Chapter 6 Growth
3. If you found a bacterial species growing in a very hot (110oC)
hot spring that was also was very salty, how would you classify
that organism?
A.
B.
C.
D.
E.
As
As
As
As
As
a
a
a
a
a
barophilic
barophilic
halophilic
halophilic
halophilic
hyperthermophile
thermophile
mesophile
thermophile
hyperthermophile
7. Imagine that you have discovered a new bacterium that you
call Dividium tripartum because it divides into 3 daughter cells
instead of 2 like other bacteria. If you inoculated a single
cell of Dividium tripartum into some growth medium how many
bacteria would be in the flask 5 hours later, if the generation
time was 1 hour per generation?
A.
B.
C.
D.
E.
27
32
81
243
256
19. When following the growth of bacterial cultures which of the
things listed below can be monitored to track growth?
A.
B.
C.
D.
E.
Cell number
DNA
O2
Two of the above
A, B and C can all be used
26. You inoculate a flask of nutrient broth with 102 bacteria and
come back 4 hours later and find that the flask contains 106
bacteria. How many generations took place in the 4 hours?
A.
B.
C.
D.
E.
104
2100
about 19
about 13
about 17
28. Anaerobes cannot handle the presence of oxygen. Why is that?
A.
B.
C.
D.
E.
Oxygen is a requirement for growth these bacteria
Oxygen blocks respiration in these bacteria
Oxygen inhibits key enzymes needed for flagellar motility
Oxygen interferes with for twitching motility
None of the above are correct
3. The generation time for a microorganism is 30 minutes.
Starting with 3 microorganisms, it would take _______ to
obtain 200 microorganisms.
A) 1 hour
B) 2 hours
C) 3 hours
D) 4 hours
4. An obligate anaerobe
A) grows in limited levels of oxygen.
B) can tolerate small amounts of oxygen if mixed with carbon
dioxide.
C) is not killed by superoxide anions.
D) lacks superoxide dismutase.
E) contains active catalase and peroxidase to help remove traces
of oxygen.
5. Some bacteria cannot grow in pure culture.
A) True
B) False
29.
A)
B)
C)
D)
E)
Halophiles can tolerate
temperatures above 100°C.
a vitamin-depleted medium.
5%–10% NaCl.
pH < 5.5.
None of the above
39. A medium for growth of a bacterium that contains yeast or
beef extract is a(n) _______ medium.
A) defined
B) artificial
C) complex
D) semisynthetic
E) enrichment
2) What is the function of siderophores?
a) Transporting waste products out of the cell.
b) Binding iron for transport into the cell.
c) Binding glucose for transport into the cell.
d) Transporting proteins out of the cell.
e) Moving potassium into the cell for osmotic regulation.
6) What is nitrogen fixation?
a) The oxidation of nitrate to ammonia for assimilation.
b) The oxidation of ammonia to nitrate for assimilation.
c) The reduction of dinitrogen to ammonia for assimilation.
d) The reduction of nitrate to dinitrogen for assimilation.
e) The release of an amino group from an amino acid for assimilation.
13) Term that applies to a bacterium that has an absolute requirement of oxygen for growth..
a) aerobe
b) anaerobe
c) aerotolerant anaerobe
d) facultative anaerobe
e) facultative aerobe
16) What is the term for microbes that grow optimally at a pH below 5.5?
a) alkalophiles
b) psychrophiles
c) halophiles
d) acidophiles
e) barophiles
19) Term applied to microbes that grow optimally at temperatures below 15°C.
a) psychrophiles
b) barophiles
c) alkalophiles
d) mesophiles
e) halophiles
21) Which of these methods can be used to obtain a viable cell count?
a) counting chamber direct count
b) turbidity measurement
c) plate counts of serial dilutions
d) loop dilution
e) optical density
23) The plate count method was used to estimate the number of bacteria in a culture over time.
Serial dilutions were made of culture samples at various time points. A 0.1 ml portion of the 10-6
dilution was spread over the surface of a nutrient agar plate for each time point. The plates were
incubated for 24 hrs and the colony forming units (CFU) were counted on each plate. A total of
45 colonies were counted on the plate for the 30 minute time point. What was the cell population
for this time point?
a) 45 X 104 CFU/ml
b) 45 X 105 CFU/ml
c) 45 X 106 CFU/ml
d) 45 X 107 CFU/ml
e) 45 X 108 CFU/ml
24) Fresh media is inoculated with an actively growing Escherichia coli culture. You measure
the optical density (OD) at the time of inoculation and record a value of 0.05) Two hours later
you take another reading and record a optical density of 0.2) What is the generation time for your
culture?
a) 30 minutes
b) 40 minutes
c) 50 minutes
d) 60 minutes
e) Cannot determine from the information given.
25) If a cell culture contains 400 cells/ml at time = 0 and it has a generation time of 30 minutes,
how many cells (cells/ml) will be present after 2 hours of incubation?
a) 1200 cells/ml
b) 1600 cells/ml
c) 2400 cells/ml
d) 3200 cells/ml
e) 6400 cells/ml
27) How long would it take a culture of E. coli with a starting cell density of 1 X 105 cells/ ml to
reach a cell density of 1 X 108 cells/ml if it had a generation time of 30 minutes?
a) 3 hours
b) 4 hours
c) 5 hours
d) 6 hours
e) 7 hours
36) Many pharmaceutical products are heat sensitive so they are sterilized:
a) by ultraviolet radiation.
b) by ionizing radiation.
c) with ozone gas.
d) with chlorine gas.
e) by freezing.
50) The growth curve generated for a microbial batch culture consists of four phases. Explain
what is happening to the culture during each of the phases.