a psychrotroph incubated at 0°C?
a
b
c

B. Middle

n the figure, which line best depicts Neisseria gonorrhoeae when growing inside the human body?
a
b
c

A. Top

The addition of which of the following to a culture medium will neutralize acids?
Sugars
Carbon
pH
Heat
Buffers

Buffers

Salts and sugars work to preserve foods by creating a
Hypertonic environment.
Lower osmotic pressure.
Lower pH.
Hypotonic environment.
Depletion of nutrients.

Hypertonic Environment

The term facultative anaerobe refers to an organism that
Requires less oxygen than is present in air.
Prefers to grow without oxygen.
Uses oxygen or grows without oxygen.
Doesn't use oxygen but tolerates it.
Is killed by oxygen.

Uses oxygen or grows without oxygen

Which of the following is an advantage of the standard plate count?
Requires incubation time
Chemical and physical requirements are determined by media and incubation.
Cannot be used to count bacteria in food
Determines the number of viable cells
Can readily count cells that form aggregates

Determines the number of viable cells

Which of the following is an advantage of the direct microscopic count?
Sample volume is unknown.
Can readily count organisms that are motile
Requires a large number of cells
Requires no incubation time
Enumerates dead cells

Requires no incubation time

Which of the following is NOT used to determine metabolic activity?
NO−2 produced from the electron transport chain
CO2 produced from the Krebs cycle
Decreased dissolved oxygen
Turbidity
Acid production from fermentation

Turbidity

Thirty-six colonies grew in nutrient agar from 1.0 ml of undiluted sample in a standard plate count. How many cells were in the original sample?
9
72
18
4
36

36

In the figure, which section shows a growth phase where the number of cells dying equals the number of cells dividing?
a
b
c
d
a and c

C. Middle

In the figure, which sections of the graph illustrate a logarithmic change in cell numbers?
a and c
b and d
a and b
c and d
b only

B & D upper left and upper right

Most bacteria grow best at pH
7.
5.
9.
14.
1.

7

The figure shows three containers of water connected by tubes. A selectively permeable membrane divides each tube. Solutes are added to each container to give final concentrations of 5% NaCl in (a); 10% NaCl in (b); and 5% sucrose in (c). When the experiment is first set up, the initial movement of water will be:
A. a to b; b to c; c to a.
B. a to b; c to b; c to a.
C. b to a; b to c; c to a.
D. a to c; c to b; c to a.
E. a to c; b to c; c to a.

B. a to b; c to b; c to a
mid - left; right - left; right - mid

A culture medium on which only gram-positive organisms grow and a yellow halo surrounds Staphylococcus aureus colonies is called a(n)
A) selective medium.
B) differential medium.
C) enrichment culture.
D) selective medium and differential medium.
E) enrichment culture and differential medium.

D) selective medium and differential medium

A culture medium consisting of agar, human blood, and beef heart is a
Differential medium.
Reducing medium.
Complex medium.
Selective medium.
Chemically defined medium.

Complex medium

Which of the following pairs is mismatched?
Psychrophile - growth at 15°C
Thermophile - growth at 37°C
Psychrotroph - growth at 0°C
Hyperthermophiles - growth at 100°C
Mesophile - growth at 25°C

Thermophile - growth at 37C

During which growth phase will gram-positive bacteria be most susceptible to penicillin?
Log phase
Lag phase
Stationary phase
Death phase
The culture is equally susceptible during all phases.

Log Phase

Which of the following is the best definition of generation time?
The length of time needed for a cell to divide
The duration of log phase
The length of time needed for lag phase
The time needed for nuclear division
The minimum rate of doubling

The length of time needed for a cell to divide

Which of the following is NOT a direct method to measure microbial growth?
Metabolic activity
Standard plate count
MPN
Filtration
Direct microscopic count

Metabolic activity

Which group of microorganisms is most likely to spoil a freshwater trout preserved with salt?
Hyperthermophiles
Anaerobes
Thermophiles
Facultative halophiles
Psychrophiles

Facultative Halophiles

Which of the following is an organic growth factor?
NAD+
Peptone
H2O
Glucose
NH4H2PO4

NAD+

Which of the following is an example of a metabolic activity that could be used to measure microbial growth?
MPN
Direct microscopic count
Glucose consumption
Standard plate count
Turbidity

Glucose consumption

An experiment began with 4 cells and ended with 128 cells. How many generations did the cells go through?
6
5
32
64
4

5

Three cells with generation times of 30 minutes are inoculated into a culture medium. How many cells are there after 5 hours?
A) 48
B) 243
C) 16
D) 1024
E) 3 × 210

E) 3 x 210

In the figure, in which tube are microaerophiles growing?
a
b
c
d
e

E gathered in the middle

In the figure, in which tube are facultative anaerobes growing?
a
b
c
d
e

B. mixed but most at the top

In one hospital, Pseudomonas aeruginosa serotype 10 infected the biliary tract of 10% of 1300 patients who underwent gastrointestinal endoscopic procedures. After each use, endoscopes were washed with an automatic reprocessor that flushed detergent and glutaraldehyde through the endoscopes, followed by a tap water rinse. P. aeruginosa 10 was not isolated from the detergent, glutaraldehyde, or tap water. What was the source of the infections?
A) Bacterial cell walls in the water
B) Contaminated disinfectant
C) A biofilm in the reprocessor
D) Fecal contamination of the bile ducts

C) A biofilm in the reprocessor

Medium A Medium B Medium C
Na2HPO4 Tide detergent Glucose
KH2PO4 Na2HPO4 Peptone
MgSO4 KH2PO4 (NH4)2SO4
CaCl2 MgSO4 KH2PO2
NaHCO3 (NH4)2SO4 Na2HPO4
In the table, which medium (media) is (are) chemically defined?
A
B
C
A and B
A and C

A

Medium A Medium B Medium C
Na2HPO4 Tide detergent Glucose
KH2PO4 Na2HPO4 Peptone
MgSO4 KH2PO4 (NH4)2SO4
CaCl2 MgSO4 KH2PO2
NaHCO3 (NH4)2SO4 Na2HPO4

In the table, in which medium would an autotroph grow?
A
B
C
A and B
A and C

A

Assume you inoculated 100 cells into 100 ml of nutrient broth. You then inoculated 100 cells of the same species into 200 ml of nutrient broth. After incubation for 24 hours, you should have
More cells in the 200 ml.
More cells in the 100 ml.
The same number of cells in both.

The same number of cells in both

The source of nutrients in nutrient agar is
Nutrient.
Peptone and NaCl.
Peptone and beef extract.
Agar.
All of the above.

Peptone and beef extract

Which enzyme catalyzes the reaction: O−2+O−2+2H+→H2O2+O2?
Superoxide dismutase
Oxidase
Peroxidase
Catalase

Superoxide dismutase

Which enzyme catalyzes the reaction: 2H2O2→2H2O+O2?
Superoxide dismutase
Peroxidase
Catalase
Oxidase

Catalase

Which enzyme catalyzes the reaction: H2O2+2H+→2H2O?
Catalase
Peroxidase
Superoxide dismutase
Oxidase

Peroxidase

The following data show growth of two bacteria on different media.

Amount of Growth
Staphylococcus aureus Streptococcus pyogenes
Nutrient agar ++ ++
Nutrient agar
+ 7.5% NaCl + -

The data in the table indicate that S. aureus is a(n)
Halophile.
Facultative anaerobe.
Aerobe.
Facultative halophile.
Mesophile.

Facultative Halophile

Patients with indwelling catheters are susceptible to infections because
Infections can be transmitted from other people.
Bacteria cause infections.
Their immune systems are weakened.
Injected solutions are contaminated.
Biofilms develop on catheters.

Biofilms develop on catheters

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