Micro Lab final exam

1. Define niche
A. ecological environment
B. by-product of microbial metabolic activities
C. microbial growth
D. host-parasite relationship
E. None of the above

ecological environment

2. Microbes may attempt to adjust the environment (temperature, pH, etc.) to their optimal requirements in order to compete for nutrients.
A. True
B. False

true

3. The pathogenesis of disease can involve digestion of tissues by extracellular enzymes or physical blocking of capillaries due to unlimited microbial growth.
A. True
B. False

true

4. The study of microbial metabolism is essential to a complete understanding of the host-parasite relationship.
A. True
B. False

true

5. Microorganisms, as other forms of life, may alter their environment to a certain extent and use chemical compounds in solutions as sources of energy or components for growth and reproduction.
A. True
B. False

true

6. All cellular activities are mediated by:
A. Enzymes
B. Carbohydrates
C. Lipids
D. All of the above
E. None of the above

enzymes

7. In order to observe microbial enzymatic activity, various kinds of specifically prepared media are inoculated with pure cultures of microorganisms.
A. True
B. False

true

8. Microbes multiply during the refrigeration period and exhibit their respective enzymatic activities.
A. True
B. False

false

9. Many distinctive enzyme activities can be demonstrated by testing for the by-products resulting from the action of enzymes on specific substances within the special media.
A. True
B. False

true

10. Microbial species can differ greatly and may be identified by the actions of their enzymes.
A. True
B. False

true

11. By using a series of different media or biochemical tests, a pattern of activity can be established for a species. Such reaction patterns can be used in the identification and the differentiation of microorganisms.
A. True
B. False

true

12. Microbial reaction patterns to the following media can be used in the identification and the differentiation of microorganisms.
A. Starch agar
B. Nutrient gelatin
C. Urea broth
D. Hydrogen peroxide
E. All of the above

all of the above

13. Gram stains alone can be used to identify microorganisms.
A. True
B. False

false

14. ________are the prime source of energy and carbon for the synthesis of cellular components.
A. Enzymes
B. Carbohydrates
C. Lipids
D. Simple sugars
E. None of the above

carbohydrates

15. _______ such as glucose and galactose are important in both human and microbial metabolism.
A. Enzymes
B. Carbohydrates
C. Lipids
D. Simple sugars
E. None of the above

simple sugars

16. In the case of microorganisms, most of the carbohydrates available to them are ________ that are made up of many ________ units.
A. Polysaccharide, monosaccharide
B. Monoaccharide, monosacccharide
C. Monosaccharide, polysacccharide
D. Disaccharide, trisacccharide
E. None of the above

polysaccharide, monosaccharide

17. Cellulose and starch are two common examples of polysaccharides that are made up of many monosacccharide units.
A. True
B. False

true

18. Cellulose and starch are polymers of glucose.
A. True
B. False

true

19. The basic difference between cellulose and starch is the structural arrangement of the glucose units, which leads to the chemical difference.
A. True
B. False

true

20. The enzyme responsible for the hydrolysis of starch is called amylase.
A. True
B. False

true

21. Amylase is an extracellular enzyme
A. True
B. False

true

22. Amylase is secreted through the cell membrane to degrade complex substances (starch) into smaller units (maltose), which can readily enter the cell.
A. True
B. False

true

23. Amylase acts on starch to yield maltose (a disaccharide composed of two glucose molecules), which is then further digested by cells.
A. True
B. False

true

24. To inoculate a starch agar plate for the amylase test place a
straight line of inoculum from a pure bacterial culture down the center of your starch plate.
A. True
B. False

true

25. To inoculate a starch agar plate for the amylase test perform the streak plate technique of inoculation.
A. True
B. False

false

26. After 24-48 hours of incubation at 37°C the amylase results can immediately be determined visually.
A. True
B. False

false

27. You must carefully flood the starch agar plate with gram’s iodine solution to analyze the amylase test results.
A. True
B. False

true

28. A positive reaction to the amylase test will be a zone of inhibition around the microbial growth
A. True
B. False

false

29. A clear zone around the microbial growth is an indication that starch has been hydrolyzed by bacterial amylase.
A. True
B. False

true

30. Iodine will stain starch a _____color.
A. Blue
B. Bluish-purple
C. Purple
D. Red
E. None of the above

bluish-purple

31. Where amylase has digested the starch, there will be a colorless zone indicating that the starch was hydrolyzed.
A. True
B. False

true

32. In a ______amylase test reaction, the whole plate, including the area around the organism, remains a bluish-purple color, indicating that the organism did not have the enzyme amylase.
A. Negative
B. False-negative
C. Positive
D. False-Positive
E. A and B

A and B

33. Protein hydrolysis can be detected using a gelatin slant agar tube
A. True
B. False

false

34. When in solution, gelatin agar liquefies at warm temperatures of about 15°C.
A. True
B. False

false

35. At room temperature or below, gelatin agar becomes liquid.
A. True
B. False

false

36. When bacteria that produce the enzyme gelatinase are grown in a gelatin medium, the enzyme hydrolyzes the gelatin molecule and the medium cannot solidify, even at cold temperature.
A. True
B. False

true

37. Gelatinase is a:
A. Protease
B. DNAse
C. Endonuclease
D. All of the above
E. None of the above

protease

38. Inoculate the gelatin deep with a pure culture, using a stab with an inoculation needle and incubate at:
A. 4°C for 48 hours
B. 25°C for 48 hours
C. 30°C for 48 hours
D. 37°C for 48 hours
E. None of the above

25 C for 48 hours

39. A gelatin deep agar tube will be liquid at:
A. 4°C for 48 hours
B. 25°C for 48 hours
C. 37°C for 48 hours
D. All of the above
E. None of the above

37 C for 48 hours

40. To ensure gelatin hydrolysis after incubation for 24-48 hours, place tubes at 4°C for 30 min. and examine the tubes for:
A. Liquefaction
B. Polymerization
C. Putrefaction
D. Color change
E. pH change

liquefaction

41. To ensure gelatin hydrolysis after incubation for 24-48 hours, place tubes at 4°C for 30 min. and if all tubes are solidified, replace them in the incubator for further growth and re-examine them every:
A. 6 hours for 2 days
B. 12 hours for 3 days
C. 24 hours for 3 days
D. 24 hours for 2 days
E. All of the above

24 hours for 3 days

42. A positive gelatinase result is indicated by liquefied agar in a tube that remains liquid even after being placed in the refrigerator.
A. True
B. False

true

43. _____ is an intestinal microbe with the ability to produce urease.
A. Proteus
B. M. luteus
C. S. marscesans
D. C. albicans
E. S. cerevesiae

proteus

44. The urease enzyme splits ____ from the ____ molecule
A. Ammonia, water
B. Ammonia, oxygen
C. Ammonia, carbon
D. Ammonia, urea
E. All of the above

ammonia, urea

45. Most enteric pathogens do not produce urease.
A. True
B. False

true

46. ____is a common cause of urinary tract infections.
A. Proteus
B. Escherichia coli
C. Clostridium difficile
D. A and B
E. B and C

A and B

47. Urea broth is a buffered solution of ____extract and urea.
A. Soy
B. Blood
C. Yeast
D. Carageenan
E. C and D

Carageenan

48. Urea broth contains phenol red as a ___indicator.
A. Temperature
B. pH
C. Nutrients
D. Isoelectric point
E. None of the above

pH

49. Since urea is unstable and breaks down in the autoclave steam pressure, the media is sterilized by ____
A. Heat
B. Formalin
C. Filtration
D. Glutaraldehyde
E. None of the above

Glutaraldehyde

50. When urease is produced by an organism in urea broth, the ammonium that is released
A. raises the pH
B. decreases the pH
C. maintains the pH
D. neutralizes the pH
E. None of the above

raisesthe pH

51. When the pH increases, ______changes from a yellow-orange color (pH 6.8) to a pink color (pH 8.1 or more).
A. trypan blue
B. trypsin
C. phenol red
D. phenol orange
E. phenol yellow

phenol red

52. If urea broth turns a hot pink color within ____ hours post inoculation, this indicates the presence of the enzyme urease.
A. 72
B. 24
C. 4
D. 8
E. 48

48

53. Catalase is a/an¬¬¬_____ that catalyzes the breakdown of hydrogen peroxide (H2O2) to water and oxygen.
A. extracellular enzyme
B. endotoxin
C. secreted enzyme
D. intracellular enzyme
E. None of the above

intracellular enzyme

54. The catalase test is useful for a quick separation of catalase-positive Staphylococci from catalase-negative Streptococci and Enterococci.
A. True
B. False

true

55. The presence of _____can be detected by adding a drop of 5% H2O2 to a colony and observing for the production of bubbles of O2. This test can also be performed in a drop of H2O2 on a slide.
A. Casease
B. Amylase
C. Collagenase
D. Catalase
E. Superoxide dismutase

catalase

56. Blood cells contain catalase.
A. True
B. False

true

57. Coagulase is an enzyme, produced by____, which coagulates blood plasma. Coagulase helps the organism evade the host immune system by isolating itself from antibodies or cells that might attempt to phagocytize the bacteria.
A. Micrococcus luteus
B. S. pneumoniae
C. S. epidermidis
D. S. aureus
E. None of the above

S aureus

58. Coagulase is not produced by S. epidermidis or by any other gram-positive coccus.
A. True
B. False

true

59. The coagulase test is done in _____and the sample is incubated at 37°C for 24 hours. A tube that solidifies (clots) shows the presence of coagulase. This reaction can occur as fast as 4 hours.
A. sheep plasma
B. rabbit plasma
C. mouse plasma
D. human plasma
E. None of the above

rabbit plasma

60. How does the starch agar test demonstrate that amylase is an exoenzyme?
A. Starch in the agar is hydrolyzed in the presence of amylase
B. Starch in the microbe is hydrolyzed in the presence of amylase
C. Lipids in the agar are hydrolyzed in the presence of amylase
D. Casein in the agar is hydrolyzed in the presence of amylase
E. None of the above

starch in the agar is hydrolyzed in the presence of amylase

61. What is the benefit to a microbe in producing a protease such as gelatinase?
A. Hydrolyze protein
B. Hydrolyze lipid
C. Hydrolyze starch
D. Enable microbial penetration deeper into the body
E. A and D

A and D

62. Why is the breakdown of peroxide useful to a bacterium?
A. Neutralize toxins
B. Neutralize free radicals
C. Neutralize reactive oxygen species
D. Peroxide is used in microbial metabolism
E. B and C

B and C

63. Bacterial identification is based on:
A. Morphology
B. Arrangement
C. Staining characteristics
D. Biochemical differences and genetic analysis
E. All of the above

all of the above

64. Indole production from tryptophan differentiates _____ from other gastrointestinal bacteria.
A. Proteus
B. Escherichia coli
C. Clostridium difficile
D. A and B
E. B and C

Escherichia coli

65. If a red color is produced after incubation in SIM medium and after the addition of Erhlich’s reagent, the bacterium hydrolyzes _____to indole.
A. H2S
B. Valine
C. Phenylalanine
D. Threonine
E. Tryptophan

tryptophan

66. What does Erhlich’s reagent do?
A. Detects motility
B. Detects H2S
C. Detects tryptophan
D. Detects indole

detects indole

67. H2S production in SIM medium from sulfur containing amino acids differentiates Proteus vulgaris, Shigella and Salmonella from other gastrointestinal bacteria.
A. True
B. False

true

68. The black color produced when sulfur reacts with iron in the SIM medium indicates _______
A. Motility
B. H2S production
C. Tryptophan production
D. Indole production
E. None of the above

H2S production

69. Define carbohydrate fermentation
A. Production of acid from sugars
B. Production of acid and gas from sugars
C. Breakdown of sugars such as glucose and lactose
D. All of the above
E. None of the above

all of the above

70. Define coliforms:
A. rod-shaped
B. Gram-negative
C. non-spore forming
D. motile or non-motile
E. All of the above

All of the above

71. ______production is seen as the formation of bubbles in the inverted Durham fermentation tube, and ammonia production by a change in color from red to fuchsia.
A. H2O2
B. Gas
C. Nitrogen
D. Catalase
E. None of the above

gas

72. Escherichia coli produces alkaline by products and gas from lactose.
A. True
B. False

false

73. Motility assay: if SIM agar is inoculated properly, motile bacteria will move away from the line of inoculation and give a _____appearance.
A. Slimy
B. Undulating
C. Swimming
D. Fuzzy
E. Sharp

fuzzy

74. Many Gram-negative bacteria can be distinguished by the metabolic pathway they utilize to ferment fructose.
A. True
B. False

false

75. MR-VP broth is used to test for the pathway used to ferment fructose.
A. True
B. False

false

76. MR-VP broth contains fructose as the only fermentable carbohydrate; peptone; and a phosphate buffer.
A. True
B. False

false

77. MR-VP broth is used to test for two glucose fermentation pathways: the “mixed acid” fermentation (detected by the Methyl Red Test) and the “butanediol” fermentation (detected by the Voges-Proskauer Test).
A. True
B. False

true

78. Some organisms, typified by E. coli, carry out a “mixed acid” fermentation, named for the large amounts of organic acids that are produced as end-products during the fermentation of glucose, gases may also be produced.
A. True
B. False

true

79. The large amount of ______that are produced during the fermentation of glucose overcome the buffering system in the MR-VP broth and lower the pH of the medium to about 4.0.
A. organic acids
B. mixed acids
C. butanediol
D. A and B
E. All of the above

A and B

80. The test uses methyl red, a pH indicator that has a red color at a pH lower than 4.5 and a yellow color when the pH is above 6.0.
A. 4.5, 6.0
B. 4.5, 5.0
C. 4.5, 7.0
D. 4.5, 8.0
E. None of the above

4.5, 6.0

81. A positive Methyl-Red test, which is indicative of the lowered pH of ________, will produce a light-red (pinkish) color when methyl red is added to the MR-VP broth (after incubation).
A. Ethanol production
B. carbon dioxide synthesis
C. formation of hydrogen gases
D. mixed acid fermentation
E. None of the above

mixed acid fermentation

82. The ethanol, carbon dioxide, and hydrogen gases that may also be formed during the Methyl-Red test are detected in the test.
A. True
B. False

false

83. Enterobacter forms ____ and ______, compounds that do not lower the pH of the medium.
A. Ethanol and 2,3 butanediol
B. 2,3 butanediol and acetylmethyl carbinol
C. 2,3 butanediol and (acetoin)
D. α-naphthol and KOH
E. None of the above

Ethanol and 2,3 butanediol

84. Although there is no test to detect _____, the presence of its precursor, _______can be detected by the Voges-Proskauer test.
A. 2,3 butanediol, acetylmethyl carbinol
B. 2,3 butanediol, (acetoin)
C. α-naphthol, KOH
D. A and B
E. None of the above

A and B

85. In the Voges-Proskauer test, ___________are added to the MR-VP broth. The components of the __________, react with the acetoin to yield products that produce a brick-red color.
A. Barritt’s Reagents
B. α-naphthol and KOH
C. 2,3 butanediol, (acetoin)
D. α-naphthol, KOH
E. A and B

A and B

86. The formation of gases is detected in the Voges-Proskauer test.
A. True
B. False

false

87. During the MR-VP test, an inoculated tube should be broth incubated at 37°C for _____.
A. 1 to 5 days
B. 2 to 5 days
C. 3 to 5 days
D. 4 to 5 days
E. None of the above

2 to 5 days

88. Barritt’s A reagent is α-naphthol and Barritt’s B reagent is KOH
A. True
B. False

true

89. All bacteria can utilize citrate as their sole carbon and energy source.
A. True
B. False

false

90. Simmon’s citrate is used to determine a nitrogen and energy source for microbial metabolism.
A. True
B. False

false

91. Simmon’s citrate contains sodium potassium as the only source of carbon.
A. True
B. False

false

92. Ammonia present in Simmon’s citrate supplies the nitrogen source
A. True
B. False

false

93. Addition of nitrogen to Simmon’s citrate would supply another carbon source besides citrate.
A. True
B. False

false

94. Simmon’s citrate contains trypan blue, a pH indicator that is green at neutral pH but turns blue under alkaline conditions (pH greater than 7.6).
A. True
B. False

false

95. Since citrate utilization occurs under______, a slanted medium is used to maximize the surface area and contact with oxygen.
A. anaerobic conditions
B. microaerophile conditions
C. aerobic conditions
D. none of the above
E. all of the above

aerobic conditions

96. The _____ in Simmon’s citrate medium is transported into the bacterial cell by citrate permease and then hydrolyzed by citrase to form an acid and a gas.
A. citrate
B. pyruvic acid
C. carbon dioxide
D. none of the above
E. all of the above

citrate

97. The _____produced during the Simmon’s citrate test diffuses out of the cell and reacts with Sodium ion and water in the medium to form compounds such as sodium carbonate, which raise the pH of the medium.
A. citrate
B. pyruvic acid
C. carbon dioxide
D. none of the above
E. all of the above

carbon dioxide

98. The alkaline conditions of a positive Simmon’s citrate test causes the bromothymol blue to change the medium color from green to blue.
A. True
B. False

true

99. The inoculated Simmon’s citrate tube should be incubated at 37° C for _____
A. 2 to 5 days
B. 1 to 2 days
C. 72 hours
D. 4 to 5 days
E. None of the above

1 to 2 days

100. In the absence of a color change, evidence of growth on the slant is indicative of a positive Simmon’s citrate test
A. True
B. False

true