Microbiology chapter 4

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1

1. All the bacterial cells that result from the replication of a single original bacterial organism are said to be a
A. population.
B. pure culture.
C. lag culture.
D. mutant culture.

B. pure culture.

2

2. The scientist that contributed most to the development of pure culture techniques was
A. Alexander Fleming.
B. Louis Pasteur.
C. Edward Jenner.
D. Robert Koch.

D. Robert Koch.

3

3. The solidifying agent used most successfully in bacterial nutrient media is
A. gelatin.
B. peptone.
C. agar.
D. starch.

C. agar.

4

4. Prokaryotic cells divide by a process known as
A. conjugation.
B. mitosis.
C. binary fusion.
D. binary fission.

D. binary fission.

5

5. In nature, bacteria
A. often grow in close association with many other kinds of organisms.
B. may remain in a prolonged exponential phase.
C. frequently synthesize structures such as slime layers.
D. may adhere to surfaces by means of pili and slime layers.
E. All of the choices are correct.

E. All of the choices are correct.

6

6. Biofilms
A. are a haphazard mixture of bacteria.
B. are a polysaccharide-encased community of microorganisms.
C. may enhance bioremediation efforts.
D. may protect organisms against harmful chemicals.
E. are a polysaccharide-encased community of microorganisms, may enhance bioremediation efforts, AND may protect organisms against harmful chemicals.

E. are a polysaccharide-encased community of microorganisms, may enhance bioremediation efforts, AND may protect organisms against harmful chemicals.

7

7. The simplest technique for isolating bacteria in growth media is referred to as the
A. pour-plate method.

B. streak-plate method.

C. serial dilution method.
D. MPN method.

B. streak-plate method.

8

8. Bacteria may be stored
A. on a slant in the refrigerator.
B. frozen in glycerol solution.
C.

freeze-dried.

D. in broth at 37C.
E.

on a slant in the refrigerator, frozen in glycerol solution, AND freeze-dried.

E.

on a slant in the refrigerator, frozen in glycerol solution, AND freeze-dried.

9

9. In the growth curve of a bacteria population, the bacteria are rapidly increasing in number in the
A. lag phase.
B. exponential (log) phase.
C. stationary phase.
D. decline phase.
E. boomer phase.

B. exponential (log) phase.

10

10. During which phase of growth are bacteria most susceptible to antibiotics?
A.

Lag

B.

Stationary

C.

Exponential (log)

D.

Decline

C.

Exponential (log)

11

When doing experiments with bacteria,

A. it is usually not necessary to standardize which stage of growth is used.
B. it is best to use colonies as all the bacteria in a colony are at the same stage of growth.
C. it is best to use bacteria from the same stage of growth.
D. the age of the bacteria is not important.

C. it is best to use bacteria from the same stage of growth.

12

12. During which phase of the bacterial growth curve does the total number of viable cells decline?
A.

Stationary

B.

Lag

C.

Exponential

D.

Death

D.

Death

13

13. The lag phase of the bacterial growth curve is marked by
A. a decrease in cell mass.
B. dormant, metabolically inactive cells.
C. metabolically active cells.
D. vigorously dividing cells.

C. metabolically active cells.

14

14. Late log phase of the bacterial growth curve
A. is marked by the production of primary metabolites.
B. is marked by the production of secondary metabolites.
C. is a transition into the death phase.
D. shows a decline in cell numbers.

B. is marked by the production of secondary metabolites.

15

15. During which phase of the bacterial growth curve does a bacterial population become much more resistant to harmful conditions?
A.

Lag phase

B.

Exponential phase

C.

Stationary phase

D.

Late log phase

D.

Late log phase

16

16. A urine sample with more than 100,000 organisms is considered indicative of infection. A urine sample containing 5,000 bacteria,with a generation time of 30 minutes, sits for 3 hours before finally being assayed. How many bacteria will then be present within the sample?
A. 10,000
B. 64,000
C. 100,000
D. 320,000

D. 320,000

17

17. A pure culture in exponential growth phase has a bacterial concentration of 6.4 x 108 cells/ml. If the bacterium has a generation time of 1 h, how long ago was the cell concentration 8.0 x 107 cells/ml?
A. 1 h
B. 2 h
C. 3 h
D. 4 h

C. 3 h

18

18. In a rapidly multiplying bacterial population, cell numbers increase
A. arithmetically.
B. logarithmically.
C. linearly.
D. indirectly.

B. logarithmically.

19

19. Generally the proteins of thermophiles
A. resist denaturation.
B. react more efficiently with DNA.
C. are easily denatured.
D. have a particular amino acid sequence that restricts bond formation.
E. are easily denatured AND have a particular amino acid sequence that restricts bond formation.

A. resist denaturation.

20

20.

A hot tub (approx. 104F or 40C) would most likely contain

A. psychrophiles.
B. partiers.
C. thermophiles.
D. mesophiles.

D. mesophiles.

21

21. The optimal temperature for most human pathogens might be expected to range from
A. 35-40C.
B. 20-45C.
C. 15-25C.
D. 93-98.6C.

A. 35-40C.

22

22. Bacteria on fish caught in the Arctic Ocean would
A. be psychrophiles.
B. be mesophiles.
C. continue to grow while the fish is in the refrigerator.
D. not grow very well in the refrigerator.
E. be psychrophiles AND continue to grow while the fish is in the refrigerator.

E. be psychrophiles AND continue to grow while the fish is in the refrigerator.

23

23.

Mycobacterium leprae is typically found infecting the ears, toes, and fingers of its host due to its

A. requirement for well-oxygenated blood.
B. easy access to those parts.
C. need for cooler temperatures.
D. long incubation period.

C. need for cooler temperatures.

24

24. Organisms that require gaseous oxygen for metabolism are referred to as
A. facultative aerobes.
B. obligate aerobes.
C. facultative anaerobes.
D. microaerophiles.

B. obligate aerobes.

25

25. Which of the following is/are obligate aerobes?
A. Clostridium botulinum
B. Escherichia coli
C. Micrococcus luteus
D. Helicobacter pylori

C. Micrococcus luteus

26

26. Organisms that are indifferent to the presence of oxygen and do not use it are
A. aerotolerant anaerobes.
B. facultative anaerobes.
C. obligate aerobes.
D. microaerophiles.

A. aerotolerant anaerobes.

27

27. The enzymes that deal with toxic oxygen-containing molecules is/are
A. glycolase.
B. superoxide dismutase.
C. catalase.
D.

cytochrome oxidase.

E. superoxide dismutase AND catalase.

E. superoxide dismutase AND catalase.

28

28. Shake tubes are used to determine the
A. pH requirements for bacterial growth.
B. temperature requirements for bacterial growth.
C. oxygen requirements for bacterial growth.
D. salt requirements for bacterial growth.

C. oxygen requirements for bacterial growth.

29

29. The optimum pH for growth of most species of bacteria is
A. pH 5.
B. pH 7.
C. pH 9.
D. pH 6.

B. pH 7.

30

30. High concentrations of salt and sugar in foods
A. are useful in preserving the food.
B. tend to draw water out of a cell.
C. tend to force water into a cell, causing plasmolysis.
D. have no effect on water availability.
E. are useful in preserving the food AND tend to draw water out of a cell.

E. are useful in preserving the food AND tend to draw water out of a cell.

31

31. Carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur may be considered
A. minor elements.
B. major elements.
C. neutral elements.
D. acidic elements.

B. major elements.

32

32. Trace elements
A.

include zinc, copper, and manganese.

B. are required in large amounts.
C. may be needed for enzyme function.
D. are involved in maintaining pH in the cell.
E.

include zinc, copper, and manganese AND may be needed for enzyme function.

E.

include zinc, copper, and manganese AND may be needed for enzyme function.

33

33. Small organic molecules that must be provided to bacteria in order for them to grow are called
A. minerals.
B. growth factors.
C. water.
D. vitamins.

B. growth factors.

34

34. The prefix photo- indicates that an organism will make use of _______ for energy purposes.
A. chemicals
B. organics
C. light
D. inorganics

C. light

35

35. Organisms that use organic molecules as their source of carbon are called
A. chemotrophs.
B. organoheterotrophs.
C. heterotrophs.
D. autotrophs.

C. heterotrophs.

36

36. Organisms may derive energy from
A. sunlight.
B. metabolizing chemical compounds.
C. little tiny AAAAAAAAA batteries.
D. temperature gradients.
E. sunlight AND metabolizing chemical compounds.

E. sunlight AND metabolizing chemical compounds.

37

37. Organisms that use CO2 as their source of carbon are called
A. organotrophs.
B. heterotrophs.
C. autotrophs.
D. chemotrophs.

C. autotrophs.

38

38. Chemoheterotrophs
A. use sunlight as an energy source.
B.

use preformed organic molecules as a carbon source.

C.

use preformed organic molecules as an energy source.

D. use inorganic chemicals as an energy source.
E.

use preformed organic molecules as a carbon source AND as an energy source.

E.

use preformed organic molecules as a carbon source AND as an energy source.

39

39. An organism called Bacillus fastidiosus
A. might be expected to be very flexible as to growth requirements.
B. might be expected to be very strict as to its growth requirements.
C.

would probably be grown on amedium rich in growth factors.

D.

might be expected to have a rod shape.

E.

might be expected to be very strict as to its growth requirements, would probably be grown on amedium rich in growth factors, AND might be expected to have a rod shape.

E.

might be expected to be very strict as to its growth requirements, would probably be grown on amedium rich in growth factors, AND might be expected to have a rod shape.

40

40. Peptone
A. refers to a hydrolysate of carbohydrates used in growth media.
B. refers to a hydrolysate of proteins used in growth media.
C. consists of a water extract of beef.
D. consists of a mix of monosaccharides and oligosaccharides.
E. refers to a hydrolysate of proteins used in growth media AND consists of a water extract of beef.

B. refers to a hydrolysate of proteins used in growth media.

41

41. Medically important bacteria are often
A. grown on agar containing blood.
B. grown at 37C.
C. grown on agar containing chocolate.
D. grown at a pH of 5.
E. grown on agar containing blood AND grown at 37C.

E. grown on agar containing blood AND grown at 37C.

42

Products that limit pH changes are often incorporated into media and are referred to as

A. enzymes.
B. bases.
C. buffers.
D. acids.

C. buffers.

43

43. A medium that inhibits the growth of organisms other than the one being sought is termed a(n)
A. synthetic medium.
B. specific culture medium.
C. selective medium.
D. enrichment medium.

C. selective medium.

44

44. MacConkey agar is
A. a selective agar.
B. a differential agar.
C. a selective and differential agar.
D. used to distinguish between bacteria by the type of hemolysis observed.

C. a selective and differential agar.

45

45. Candle jars are usually used to
A. store candles.
B. provide an atmosphere with CO2.
C. stimulate the growth of obligate anaerobes.
D. prevent the growth of obligate aerobes.
E. provide an atmosphere with CO2 AND stimulate the growth of obligate anaerobes.

B. provide an atmosphere with CO2.

46

46. In the cultivation of microaerophilic and anaerobic bacteria,
A. a(n) candle/anaerobe jar is sufficient.
B. atmospheric oxygen in a(n) candle/anaerobe jar is converted to water.
C.

a packet containing chemicals that generate carbon dioxide and hydrogen is used in a(n) candle/anaerobic jar.

D. oxidizing agents are incorporated into the media that react with oxygen.

B. atmospheric oxygen in a(n) candle/anaerobe jar is converted to water.

47

47. Agar
A. is a useful nutrient source for most bacteria.
B. is a hydrolysate of proteins.
C. stays liquid through the typical range of incubation temperatures.
D. has chemical and physical properties that make it almost ideal for solidifying media.

D. has chemical and physical properties that make it almost ideal for solidifying media.

48

48. Agar replaced gelatin as the gelling (solidifying) agent for media because
A. agar is much cheaper.
B. much fewer bacteria can break down agar than gelatin.
C. agar is solid at body temperature.
D. gelatin became unavailable during World War II.
E. much fewer bacteria can break down agar than gelatin AND agar is solid at body temperature.

E. much fewer bacteria can break down agar than gelatin AND agar is solid at body temperature.

49

58. A microbe is discovered growing near a deep sea thermal vent. When researchers bring a sample up to the surface and try to grow it in a lab at room temperature in a normal incubator, they are unsuccessful. Why?
A.

The pressure isn't the same at sea level as it is on the ocean floor.

B. Oxygen concentrations are very different between the two environments-it's possible the microbe is a strict anaerobe and is poisoned by the air (oxygen) in the lab.
C. Salt concentrations might be different in the media the researchers are attempting to use and the salt water the microbe is used to living in. This might be causing osmotic pressure differences that the microbe can't tolerate.
D.

The temperature is probably different-the thermal vent would be very hot, while these researchers are trying to grow this microbe at room temperature. The enzymes in the cells are probably outside of their normal operating range at room temperature, and therefore nonfunctional.

E. All of the above.

E. All of the above.

50

59. You are a microbiologist working for a pharmaceutical company and discover a new secreted metabolite that can serve as a medication. Your company asks you to oversee the production of the metabolite. Which of the following is something that is NOT important to consider if you need to grow 5,000 liter cultures of bacteria for the purpose of harvesting the metabolite they secrete?
A. The death rate of the bacteria after stationary phase is complete.
B. The ideal rate of input of new nutrients into the culture to maintain the cells in log phase.
C. The ideal rate of pulling off some of the culture in order to maintain the cells in log phase.
D. The best way to mix the large vat in order to keep it homogenous (constant throughout) in terms of nutrients, temperature, and oxygen levels.
E. The best way to keep the pH of the entire mixture at the ideal level to promote log phase growth.

A. The death rate of the bacteria after stationary phase is complete.

51

60.

You are working in a clinical laboratory in a hospital setting. You're handed a throat swab from a patient. You are told specifically that the physician is only interested in the presence and type of Gram positive cells. Identification isn't the main goal here-just a first step to work towards determining what Gram positive cells might be there.What might you do first to go about working towards this goal?

A. Perform a Gram stain.
B. Streak the sample for isolation on a tryptic soy agar general purpose medium plate.
C. Streak the sample for isolation on a medium that is selective for Gram positive cells while suppressing Gram negative cell growth.
D. Grow the microbes on the swab by inoculating a tryptic soy broth liquid medium tube.
E. Perform an acid-fast stain.

A. Perform a Gram stain.

52

61. A physician sends a stool sample to your lab, and wants to know if there are lactose fermenting microbes in the sample. How might you determine if these microbes are present or not from this mixed-microbe specimen?
A. Streak the sample for isolation on Thayer-Martin agar (which contains lactose and particular antibiotics for selectivity).
B. Streak the sample for isolation on a blood agar plate (which contains lactose AND red blood cells that enrich the culture for iron).
C. Streak the sample for isolation on a MacConkey agar plate (which contains lactose and a pH indicator that turns pink when acid byproducts are present).
D. None of the above would work-there's no way to reliably determine this feature from the specimen given.

C. Streak the sample for isolation on a MacConkey agar plate (which contains lactose and a pH indicator that turns pink when acid byproducts are present).

53

62. You are in charge of water quality for your city's water treatment plant. Of the methods at your disposal, which will be the most efficient and cheapest method of determining the number of viable bacteria in the water coming out of your plant?
A. Direct counts using a microscope and a counting chamber.
B. Using a Coulter counter machine.
C. Performing serial dilutions of your samples and doing spread plate counts.
D. Using membrane filtration followed by placing the membrane in a growth medium for colony counts after incubation.
E. Biochemical analysis of secondary metabolites in the water that are given off by bacteria.

D. Using membrane filtration followed by placing the membrane in a growth medium for colony counts after incubation.

54

You take absorbance readings on a spectrophotometer across a 6-hour culture of E. coli cells growing in tryptic soy broth (TSB). Your absorbance readings clearly indicate a lag phase, a log phase, and a stationary phase. You come back in and take readings at 8, 10, 12, 14, and 16 hours, but the absorbance number remains the same. Shouldn't it start coming down as the closed batch culture enters death phase? What's the most likely thing that is happening?

A. Clearly, something is wrong with the spectrophotometer and it isn't measuring the correct values. Perhaps something is on the detector, making it register falsely high absorbance numbers.
B. When we establish a growth curve, we should actually plot the log of the number of viable cells vs. time. However, a spectrophotometer can only measure absorbance. Absorbance is NOT the same as the number of viable cells. Many of the cells in the tube are most likely dead, but the machine can't discriminate between a live cell and a dead one. This keeps the absorbance high even into the death phase.
C. It'll happen-E. coli just grow slowly. We haven't gotten to the end of the stationary phase yet. Be patient!
D. Perhaps there's a big smudge of something on the tube that is blocking some of the light. This would lead to an elevated reading for every timepoint after the smudge was placed on the tube.

B. When we establish a growth curve, we should actually plot the log of the number of viable cells vs. time. However, a spectrophotometer can only measure absorbance. Absorbance is NOT the same as the number of viable cells. Many of the cells in the tube are most likely dead, but the machine can't discriminate between a live cell and a dead one. This keeps the absorbance high even into the death phase.


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