Deck 6: Microbial Growth

Question 1

Which of the following is not used to determine metabolic activity?

A) Turbidity.
B) Acid production from fermentation.
C) CO₂ produced from the Krebs cycle.
D) Decreased dissolved oxygen.
E) NO₂^- produced from the electron transport chain.

Answer 1

Turbidity.

Question 2

Which of the following is the best definition of generation time?

A) The time it takes for nuclear division.
B) The length of time it takes for lag phase.
C) The duration of log phase.
D) The length of time it takes for a cell to divide.
E) The minimum rate of doubling.

Answer 2

D

Question 3

Figure 6.1

Micrococci are facultative halophiles. In Figure 6.1, which line best depicts the growth of M. luteus
In a nutrient medium containing 7.5% NaCl?

A) a
B) b
C) c

Answer 3

B

Question 4

All of the following are direct methods to measure microbial growth except

A) MPN.
B) Direct microscopic count.
C) Standard plate count.
D) Metabolic activity.
E) Filtration.

Question 5

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

A) Chemically defined medium.
B) Reducing medium.
C) Selective medium.
D) Complex medium.
E) Differential medium.

Question 6

Figure 6.1

In Figure 6.1, which line best depicts a catalase- negative cell incubated aerobically?

A) a
B) b
C) c

Question 7

Figure 6.2

In Figure 6.2, which section shows a growth phase where the number of cells dying equals the number of cells dividing?

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

Question 8

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

A) Thermophiles
B) Anaerobes
C) Halophiles
D) Psychrophiles
E) None of the above

Question 9

Assume you inoculated 100 cells into 100 ml nutrient broth. You then inoculated 100 cells of the same species into 200 ml nutrient broth. After incubation for 24 hr, you should have

A) More cells in the 200 ml.
B) More cells in the 100 ml.
C) The same number of cells in both.

Question 10

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

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

Question 11

Which enzyme catalyzes the reaction: H?O?+?H+ ??H?O?

A) Superoxide dismutase
B) Oxidase
C) Peroxidase
D) Catalase
E) None of the above

Question 12

Figure 6.1

In Figure 6.1, which line best depicts a mesophile with an optimum temperature of 35°C incubated at 40°C?

A) a
B) b
C) c

Question 13

Which of the following is an example of a metabolic activity that could be used to measure microbial growth?

A) Standard plate count
B) Direct microscopic count
C) Glucose consumption
D) MPN
E) Turbidity

Question 14

Which organism produces catalase and superoxide dismutase?

A) Aerobe
B) Obligate anaerobe
C) Aerotolerant anaerobe

Question 15

The source of nutrients in nutrient agar is

A) Peptone and beef extract.
B) Nutrient.
C) Agar.
D) Peptone and NaCl.
E) All of the above.

Question 16

Producers in the hydrothermal vents on the ocean floor use CO? for their carbon source and what for energy?

A) Organic molecules
B) Sulfide
C) Carbon dioxide
D) Light
E) None of the above

Question 17

Figure 6.1

In Figure 6.1, which line best depicts a psychrotroph incubated at 0°C?

A) a
B) b
C) c

Question 18

Three cells with generation times of 30 minutes are inoculated into a culture medium. How many cells are there after 5 hours?

A) 16
B) 48
C) 3 × 2¹⁰
D) 1024
E) 243

Question 19

Which organism is killed by atmospheric O₂?

A) Obligate anaerobe
B) Aerotolerant anaerobe
C) Aerobe

Question 20

The addition of which of the following to a culture medium will neutralize acids?

A) pH
B) Heat
C) Sugars
D) Carbon
E) Buffers

Question 21

Which enzyme catalyzes the reaction: 2H?O? ?2H?O + O??

A) Catalase
B) Peroxidase
C) Oxidase
D) Superoxide dismutase
E) None of the above

Question 22

Figure 6.1

In Figure 6.1, which line shows the growth of an obligate aerobe incubated anaerobically?

A) a
B) b
C) c

Question 23

Which of the following is not a disadvantage of the direct microscopic count?

A) No incubation time.
B) Large number of cells is required.
C) Sample volume is unknown.
D) Enumerates dead cells.
E) Some organisms are motile.

Question 24

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?

A) 9
B) 4
C) 72
D) 36
E) 18

Question 25

Figure 6.3

Figure 6.3 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 c; c to b; c to a.
B) a to b; c to b; c to a.
C) a to b; b to c; c to a.
D) b to a; b to c; c to a.
E) a to c; b to c; c to a.

Question 26

The term facultative anaerobe refers to an organism that

A) Is killed by oxygen.
B) Doesn't use oxygen but tolerates it.
C) Uses oxygen or grows without oxygen.
D) Prefers to grow without oxygen.
E) Requires less oxygen than is present in air.

Question 27

Figure 6.1

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

A) a
B) b
C) c

Question 28

Table 6.1
Below are three different culture media. $\begin{array}{lll}\underline{\text { Medium A }} & \underline{\text {Medium B} } &\underline{ \text { Medium C }}\\\mathrm{Na}_{2} \mathrm{HPO}_{4} & \text { Tide detergent } & \text { Glucose } \\\mathrm{KH}_{2} \mathrm{PO}_{4} & \mathrm{Na}_{2} \mathrm{HPO}_{4} & \text { Peptone }\\\mathrm{MgSO}_{4} & \mathrm{KH}_{2} \mathrm{PO}_{4} & \left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4} \\\mathrm{CaCl}_{2} & \mathrm{MgSO}_{4} & \mathrm{KH}_{2} \mathrm{PO}_{2} \\\mathrm{NaHCO}_{3} & \left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4} & \mathrm{Na}_{2} \mathrm{HPO}_{4}\end{array}$

-In Table 6.1, which medium (media) is (are) chemically defined?

A) A
B) B
C) A and B
D) A and C
E) None of the above

Question 29

Figure 6.1

In Figure 6.1 ,which line best depicts an obligate anaerobe in the presence of O₂?

A) a
B) b
C) c

Question 30

Figure 6.1

In Figure 6.1, which line best illustrates the growth of a facultative anaerobe incubated aerobically?

A) a
B) b
C) c

Question 31

Which of the following is not a disadvantage of the standard plate count?

A) Cells may form aggregates.
B) Requires incubation time.
C) Chemical and physical requirements are determined by media and incubation.
D) Determines viable cells.
E) None of the above.

Question 32

Table 6.1
Below are three different culture media. $\begin{array}{lll}\underline{\text { Medium A }} & \underline{\text {Medium B }} &\underline{ \text { Medium C }}\\\mathrm{Na}_{2} \mathrm{HPO}_{4} & \text { Tide detergent } & \text { Glucose } \\\mathrm{KH}_{2} \mathrm{PO}_{4} & \mathrm{Na}_{2} \mathrm{HPO}_{4} & \text { Peptone }\\\mathrm{MgSO}_{4} & \mathrm{KH}_{2} \mathrm{PO}_{4} & \left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4} \\\mathrm{CaCl}_{2} & \mathrm{MgSO}_{4} & \mathrm{KH}_{2} \mathrm{PO}_{2} \\\mathrm{NaHCO}_{3} & \left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4} & \mathrm{Na}_{2} \mathrm{HPO}_{4}\end{array}$

-In Table, 6.1, in which medium would an autotroph grow?

A) A
B) B
C) A and B
D) A and C
E) None of the above

Question 33

Table 6.2
The following data show growth of two bacteria on different media. $\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\text { Amount of Growth }$
$\begin{array}{ll}&\text { Staphylococcus aureus }&\text { Streptococcus pyogenes }\\\text { Nutrient agar }&++&++\\\text { Nutrient agar }+7.5 \%\\\mathrm{NaCl}&+&-\end{array}$


-The data in Table 6.2 indicate that S. aureus is a(n)

A) Facultative anaerobe.
B) Facultative halophile.
C) Halophile.
D) Aerobe.
E) Mesophile.

Question 34

Figure 6.1

In Figure 6.1, which line best illustrates a mesophile at 5°C above its optimum temperature?

A) a
B) b
C) c

Question 35

During which growth phase will gram- positive bacteria be most susceptible to penicillin?

A) Log phase
B) Stationary phase
C) Lag phase
D) Death phase
E) The culture is equally susceptible during all phases.

Question 36

Figure 6.1

In Figure 6.1, which line best depicts a psychrophile incubated at room temperature?

A) a
B) b
C) c

Question 37

Figure 6.1

In Figure 6.1, which line best depicts Neisseria gonorrhoeae when growing inside the human body?

A) a
B) b
C) c

Question 38

Which of the following pairs is mismatched?

A) Psychrotroph - growth at 0°C
B) Thermophile - growth at 37°C
C) Psychrophile - growth at 15°C
D) Mesophile - growth at 25°C
E) None of the above

Question 39

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) B and C.
E) A and B.

Question 40

Most bacteria grow best at pH

A) 5.
B) 7.
C) 14.
D) 9.
E) 1.

Question 41

Figure 6.2

In Figure 6.2, which sections of the graph illustrate a logarithmic change in cell numbers?

A) b and d
B) c and d
C) a and b
D) a and c
E) b only

Question 42

Salts and sugars work to preserve foods by creating a

A) Hypotonic environment.
B) Lower osmotic pressure.
C) Lower pH.
D) Hypertonic environment.
E) Depletion of nutrients.