Question 1

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?

Accepted Answer

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

Question 2

Most bacteria grow best at pH

Accepted Answer

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

Question 3

Table 6.1
Three different culture media are shown below. $\begin{array}{|l|l|l|}
\hline \text { Medium A } & \text { Medium B } & \text { Medium C } \
\hline \text { Na2H PO4 } & \text { Tide detergent } & \text { Glucose } \
\hline \text { KH2PO4 } & \text { Na2HPO4 } & \text { Peptone } \\hline \mathrm{MgSO}_{4} & \mathrm{KH}_{2} \mathrm{PO}_{4} & \left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4} \
\hline \mathrm{CaCl}_{2} & \mathrm{MgSO}_{4} & \mathrm{KH}_{2} \mathrm{PO}_{2} \
\hline \mathrm{NaHCO}_{3} & \left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4} & \mathrm{Na}_{2} \mathrm{HPO}_{4} \
\hline
\end{array}$
-In Table, 6.1, in which medium (or media) would an autotroph grow?

Accepted Answer

A)   A
B)   B
C)   C
D)   A and B
E)   A and C  A

Question 4

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

Accepted Answer

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

Question 5

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 6

Which enzyme catalyzes the reaction: 2H 2o2 → 2H2O + o2?

Accepted Answer

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

Question 7

The biosafety level (BSL) for a clinical microbiology laboratory working with potentially airborne pathogens, such as tuberculosis bacteria, is

Accepted Answer

A)   BSL-1.
B)   BSL-2.
C)   BSL-3.
D)   BSL-4.

Question 8

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

Accepted Answer

A)   psychrotroph  growth at 0°C
B)   mesophile  growth at 25°C
C)   thermophile  growth at 37°C
D)   hyperthermophiles  growth at 85°C
E)   psychrophile  growth at 15°C

Question 9

Bacterial growth refers to an increase in the numbers of cells in a bacterial culture.

Accepted Answer

A) True 
 B)False

Question 10

Which of the following elements is NOT correctly matched with its cellular function?

Accepted Answer

A)   phosphorus  used for production of carbohydrates.
B)   nitrogen  needed for amino acid synthesis
C)   sulfur  used for synthesis of thiamin and biotin
D)   phosphorus  incorporated into nucleic acids
E)   magnesium and potassium  required as cofactors for enzymes

Question 11

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

Accepted Answer

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

Question 12

Table 6.3
 $\begin{array}{|l|l|c|c|c|} 
\hline&& {\text { Generation Time }} \
\hline \text { Medium } & \text { Escherichia coli } & \begin{array}{c}
\text { Pseudomonas } \
\text { aeruginosa }
\end{array} & \text { Lactobacillus } & \text { Nitrobacter } \\hline \mathrm{NaCl}, \mathrm{NO}_{3}-, \mathrm{MgSO}_{4} & 0 & 0 & 0 & 80 \
\hline \text { Glucose } & 100 & 0 & 0 & 0 \\hline \text { Glucose, } \mathrm{NaCl}, \mathrm{PO}_{4}{ }^{3-} & 56 & 200 & 0 & 0 \
\hline \text { Glucose, } \mathrm{NaCl}, \mathrm{PO}_{4}{ }^{3-}, \mathrm{MgSO}_{4} & 43 & 100 & 0 & 0 \
\hline \text { Glucose, } \mathrm{NaCl}, \mathrm{PO}_{4}{ }^{3-}, \mathrm{MgSO}_{4}, & 28 & 40 & 0 & 0 \
8 \text { amino acids }\\hline \begin{array}{l}
\text { Glucose, } \mathrm{NaCl}_{1} \mathrm{PO}_{4}{ }^{3-}, \mathrm{MgSO}_{4} \
19 \text { amino adids }
\end{array} & 25 & 25 & 80 & 0 \
\hline
\end{array}$ Bacterial generation times for four different bacterial species were calculated in the media listed in Table 6.3. All media were prepared with pure distilled water and incubated aerobically in the light. Compare and contrast the growth requirements of the four bacteria listed above. Which of the media, if any, are chemically defined?

Accepted Answer

The answer of Table 6.3
 \(\begin{array}{|l|l|c|c|c|} 
\hline&& {\text { Generation...

Question 13

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 answer of A patient with a heart pacemaker received...

Question 14

Table 6.2 The following data show growth of two bacteria on different media.
$$\begin{array}{l}
\text { Amount of Growth }\
\begin{array} { | l | c | c | } 
\hline & \text { Staphylococcus aureus } & \text { Streptococcus pyogenes } \
\hline \text { Nutrient agar } & + + & + + \
\hline \text { Nutrient agar } + 7.5 \% \mathrm { NaCl } & + & - \
\hline
\end{array}
\end{array}$$ The data in Table 6.2 indicate that S. aureus is a(n)

Accepted Answer

A)   facultative halophile.
B)   halophile.
C)   facultative anaerobe.
D)   aerobe.
E)   mesophile.

Question 15

Agar is used as a solidifying agent in microbiological media since few bacteria can degrade it.

Accepted Answer

A) True 
 B)False

Question 16

Turbidity is an indirect measurement of bacterial growth that can be measured using a spectrophotometer.

Accepted Answer

A) True 
 B)False

Question 17

Pathogenic bacteria isolated from the respiratory or intestinal tracts of humans are

Accepted Answer

A)   strict aerobes that grow best in candle jars.
B)   capnophiles that grow best in carbon dioxide incubators.
C)   capnophiles that prefer highly oxygenated growth conditions.
D)   strict aerobes that grow best in reducing media.
E)   facultative anaerobes that require reducing media for growth.

Question 18

Which enzyme catalyzes the reaction: o2- + o2- + 2H+ → H2o2 + o2?

Accepted Answer

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

Question 19

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 20

Three cells with generation times of 60 minutes are inoculated into a culture medium. How many cells are there after 5 hours?

Accepted Answer

A)   180
B)   900
C)   15
D)   96
E)   32

Exam 6: Microbial Growth

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?

Most bacteria grow best at pH

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

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.

Which enzyme catalyzes the reaction: 2H 2o₂ → 2H₂O + o₂?

The biosafety level (BSL) for a clinical microbiology laboratory working with potentially airborne pathogens, such as tuberculosis bacteria, is

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

Bacterial growth refers to an increase in the numbers of cells in a bacterial culture.

Which of the following elements is NOT correctly matched with its cellular function?

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

Agar is used as a solidifying agent in microbiological media since few bacteria can degrade it.

Turbidity is an indirect measurement of bacterial growth that can be measured using a spectrophotometer.

Pathogenic bacteria isolated from the respiratory or intestinal tracts of humans are

Which enzyme catalyzes the reaction: o₂- + o₂- + 2H+ → H₂o₂ + o₂?

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.

Three cells with generation times of 60 minutes are inoculated into a culture medium. How many cells are there after 5 hours?