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Microbiology Exam 2 > Chapter 6 - Microbial Growth > Flashcards

Chapter 6 - Microbial Growth Flashcards

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1
Q

What is microbial growth?

A

An increase in cell size

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2
Q

What is the official name for increased cell size?

A

Hypertrophy

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3
Q

What is an increase in cell numbers?

A

Reproduction

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4
Q

What is another term for increase in cell number?

A

Hyperplasia

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5
Q

What are the two general categories of requirements for cell growth?

A

Physical and chemical factors

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6
Q

What is the lowest temperature at which organisms can grow?

A

Minimum growth temperature

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7
Q

What is Optimum growth temperature?

A

The temperature at which reproduction is fastest; favorable balance of cell death and reproduction

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8
Q

What is the highest temperature an organism can withstand?

A

Maximum growth temperature

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9
Q

What are the three physical requirements for growth?

A

Ideal temperature, pH, and osmotic pressure

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10
Q

What is the name for cold-loving organisms?

A

Psychrophiles

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11
Q

What temperature range do psychrophiles prefer?

A

0 - 20/30 C

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12
Q

What is the name of microorganisms that prefer moderate or warm temperatures?

A

Mesophiles

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13
Q

What heat range do mesophiles withstand?

A

20 - 40/45 C

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14
Q

What is the name of mesophiles that are specifically adapted to human body temperature?

A

Psychrotrophs

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15
Q

What is the name of heat-loving microorganisms?

A

Thermophiles

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16
Q

What heat range do thermophiles prefer?

A

40 - 80 C

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17
Q

If an organism thrives at temperatures above 65 C, what is it called?

A

Extreme thermophile

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18
Q

At what temperature do all microorganism die?

A

110 C; proteins denature

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19
Q

In what pH range do most bacteria grow?

A

6.5 - 7.5

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20
Q

What is the name of organisms that reproduce in an alkaline environment?

A

Alkalophiles

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21
Q

What pH do molds and yeasts prefer?

A

5-6 pH

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22
Q

What maintains pH homeostasis?

A

Buffers

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23
Q

At what pH can very few organisms grow?

A

Less than 4

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24
Q

What is the name of organisms that can grow at a pH less than 4?

A

Acidophilic

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25
Q

What preserves foods like pickles, sauerkraut, and cheese?

A

Acids produced during fermentation

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26
Q

What is tonicity?

A

The amount of solutes

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27
Q

Same amount of solute within and without

A

Isotonic

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28
Q

More solute outside of cell than within

A

hypotonic cell in a hypertonic solution

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29
Q

If put into a hypertonic solution, what will microbes undergo?

A

Plasmolysis

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30
Q

What 3 steps happen in plasmolysis?

A
  1. water leaves cell
  2. cell membrane separates from cell wall
  3. death
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31
Q

What is the name of organisms that survive in a hypertonic solution?

A

Halophiles

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32
Q

Is the mere presence of water enough to sustain microbial life?

A

No, water must be present and available

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33
Q

What are the three basic chemical requirements of organisms?

A
  1. Carbon
  2. Nitrogen
  3. Phosphorous and sulfur
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34
Q

What makes up 50% of a bacteria’s dry weight?

A

Carbon

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35
Q

What is carbon needed for in a cell?

A

All organic compounds

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36
Q

From where can carbon be obtained?

A

Organic compounds, CO2

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37
Q

What percent of a bacteria cell’s dry weight is nitrogen?

A

14

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38
Q

What is nitrogen used for in cells?

A

Nucleic acids, ATP, protein synthesis

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39
Q

Where is nitrogen obtained?

A

Soil, protein catabolism, nitrogen fixation

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40
Q

What genus uses nitrogen fixation to obtain nitrogen?

A

Rhizobium

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41
Q

What two elements make up 4% of a bacteria cell’s dry weight?

A

Phosphorous and sulfur

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42
Q

What are phosphorous and sulfur used for within a cell?

A

Nucleic acid synthesis, vitamin production, phospholipid synthesis

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43
Q

What is the cell membrane primarily composed of?

A

Phosphorous and sulfur

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44
Q

Where are phosphorous and sulfur obtained from?

A

Soil

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45
Q

If an organism needs oxygen to survive, what is its classification?

A

Obligate aerobe

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46
Q

If an organism requires no oxygen, what is its classification?

A

Obligate anaerobe

47
Q

If an organism grow better with oxygen but can survive without oxygen, what is it classified as?

A

Facultative anaerobe

48
Q

What class of organism does not grow in the presence of oxygen, but is not killed by oxygen?

A

Aerotolerant anaerobe

49
Q

What is a microaerphile?

A

An organism that needs only a little oxygen to survive

50
Q

What are unstable by-products of aerobic respiration?

A

Superoxide free radicals (O2-)

51
Q

What do all aerobes produce to break down oxygen?

A

Superoxide dismutase (SOD)

52
Q

What are the two enzymes that break down peroxide anions?

A

Catalase and peroxidase

53
Q

What is O2-2?

A

A peroxide anion

54
Q

What is a hydroxyl radical (OH-)?

A

A very strong oxidizing agent, by-product of oxygen use

55
Q

What is a highly reactive atom or molecule with unpaired electrons?

A

Free radicals

56
Q

What is the name of any material prepared for the growth of bacteria in the laboratory?

A

Growth medium

57
Q

What is a culture?

A

Microbes that grow an multiply in or on a culture medium

58
Q

What is agar?

A

A solidifying agent for a culture medium that comes from seaweed

59
Q

What is a chemically defined media?

A

A media whose exact chemical composition is known

60
Q

What is chemically defined media used to grow?

A

Fastidious organisms

61
Q

Which media decreases available oxygen?

A

Reducing media

62
Q

What is reducing media used to grow?

A

Anaerobic organisms

63
Q

What is complex media?

A

A media whose exact chemical composition is unknown

64
Q

What is grown on complex media?

A

Most bacteria and fungi

65
Q

What is the function of selective media?

A

To inhibit growth of certain organisms and encourage growth of others

66
Q

What kind of media is EMB?

A

Selective
Eosin Methylene Blue
Inhibit: G+
Select: G-

67
Q

What is Rose media selective for?

A

G+

68
Q

What is differential media?

A

It differentiates between different organisms growing on the same plate

69
Q

What allows growth of certain organisms on differential media?

A

Biochemical reactions

70
Q

What kind of media is Mannitol Salt Agar (MSA)?

A

Differential - looks for mannitol fermentation

71
Q

What is enriched media?

A

Media that has additional ingredients in it

72
Q

What kind of organisms are grown on enriched media?

A

Fastidious organisms

73
Q

What kind of media is a blood agar plate?

A

Enriched

74
Q

What is incomplete lysis of RBC called?

A

Alpha hemolysis

75
Q

What is complete lysis of RBC called?

A

Beta hemolysis

76
Q

What is Gamma Hemolysis?

A

No lysis of RBC

77
Q

Which media can be used to identify halophiles?

A

Mannitol Salt Agar

78
Q

Describe the basic composition of mannitol salt agar and what it tests for

A
  • high salt concentration (7.5%)
  • inhibits most bacteria
  • sugar Mannitol
  • pH indicator (phenol red, turns yellow in the acid of mannitol fermentation)
79
Q

What is a colony?

A

A group of cells of one microbial species

80
Q

What is a pure culture?

A

One strain of microorganism

81
Q

How are pure cultures usually obtained?

A

Streak plate

82
Q

What are two methods of preserving bacterial cultures?

A

Deep-freezing and lyophilization

83
Q

What temperature will deep-freeze an organism?

A

-50 c to -95 C

84
Q

What is lyophilization?

A

Deep freezing, dehydrating, then storing an org. in a sealed container; basically powered and can be rehydrated

85
Q

What is bacterial division?

A

Growth of bacterial cultures

86
Q

What is the primary method of bacterial division?

A

Binary fission (asexual)

87
Q

What are two methods of bacterial division other than binary fission?

A

Budding and fragmentation

88
Q

What is a species of organism in one location called?

A

Population

89
Q

What is the term for the hyperplasia of one species in one location?

A

Population growth

90
Q

What is another name for cell growth?

A

Hypertrophy

91
Q

What is the growth rate?

A

Hyperplasia per unit of time (hour, day, year, etc)

92
Q

What is the time required for the population to double called?

A

Generation time

93
Q

What is the generation time of bacteria?

A

20 minutes

94
Q

What kind of equation represents generation time?

A

Logarithmic

95
Q

What is the equation for generation time?

A

2^n, n = number of generations

96
Q

What are the four phases of growth?

A
  1. Lag Phase
  2. Log Phase
  3. Stationary Phase
  4. Death Phase
97
Q

In what phase of bacterial growth is the little or no hyperplasia, but lots of metabolic activity?

A

Lag phase

98
Q

What happens in the log phase of bacterial growth?

A

Number of new cells greatly surpasses the number of cell deaths

99
Q

What does the length of the log phase depend on?

A

Environmental availability

100
Q

What is the stationary phase and what causes it?

A

Cell growth stops due to lack of availability or presence of new inhibitors in environment

101
Q

During which phase are the number of new cells and dying cells equal?

A

Stationary phase

102
Q

What is the death phase of bacterial growth and what triggers it?

A

Lack of nutrients or presence of inhibitors causes the number of dying cells to surpass the number of new cells

103
Q

What are the 4 methods of direct measurement of microbial growth?

A
  1. Plate count
  2. Filtration
  3. Direct Microscopic Count (DMC)
  4. Serial Dilutions
104
Q

What does the plate count method count and what assumption is it working off of?

A

Counts visible colonies of viable microorganisms, assumes each bacterial cell will reproduce enough to form a colony

105
Q

What are the two methods of plate count?

A
  1. Pour plate - put microbe in empty petri dish, pour warm media over
  2. Spread plate method - Growth media is solid, inoculate on top
106
Q

How does filtration work to count microbial growth?

A

Run bacteria through membrane filter with different sized pores that maintain what you want to study

107
Q

What is the disadvantage of DMC?

A

Organisms can move between squares causing a miscount

108
Q

What is the maximum cell count for a serial dilution?

A

300 cells

109
Q

In which count of microbial growth is a concentrated sample diluted heavily before inoculation onto a spread plate?

A

Serial dilution

110
Q

What are the three indirect (guestimate) methods of counting microbial growth?

A
  1. Spectrophotometer - measures light and turbidity
  2. Metabolic activity of population
  3. Dry weight - used mostly for philamentus orgs. (like mold)
111
Q

What is the scientific name for a relationship between two organisms?

A

Symbiosis

112
Q

What is a relationship that benefits both organisms?

A

Mutualism

113
Q

What is a relationship where one organism benefits and the other is neutral?

A

Commensalism

114
Q

What is parasitism?

A

One organism benefits, the other suffers

Microbiology Exam 2 (4 decks)

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