Micro Chapter 6

1) A(n) ________ organism require(s) oxygen for growth. 1)
A) anaerobic
B) obligate aerobic
C) facultative anaerobic
D) aerotolerant and an anaerobic
E) aerotolerant

B) obligate aerobic

2) A microbe that grows only at the bottom of a tube of thioglycollate medium is probably a(n) 2)
A) obligate aerobe.
B) obligate anaerobe.
C) facultative anaerobe.
D) aerotolerant anaerobe.
E) microaerophile.

B) obligate anaerobe.

3) Blood agar plates are an example of ________ medium. 3)
A) selective
B) defined
C) differential
D) transport
E) reducing

C) differential

4) Which of the following quantification techniques can distinguish living cells from dead cells in a
culture?
4)
A) turbidity
B) microscopic counts
C) a Coulter counter
D) metabolic activity
E) dry weight

D) metabolic activity

5) Joan wants to discover a microbe capable of degrading an environmental contaminant. Which of
the following is the process she should use?
5)
A) enrichment culture
B) cell culture
C) chemostat
D) nitrogen fixation
E) quorum sensing

A) enrichment culture

6) All of the following are used to protect organisms from the toxic by-products of oxygen EXCEPT 6)
A) carotenoids.
B) catalase.
C) peroxidase.
D) protease.
E) superoxide dismutase.

D) protease.

7) When cells are metabolically active but not dividing, they are in the ________ phase. 7)
A) lag
B) exponential
C) log
D) death
E) stationary

A) lag

8) Which of the following is an indirect method for estimating the number of microbes in a sample? 8)
A) MPN
B) membrane filtration
C) viable plate counts
D) Coulter counter
E) turbidity

E) turbidity

9) The ________ method provides an estimate of the CFUs (colony-forming units) in a sample 9)
A) viable plate-count
B) streak-plate
C) turbidity
D) direct microscopic-count
E) Coulter-counter

A) viable plate-count

10) A microbe recovered from an environmental sample grows on a medium composed of agar and a
mix of salts. The agar is not digested during incubation. The growth rate increases in high CO2
conditions. The organism is likely a(n)
10)
A) autotroph.
B) halophile.
C) heterotroph.
D) chemotroph.
E) The answer cannot be determined from the information provided.

A) autotroph.

11) Which of the following organisms would be most likely to contaminate a jar of pickles? 11)
A) a thermophile
B) a mesophile
C) an acidophile
D) a neutrophile
E) an obligate anaerobe

C) an acidophile

12) During which growth phase are bacteria more susceptible to antimicrobial drugs? 12)
A) lag phase
B) stationary phase
C) log phase
D) death phase
E) The susceptibility is the same for all phases.

C) log phase

13) The use of salt and sugar in preserving various types of foods is an application of which of the
following concepts?
13)
A) hydrostatic pressure
B) osmotic pressure
C) quorum sensing
D) pH
E) nitrogen fixation

B) osmotic pressure

14) A microbiologist inoculates a growth medium with 100 bacterial cells/ml. If the generation time of
the species is 1 hour, and there is no lag phase, how long will it be before the culture contains more
than 10,000 cells/ml?
14)
A) 7 hours B) 2 hours C) 24 hours D) 3 hours E) 10 hours

A) 7 hours

15) A cell that uses an organic carbon source and obtains energy from light would be called a 15)
A) chemoheterotroph.
B) photoheterotroph.
C) chemoautotroph.
D) lithoautotroph.
E) photoautotroph.

B) photoheterotroph.

16) An aquatic microbe that can grow only near the surface of the water is probably which of the
following?
16)
A) a heterotroph
B) a chemotroph
C) an anaerobe
D) a phototroph
E) a lithotroph

D) a phototroph

17) An organism that produces catalase enzyme is protected from the harmful effects of 17)
A) singlet oxygen.
B) peroxide anion.
C) superoxide radical.
D) hydroxyl radical.
E) molecular oxygen.

B) peroxide anion.

18) An epidemiologist is investigating a new disease and observes what appear to be bacteria inside
tissue cells in clinical samples from victims. The scientist wants to try to isolate the bacteria in the
lab. What culture conditions are most likely to be successful?
18)
A) inoculation of a minimal medium broth
B) culturing on blood agar plates
C) inoculation of cell cultures
D) inoculation of EMB plates
E) incubation in an anaerobic culture system

C) inoculation of cell cultures

19) A means of reproduction in which duplicate DNA molecules are separated by cell elongation,
followed by formation of a septum to divide the cytoplasm is called
19)
A) mitosis.
B) budding.
C) logarithmic growth.
D) binary fission.
E) cell division.

D) binary fission.

20) A laboratory protocol lists the following ingredients: 1 g sucrose, 16.4 g Na2HPO4, 1.5 g
(NH4)3PO4, 0.02 g CaCO3, KNO3, water to 1 liter and autoclave. This recipe is for a ________
medium.
20)
A) complex broth
B) defined agar
C) reducing agar
D) complex enrichment broth
E) defined broth

E) defined broth

21) At temperatures higher than the maximum growth temperature for an organism, 21)
A) membranes become too fluid for proper function.
B) proteins are permanently denatured.
C) hydrogen bonds within molecules are broken.
D) hydrogen bonds are broken and proteins are permanently denatured.
E) hydrogen bonds are broken, proteins are denatured, and membranes become too fluid.

E) hydrogen bonds are broken, proteins are denatured, and membranes become too fluid

22) In the process of ________ microbes detect the presence and density of other microbes and modify
their metabolic activity in response.
22)
A) mutualism
B) quorum sensing
C) synergy
D) symbiosis
E) antagonism

B) quorum sensing

23) A 100 μl sample containing 1000 bacterial cells/μl in log phase growth is added to 9.9 ml of fresh
culture medium broth. Assuming no nutrients are in limited supply, and a generation time of 30
minutes, how many bacteria will be present in the entire broth culture after six hours?
23)
A) 4.096 × 10^8
B) 6.0 × 10^5
C) 2.56 × 10^7
D) 6.0 × 10^6
E) 1.2 × 10^6

A) 4.096 × 10^8

24) Microbial growth rates are controlled in a chemostat by 24)
A) allowing waste products to accumulate.
B) maintaining a constant temperature.
C) promoting biofilm formation.
D) controlling the amount of available oxygen.
E) controlling the amount of a limiting nutrient.

E) controlling the amount of a limiting nutrient.

25) Microaerophiles are microbes that grow best at low 25)
A) hydrostatic pressure.
B) salt concentrations.
C) carbon dioxide levels.
D) oxygen levels.
E) pH values.

D) oxygen levels.

26) A clinical sample labeled as "sputum" was collected from 26)
A) the blood.
B) the lungs.
C) the skin.
D) the central nervous system.
E) a piece of tissue.

B) the lungs.

27) A microorganism found living under conditions of high ________ is a barophile. 27)
A) salt concentrations
B) hydrostatic pressure
C) oxygen concentrations
D) pH values
E) carbon dioxide levels

B) hydrostatic pressure

28) Sodium thioglycollate is associated with which of the following types of media? 28)
A) selective media
B) transport media
C) complex media
D) reducing media
E) differential media

D) reducing media

29) Organisms that can grow with or without oxygen present are 29)
A) obligate aerobes.
B) facultative anaerobes.
C) either facultative anaerobes or aerotolerant anaerobes.
D) obligate anaerobes.
E) aerotolerant anaerobes.

C) either facultative anaerobes or aerotolerant anaerobes.

30) Metabolic activity is at maximum level in the ________ phase of growth. 30)
A) stationary
B) death
C) log
D) lag
E) intermediate

C) log

31) Obligate anaerobes may be cultured in the laboratory 31)
A) standard complex media.
B) on blood agar plates.
C) in a reducing medium.
D) in a standard incubator.
E) in standard Petri plates.

C) in a reducing medium.

32) Nitrogen is a growth-limiting nutrient for many organisms because 32)
A) it is required for synthesis of nucleotides.
B) it is required for lipid synthesis.
C) only a small number of bacteria are able to extract it from the atmosphere.
D) it is necessary for the biosynthesis of amino acids.
E) only a few microbes can extract it from the atmosphere, but all organisms require it for amino
acid and nucleotide synthesis.

E) only a few microbes can extract it from the atmosphere, but all organisms require it for amino acid and nucleotide synthesis.

33) The ________ of a population is the time it takes for the cells to double in number. 33)
A) generation time
B) exponential growth
C) log phase
D) binary fission
E) arithmetic growth

A) generation time

34) The method of obtaining isolated cultures that utilizes surface area to physically dilute specimens is
called
34)
A) transport media.
B) serial dilution.
C) enrichment culturing.
D) the pour-plate technique.
E) the streak-plate technique

E) the streak-plate technique

35) MacConkey agar plates represent ________ medium. 35)
A) a differential
B) a selective
C) a minimal
D) both a differential and a selective
E) both a minimal and a selective

D) both a differential and a selective

36) Creating conditions in the laboratory that promote the growth of some microbes while inhibiting
the growth of others is called
36)
A) reducing conditions.
B) differential culturing.
C) complex culturing.
D) selective enrichment culturing.
E) transport conditions.

D) selective enrichment culturing.

37) A device that removes wastes and adds fresh medium to bacterial cultures in order to prolong the
log phase of a culture is called a
37)
A) Coulter counter.
B) chemostat.
C) cytometer.
D) spectrophotometer.
E) pellicle.

B) chemostat

38) An organism that requires chemical nutrients which serve as final electron acceptors is a(n) 38)
A) chemotroph.
B) aerobe
C) phototroph.
D) lithotroph.
E) autotroph.

A) chemotroph

39) A capnophile is a microorganism that thrives in conditions of high
A) pH.
B) carbon dioxide levels.
C) hydrostatic pressure.
D) salt concentration.
E) oxygen levels.

B) carbon dioxide levels.

40) The generation time of bacterial cells is shortest during the ________ phase. 40)
A) longitudinal
B) lag
C) log
D) stationary
E) death

C) log

41) Human pathogens are classified as 41)
A) thermophiles.
B) thermoduric.
C) hyperthermophiles.
D) mesophiles.
E) psychrophiles.

D) mesophiles.

42) ________ are complex communities of various types of microbes that adhere to surfaces. 42)
A) Colonies
B) Isolates
C) Biofilms
D) Media
E) Aggregates

C) Biofilms

43) A Petroff-Hauser counting chamber is a(n) 43)
A) device that counts cells as they interrupt an electrical current.
B) apparatus that traps bacterial cells on a membrane filter where they can be counted.
C) device that measures the amount of light that passes through a culture.
D) device used to count numbers of bacterial colonies on a Petri plate.
E) glass slide containing an etched grid for counting microbes directly using a microscope.

E) glass slide containing an etched grid for counting microbes directly using a microscope.

44) A fastidious organism might be grown on which of the following types of media? 44)
A) enriched media
B) selective media
C) transport media
D) differential media
E) reducing media

A) enriched media

The correct sequence for the phases indicated by the letters A, B, C and D is
45)
A) lag phase, log phase, stationary phase, death phase.
B) stationary phase, lag phase, log phase, death phase.
C) log phase, stationary phase, lag phase, death phase.
D) death phase, stationary phase, log phase, lag phase.
E) death phase, log phase stationary phase, lag phase.

A) lag phase, log phase, stationary phase, death phase.

46) The conversion of nitrogen gas to ammonia is called nitrogen (metabolism/fixation).

fixation

47) A sample placed into fresh medium is initially in the (lag/log/stationary) phase of
microbial growth in most instances.

lag

48) A clinical sample of (urine/sputum/tissue) is called a biopsy.

tissue

49) Flow (spectrophotometry/cytometry) is a method of counting cells that have been stained
or tagged with fluorescent dyes.

cytometry

50) The preferred method for long term storage of bacteria is
(freezing/refrigeration/lyophilization).

lyophilization)

51) A gelling agent derived from algae that is useful for creating solid growth media is called
(broth/agar/starch).

agar

52) Alkalinophiles can survive in water up to pH (11.5/10/7.0).

11.5

53) A growth curve plots the (number/concentration) of viable organisms in a growing
population over time.

number

54) A(n) (culture/specimen/inoculum) is a sample of microorganisms introduced into a growth
medium.

inoculum

55) A pure culture is composed of cells that arise from a single (cell/inoculum/sample).

cell

56) The (peroxide/superoxide/hydroxyl) radical is formed during the incomplete reduction of
O2 during electron transport in aerobes.

superoxide

57) The (optimum/range/minimum) growth temperature is the temperature at which an
organism exhibits the highest growth rate.

optimum

58) Many photosynthetic organisms produce (catalase/carotenoids/dismutase) to protect
themselves from the damaging effects of singlet oxygen (1O2).

carotenoids

59) A (cytometer/spectrophotometer) can measure changes in the turbidity of a bacterial
culture.

spectrophotometer

61) Agar is a useful compound in the microbiology lab because it is an excellent nutrient for bacteria

False

62) Obligate anaerobes have enzymes such as superoxide dismutase to protect them from the
damaging effects of oxygen.

False

63) Nitrogen fixation is a process that occurs in all bacteria.

False

60) Organisms that require organic sources of carbon and energy are called
(chemoheterotrophs/chemoautotrophs/auxotrophs).

chemoheterotrophs

64) Thermoduric mesophiles are often responsible for spoilage of improperly canned foods

True

65) Quorum sensing is involved in the development and propagation of a biofilm

True

66) In spectrophotometry, 40% light transmission is the same thing as 60% absorbance of light.

true

67) A selective medium can be formulated either by including inhibitory chemical substances or by
leaving out a single crucial nutrient.

true

68) An obligate anaerobe can be cultured in a candle jar.

false

69) The only effective way to store bacterial cultures for short periods of time is to arrest their
metabolism by freezing.

false

70) Serial dilution can be used in combination with pour plates as a method for isolating pure cultures. 70)

True