1. The exponential growth rate of a bacterial culture is affected by all of the following except
A. the genetic potential of the organism.
B. the composition of the growth medium.
C. the number of cells initially inoculated into the culture vessel.
D. the condition of incubation.
2. The total number of viable microorganisms remains constant in stationary phase because
A. there is a balance between cell division and cell death.
B. there is a cessation of cell division even though the cells may remain metabolically active.
C. either there is a balance between cell division and cell death or there is a cessation of cell division even though the cells may remain metabolically active.
D. None of these answers are correct.
3. Cells may enter stationary phase because
A. depletion of an essential nutrient.
B. lack of available oxygen.
C. the accumulation of toxic waste products.
D. All of these.
4. Electronic counters are not generally useful for bacteria because
A. bacteria are too small to be detected.
B. small particles of debris interfere with accurate counts.
C. aggregation of bacteria into filaments interferes with accurate counts.
D. All of these.
5. A culture in a closed vessel to which no additional medium is added and from which no waste products are removed is called a __________ culture.
A. continuous
B. batch
C. fed-batch
D. semicontinuous
6. Microbial __________ is an increase in cell constituents that may or may not be accompanied by an increase in cell number.
7. The __________ is the length of time it takes for a population of microorganisms to double in number.
8. The number of generations per unit time (usually expressed as the number of generations per hour) is called the __________.
9. A culture system with constant environmental conditions maintained through continual provision of nutrient and removal of wastes is called __________ culture system.
A. continuous
B. batch
C. fed-batch
D. semicontinuous
10. An open system in which the growth rate is maintained by adding a nutrient (present in limiting quantities) at the same rate that medium containing microorganisms is removed is called
A. manostat.
B. chemostat.
C. turbidostat.
D. culturostat.
11. An open system in which the growth rate is maintained by the removal and addition of media at such a rate as to maintain a constant cell density is called a
A. manostat.
B. chemostat.
C. turbidostat.
D. culturostat.
12. In an open culture system, the rate at which media is added and removed is called the __________ rate.
A. dilution
B. chemostatic
C. pass-through
D. flow-through
13. Organisms that have a narrow range of growth temperatures are said to be
A. stenothermal.
B. minithermal.
C. eurythermal.
D. allothermal.
14. Organisms that have a wide range of growth temperatures are said to be
A. stenothermal.
B. minithermal.
C. eurythermal.
D. allothermal.
15. Which of the following is not considered a cardinal growth temperature?
A. the minimum temperature
B. the maximum temperature
C. the optimum temperature
D. All of these are considered cardinal growth temperatures.
16. Organisms that grow well at 0C and have optimum growth temperatures of 15C or lower are called
A. psychrotrophs.
B. psychrophiles.
C. frigiphiles.
D. mesophiles.
17. Organisms that grow well at 0C and have optimum growth temperatures between 20C and 30C are called
A. psychrotrophs.
B. psychrophiles.
C. frigiphiles.
D. mesophiles.
18. Organisms that do not require oxygen for growth but grow better in its presence are called
A. facultative anaerobes.
B. microaerophiles.
C. aerotolerant.
D. anoxygenic.
19. Organisms that ignore oxygen and grow equally well in its presence or absence are called
A. facultative anaerobes.
B. microaerophiles.
C. aerotolerant.
D. anoxygenic.
20. Organisms that are damaged by the normal atmospheric levels of oxygen (20%) but require oxygen at levels of 2-10% for growth are called
A. facultative anaerobes.
B. microaerophiles.
C. aerotolerant.
D. anoxygenic.
T F 21. One of the major advantages of a continuous culture system is that the cells can be maintained in the exponential growth phase for extended periods of time.
22. When a microorganism is placed in a(n) __________ solution, water will enter into the cell and cause it to burst unless something is done to prevent this.
A. hypotonic
B. isotonic
C. hypertonic
D. osmotonic
23. In order to remain fluid in cold temperatures, the membranes of psychrophiles have high levels of __________ fatty acids.
A. saturated
B. unsaturated
C. both saturated and unsaturated
D. neither saturated nor unsaturated
24. Organisms that are not affected by increased pressure are called
A. barotolerant.
B. osmotolerant.
C. barophilic.
D. osmophilic.
25. Organisms that require increased pressure for optimum growth are called
A. barotolerant.
B. osmotolerant.
C. barophilic.
D. osmophilic.
T F 26. In the process of photoreactivation, blue light is used to mediate the repair of thymine dimers produced in DNA by ultraviolet radiation.
T F 27. When a young, vigorously growing culture of bacteria is transferred to fresh medium of the same composition, the lag phase is usually short or absent.
T F 28. When a young, vigorously growing culture of bacteria is transferred to fresh medium of different composition, the lag phase is usually short or absent.
29. Most microorganisms maintain their internal pH
A. near neutral (pH 7).
B. near their optimum growth pH.
C. slightly acidic (pH 4-6).
D. slightly alkaline (pH 8-10).
30. Microorganisms are most nearly uniform in terms of chemical and physiological properties during __________ phase.
A. lag
B. log
C. stationary
D. decline
T F 31. Obligate anaerobes are usually poisoned by molecular oxygen but may grow in aerobic habitats if associated with facultative anaerobes that use up all available oxygen.
32. Which of the following is not a reason for the occurrence of a lag phase in a bacterial growth curve?
A. The cells may be old and depleted of ATP, essential cofactors, and ribosomes that must be synthesized before growth can begin.
B. The medium may be different from the previous growth medium so that the cells must synthesize new enzymes to utilize different nutrients.
C. The organisms may have been injured and require time to recover.
D. All of these are potential reasons.
33. Organisms that can grow in habitats with low water availability (high osmotic pressure) by maintaining a high internal salt concentration are called __________ organisms.
34. Organisms that require high levels of sodium chloride in order to grow are called __________ organisms.
35. Organisms that have their optimum growth pH between 1.0 and 5.5 are called __________.
36. Organisms that have their optimum growth pH between 5.5 and 8.5 are called __________.
37. Organisms that have their optimum growth pH between 8.5 and 11.5 are called __________.
T F 38. During the death (decline) phase, organisms are dying at an exponential rate.
39. Which of the following cannot be used to estimate the number of microorganisms in a culture?
A. direct counts of microbial cells
B. counts of viable cells using colony growth procedures
C. measurements of microbial biomass
D. All of these can be used to estimate the number of microorganisms in a culture.
40. If all cell components are synthesized at constant rates relative to one another, the culture is said to be in __________ growth; however, if the rates of synthesis of some components change relative to the rates of synthesis of other components, the culture is said to be in __________ growth.
41. At 4:00 p.m. a closed flask is inoculated with 10,000 cells. The lag phase lasts 1 hour. At 9:00 p.m. the culture enters stationary phase with a population of 65 million cells. The number of generations that have occurred is
A. 15.
B. 16.
C. 17.
D. 18.
42. At 4:00 p.m. a closed flask is inoculated with 10,000 cells. The lag phase lasts 1 hour. At 9:00 p.m. the culture enters stationary phase with a population of 65 million cells. The mean generation time is
A. 15 minutes.
B. 20 minutes.
C. 25 minutes.
D. 30 minutes.
43. At 4:00 p.m. a closed flask is inoculated with 10,000 cells. The lag phase lasts 1 hour. At 9:00 p.m. the culture enters stationary phase with a population of 65 million cells. At what time is the population half maximal?
A. 6:30 p.m.
B. 7:00 p.m.
C. 8:30 p.m.
D. 8:45 p.m.
44. Organisms that grow near deep-sea volcanic vents are likely to be
A. psychrophilic.
B. psychrotrophic.
C. mesophilic.
D. thermophilic.
45. Organisms that grow near deep-sea volcanic vents are likely to be
A. barophilic.
B. barotolerant.
C. either barophilic or barotolerant.
D. neither barophilic nor barotolerant.
46. Organisms that grow below the surface of relatively nonturbulent bodies of water are likely to be
A. obligate aerobes.
B. microaerophiles.
C. facultative anaerobes.
D. obligate anaerobes.
T F 47. During the lag phase of microbial growth, the cells are metabolically inactive.
48. Growth is said to be __________ when all cellular components are synthesized at constant rates relative to one another.
49. Unbalanced growth usually occurs when environmental conditions change.
50. Organisms that grow best at pH levels above 10 are called __________ __________.
51. Dark reactivation repairs thymine dimers by __________ and __________ in the absence of light.
T F 52. Ultraviolet radiation is generally more harmful than ionizing radiation.
T F 53. The rate growth of a given species of microorganism is dependent on the composition of the medium in which it is grown.
54. The amount of microbial mass (in grams) produced per gram of nutrient used is called the __________ yield.
55. The amount of microbial mass (in grams) produced per mole of nutrient used is called the __________ __________ yield.
56. An estimate of the number of reproductively capable cells in a sample based on the formation of colonies on solid growth media after plating dilute solutions is called a __________ cell count.
T F 57. Water activity is inversely proportional to osmotic pressure.
58. The length of the lag phase can vary depending on:
A. the condition of the microorganisms
B. the nature of the growth medium
C. Both a and b are correct.
D. Neither a nor b is correct.
59. Generation times can vary markedly depending on:
A. the species of a microorganism
B. the environmental conditions
C. Both a and b are correct.
D. Neither a nor b is correct.
60. Organisms with growth temperature maxima above 100C are referred to as
__________.
61. The destruction or removal of all viable organisms is called
A. disinfection.
B. antisepsis.
C. sterilization.
D. sanitization.
62. The reduction of the microbial population to safe levels is called
A. disinfection.
B. antisepsis.
C. sterilization.
D. sanitization.
63. The prevention of infection caused by microorganisms is called
A. disinfection.
B. antisepsis.
C. sterilization.
D. sanitization.
64. The killing of vegetative forms of pathogenic microorganisms (usually on inanimate objects) is called
A. disinfection.
B. antisepsis.
C. sterilization.
D. sanitization.
65. Microbial populations are reduced by __________ when exposed to a lethal agent.
A. a constant number
B. a constant fraction
C. a continuously increasing number
D. a variable number
66. Which of the following influence(s) the efficiency of an antimicrobial agent?
A. concentration of the agent
B. duration of exposure
C. temperature
D. All of these.
67. Which of the following environmental factors generally do(es) not have an impact on the efficiency of an antimicrobial agent?
A. Ph
B. viscosity
C. concentration of organic matter
D. All of these have an impact on the efficiency of an antimicrobial agent.
68. Which of the following is not a method of heat sterilization?
A. autoclaving
B. tyndallization
C. pasteurization
D. All of these are methods of heat sterilization.
69. Which of the following is MOST effective against resistant endospores?
A. autoclaving
B. tyndallization
C. pasteurization
D. All of these are very effective against resistant endospores.
70. Which of the following is not a form of ionizing radiation?
A. ultraviolet (UV) radiation
B. X radiation
C. gamma radiation
D. All of these are forms of ionizing radiation.
71. Which of the following is (are) a sterilizing gas(es) that can be used on heat-sensitive materials?
A. ethylene oxide
B. betapropiolactone
C. both ethylene oxide and betapropiolactone
D. neither ethylene oxide nor betapropiolactone
72. A (n) __________ is a chemical that can be used to sterilize materials.
A. oxidant
B. disinfectant
C. antiseptic
D. sterilant
73. Repeated cycles of exposure to elevated temperatures followed by incubation at 37C in order to kill heat resistant endospores are called ________.
A. tyndallization
B. fractional steam sterilization
C. Both a and b are correct.
D. Neither a nor b is correct.
74. The time required to kill 90% of the microorganisms or spores in a sample at a specified temperature is the
A. thermal death time (TDT).
B. thermal death point (TDP).
C. decimal reduction time (D value).
D. z value.
75. The shortest period of time needed to kill all organisms in a sample at a specified temperature is the
A. thermal death time (TDT).
B. thermal death point (TDP).
C. decimal reduction time (D value).
D. z value.
76. The increase in temperature needed to reduce the decimal reduction time to 10% of its value is the
A. thermal death time (TDT).
B. thermal death point (TDP).
C. decimal reduction time (D value).
D. z value.
77. Organic molecules that serve as wetting agents and emulsifiers and can be used as disinfectants if they are cationic are called
A. sterilants.
B. oxidants.
C. detergents.
D. soaps.
78. Sterilization is accomplished by __________ all viable microorganisms.
A. killing
B. removing
C. either killing or removing
D. neither killing nor removing
79. Moist heat sterilizes by
A. degrading nucleic acids.
B. denaturing proteins.
C. disrupting membranes.
D. All of these.
80. Which of the following is not a function of pasteurization?
A. killing pathogenic microorganisms
B. reducing the total microbial population
C. increasing the shelf life of the product
D. All of these are functions of pasteurization.
81. The disinfectant of choice for municipal water supplies is __________.
A. fluorine
B. chlorine
C. either fluorine or chlorine
D. neither fluorine nor chlorine
82. Disinfectants are generally regulated by the
A. Food and Drug Administration.
B. Environmental Protection Agency.
C. either Food and Drug Administration or Environmental Protection Agency.
D. neither Food and Drug Administration nor Environmental Protection Agency.
83. Antiseptics are generally regulated by the
A. Food and Drug Administration.
B. Environmental Protection Agency.
C. either Food and Drug Administration or Environmental Protection Agency.
D. neither Food and Drug Administration nor Environmental Protection Agency.
84. An agent that specifically kills fungi but not other kinds of microorganisms is best described as a
A. fungistatic agent.
B. germistatic agent.
C. fungicidal agent.
D. germicidal agent.
85. Which of the following generally do(es) not contribute to resistance to killing?
A. formation/existence of endospores
B. increased age of the culture
C. inherent/genetic differences among organisms
D. All of these may contribute to resistance to killing.
86. Depth filters sterilize materials passing through them by
A. exclusion of materials too large to penetrate the filter.
B. entrapment of material in the channels of the filter.
C. both exclusion of materials too large to penetrate the filter and entrapment of material in the channels of the filter.
D. neither exclusion of materials too large to penetrate the filter nor entrapment of material in the channels of the filter.
87. When antiseptics and disinfectants are compared, antiseptics are generally
A. less toxic.
B. more toxic.
C. equally as toxic.
D. unpredictable in toxicity.
88. Which of the following is true about filtration?
A. It can be used only to remove organisms from liquids.
B. It does not truly sterilize because it removes rather than kills microorganisms.
C. Both of these answers are correct.
D. Neither of these answers is correct.
89. When comparing dry heat and moist heat sterilization, dry heat is
A. faster.
B. slower.
C. equally as fast.
D. sometimes faster but sometimes slower.
90. Which will require a longer time to kill?
A. a larger population of microorganisms
B. a smaller population of microorganisms
C. Killing will be equally as rapid in a large or a small microbial population.
D. There is no way to predict which will require a longer kill time.
91. Although heavy metals are no longer widely used as germicides, __________ is still used to prevent ophthalmic gonorrhea in newborns.
A. lead acetate
B. copper sulfate
C. silver nitrate
D. mercuric chloride
92. Iodine can be complexed with an organic carrier to form water-soluble, stable complexes called __________, which release iodine slowly and eliminate most problems associated with iodine use.
A. iodides
B. tinctures
C. iodophores
D. iodochromes
93. The two most important alcohol germicides are __________ and __________.
A. ethanol; methanol
B. ethanol; isopropanol
C. methanol; butanol
D. methanol; isopropanol
94. Two methods of pasteurization are __________ and __________.
A. 63C for 30 minutes; 72C for 15 minutes
B. 63C for 30 minutes; 72C for 15 seconds
C. 63C for 30 seconds; 72C for 15 seconds
D. 63C for 15 minutes; 72C for 30 seconds
95. The process of heating milk products to 72C for 15 seconds in order to reduce the microbial population is called __________ pasteurization.
A. flash
B. fast
C. ultrafast
D. None of these are correct.
96. Which of the following represents the best definition for microbial death?
A. the organism will not grow on minimal medium
B. the organism will not grow on a medium that normally supports its growth
C. the organism no longer retains its original shape and structures
D. None of these adequately describe microbial death.
97. Which of the following is not a reason for studying methods of destroying microorganisms?
A. it makes possible microbiological research
B. preservation of food
C. prevention of disease
D. All of these are reasons for studying methods of destroying microorganisms.
98. An agent that kills bacteria is referred to as __________.
99. An agent that prevents the growth of bacteria without causing irreversible damage to the bacteria is referred to as __________.
100. Before being released for general use, antimicrobial agents should be tested for __________ and __________.
101. The __________ is a measure of disinfectant efficiency in which the disinfectant being evaluated is compared to phenol.
102. The type of filter used in a laminar flow biological safety cabinet is called a(n) __________ filter.
T F 103. Ultraviolet radiation is an effective means of sterilization but is limited to surfaces.
T F 104. Alcohols are widely used as antiseptics and disinfectants because they are effective against endospores as well as vegetative cells.
T F 105. Because filtration removes rather than destroys microorganisms, it does not truly sterilize the materials passing through the filter.
T F 106. Betapropiolactone is not as useful as ethylene oxide as a sterilizing agent because it does not penetrate materials as readily as ethylene oxide.
T F 107. The usefulness of an antiseptic or disinfectant is based solely on its effectiveness against pathogenic organisms.
T F 108. The rate of killing by an antimicrobial agent may slow when the microbial population has been greatly reduced because the remaining population may have a high proportion of resistant organisms.
T F 109. Ethylene oxide can be used to sterilize materials in sealed plastic wrap because it can penetrate the wrapping material.
T F 110. The phenol coefficient is a direct indication of disinfectant potency during normal use.
T F 111. Larger populations generally are killed as rapidly as smaller populations.
T F 112. Microorganisms show differential sensitivity to antimicrobial agents.
T F 113. Dry heat methods usually require lower temperatures and shorter exposure times than moist heat methods to achieve the same degree of killing because of the drying effects of this form of heat.
T F 114. Heavy metals are effective antimicrobial agents but are not widely used because of their high toxicity to humans.
T F 115. Quaternary ammonium compounds can be used as skin antiseptics because of their low toxicity.
T F 116. Although UV radiation is generally only effective against surface organisms, it can penetrate water to sterilize submerged items.