Nester's Microbiology: A Human Perspective

Denise Anderson, Sarah Salm, Deborah Allen

Chapter 4

Dynamics of Microbial Growth - all with Video Answers

Educators

Chapter Questions

Problem 1

If there are $10^{3}$ cells per $\mathrm{mL}$ at the middle of log phase, and the generation time of the cells is 30 minutes, how many cells will there be 2 hours later?
a) $2 \times 10^{3}$
b) $4 \times 10^{3}$
c) $8 \times 10^{3}$
d) $1.6 \times 10^{4}$
e) $1 \times 10^{7}$

Sylvia Puglisi

Sylvia Puglisi

Numerade Educator

Problem 2

Compared with their growth in the laboratory, bacteria in nature generally grow
a) more slowly.
b) faster.
c) at the same rate.

Sylvia Puglisi

Numerade Educator

Problem 3

Cells are most sensitive to penicillin during which phase of the growth curve?
a) Lag
b) Exponential
c) Stationary
d) Death
e) More than one of these.

Sylvia Puglisi

Numerade Educator

Problem 4

Which best describes the intestinal tract?
a) an open system with a chemically defined medium
b) an open system with a complex medium
c) a closed system with a chemically defined medium
d) a closed system with a complex medium

Sylvia Puglisi

Numerade Educator

Problem 5

$E$ coli, a facultative anaerobe, is grown for 24 hours on the same type of solid medium, but under two different conditions: one aerobic, the other anaerobic. The size of the colonies would be
a) the same under both conditions.
b) larger when grown under aerobic conditions.
c) larger when grown under anaerobic conditions.

Sylvia Puglisi

Numerade Educator

Problem 6

The generation time of a bacterium was measured at two different temperatures. Which results would be expected of a thermophile?
a) 20 minutes at $10^{\circ} \mathrm{C} ; 220$ minutes at $37^{\circ} \mathrm{C}$
b) 220 minutes at $10^{\circ} \mathrm{C} ; 20$ minutes at $37^{\circ} \mathrm{C}$
c) no growth at $10^{\circ} \mathrm{C} ; 20$ minutes at $37^{\circ} \mathrm{C}$
d) 20 minutes at $45^{\circ} \mathrm{C} ; 220$ minutes at $65^{\circ} \mathrm{C}$
e) 220 minutes at $37^{\circ} \mathrm{C} ; 20$ minutes at $65^{\circ} \mathrm{C}$

Sylvia Puglisi

Numerade Educator

Problem 7

Which of the following is false?
a) $E .$ coli grows faster in nutrient broth than in glucose-salts medium.
b) Organisms require nitrogen to make amino acids
c) Some eukaryotes can fix $\mathrm{N}_{2}$
d) An organism that grows on ham is halotolerant.
e) Blood agar is used to detect hemolysis.

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Numerade Educator

Problem 8

If the $\mathrm{pH}$ indicator were left out of MacConkey agar, the medium would be
a) complex.
b) differential.
c) defined.
d) defined and differential.
e) complex and differential.

Sylvia Puglisi

Numerade Educator

Problem 9

A soil sample is placed in liquid and the number of bacteria in the sample determined in two ways: (1) colony count and (2) direct microscopic count. How would the results compare?
a) Methods 1 and 2 would give approximately the same results.
b) Many more bacteria would be estimated by method 1
c) Many more bacteria would be estimated by method 2
d) Depending on the soil sample, sometimes method 1 would be higher and sometimes method 2 would be higher

Sylvia Puglisi

Numerade Educator

Problem 10

If the concentration of $E .$ coli in a broth is between $10^{4}$ and $10^{6}$ cells per $\mathrm{mL},$ the best way determine the precise number of living cells in the sample, would be to
a) use a counting chamber.
b) plate out an appropriate dilution of the sample on nutrient agar.
c) determine cell number by using a spectrophotometer.
d) Any of these three methods would be satisfactory.
e) None of these three methods would be satisfactory.

Sylvia Puglisi

Numerade Educator