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Microbiology > Lecture 3 Microbial Growth 2.0 > Flashcards

Lecture 3 Microbial Growth 2.0 Flashcards

1
Q

Prokaryotic cells divide by

A

Binary fission

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2
Q

What type of growth do prokaryotic cells divide by?

A

Exponential growth: population doubles each division

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3
Q

What is an example of exponential growth starting with 2?

A

2, 4, 8, 16, 32

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4
Q

What time does it take for the population to double?

A

Generation time

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5
Q

Microbial growth is defined as an _______ in the number of cells in a population

A

Increase

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6
Q

What is Nt?

A

Number of cells in a population at time, t

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7
Q

What is N0?

A

Initial number of cells

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8
Q

What is n?

A

Number of generations at that point?

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9
Q

Most bacteria attach to surfaces and live in polymer encased communities called _________

A

Biofilms

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10
Q

Step 1 of biofilm

A

Free cells adhere to surface and multiple

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11
Q

Step 2 of biofilm

A

Release polymers to which unrelated cells may attach and grow

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12
Q

Step 3 of biofilm

A

Extra polymeric substances (EPS) give slimy appearances

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13
Q

Step 4 of biofilm

A

Nutrients and wastes pass through characteristic channels

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14
Q

Step 5 of biofilm

A

Cells communicate with one another via chemical channels

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15
Q

Dental plaque is _______
leads to ______ and _____

A

Biofilm
Tooth decay, gum disease

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16
Q

Most _________ seem to involve biofilm

A

infection

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17
Q

Microbes within bioflims are often ______ to immune system and antibiotics

A

Resistant

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18
Q

What is the industrial concern of biofilms?

A

Accumulation in pipes, dranes
- hundreds of times more resistant to disinfectants

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19
Q

Biofilms are helpful for what?

A

Bioremediation, wastewater treatment

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20
Q

Microorganisms regularly grow in close association with many different _______

A

species

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21
Q

Strict anareobes can grow in mouth if others consume ______

A

O2

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22
Q

Metabolic waste can serve as ______ of other

A

Nutrient

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23
Q

Interactions of mixed microbial communities are

A

Competitive

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24
Q

Some gram negative bacteria ______ system to inject toxic compounds directly into competing bacteria

A

Type VI secretion system

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25
Q

What is pure culture?

A

Population of cells derived from a single cell
allows study of a single species

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26
Q

What is an enrichment culture?

A

Used to isolate organism present as only a SMALL fraction of mixed population

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27
Q

In enrichment cultures, relative concentration of target organism increases or decreases?

A

Increases

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28
Q

What is direct cell counts

A

Total number
Living + dead

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29
Q

What are cell counting instruments?

A

Coulter counter, flow cytometer

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30
Q

How is total cell count determined? (equation)

A

1/volume held in square (in mL)
Then multiple that by number of cells

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31
Q

What is viable cell count?

A

Cells capable of multiplying

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32
Q

What media is used for viable cell counts?

A

selective, differential

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33
Q

What is plate counts

A

Single cell gives rise to coony

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34
Q

What shows how many cells were in a sample?

A

Number of colonies

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35
Q

Plate gets diluted to obtain how many colonies to produce a countable plate?

A

30 to 300

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36
Q

What to plate counts determine?

A

Colony forming unites (CFUs)

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37
Q

What is membrane filtration?

A

Known volume is passed through a sterile filter

Filter is incubated on agar medium

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38
Q

What does membrane filtration do?

A

It captures and concentrates microbes by filtration

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39
Q

How do you measure biomass?

A

Measure cell mass instead of number of cells

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40
Q

Turbidity of microbial suspension is proportional to what?

A

Concentration of cells

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41
Q

What measures biomass?

A

Spectrophotometer

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42
Q

What does a spectrophotometer show?

A

more cells present = less light

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43
Q

spectrophotometer measurement is effective only for what?

A

High concentration of cells

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44
Q

How is pure culture obtained?

A

Aseptic technique

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45
Q

Cells grown on pure culture contain nutrients dissolved in water, can be _______ or _______

A

liquir broth or solid gel

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46
Q

In a pure culture, single cell will multiply to form a _______

A

colony (aprox. 1 million cells)

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47
Q

What is used to solidify medium?

A

Agar

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48
Q

What can enter in a petri dish?

A

air, excludes contaminants

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49
Q

What is the simplest, most common method for isolating

A

Streak-plate method

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50
Q

After incubation of a streak plate, what do separate cells form

A

distinct, isolated colonies

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51
Q

a pure culture can be maintained as what/

A

stock culture

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52
Q

How is a stock culture maintained?

A

Stored in fridge as agar slant
cells can be frozen at -70 degrees for long term
mized with glycerol to prevent ice crystal formation
Can be freeze fried

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53
Q

What is a closed system?

A

Culture in which nutrients are not added, nor waste is remoced

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54
Q

What does a closed system include

A

Microorganisms grown on agar plates or in tubes or flasks of broth

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55
Q

What curve is seen in closed broth culture?

A

Growth curve

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56
Q

in a lag phase, what happens to number of cells?

A

Does not increase

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57
Q

what do the cells begin doing in a lag phase?

A

synthesizing enzymes required for growth

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58
Q

in an expontential (Log) phase, what rate do cells divide at?

A

constant rate

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59
Q

What is measured in the log phase?

A

Generation time

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60
Q

What does the log phase produce?

A

primary metabolites

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61
Q

What is produced as nutrients are depleted and wastes accumulate?

A

Secondary metabolites

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62
Q

What happens in the stationary phase
- nutrient levels are_______
- total numbers are _______
- continue to produce _______

A

too low to sustain growth
remain constant
secondary metabolites

63
Q

What happens in the death phase
- total number of cells _______
- cells die at a _______ rate
- grows _______ but slow

A

decrease
constant
exponential

64
Q

Phase of prolonged decline
- some fraction _______
- adapted to tolerate _______ conditions

A

survive
worsened

65
Q

position of a single cell in a colony determines its _______

A

environment

66
Q

What does the edge of a colony mean?

A

Little competition for O2 and nutrients

67
Q

What does the center of colony mean?

A

Depleted O2, accumulation of potentially toxic wastes

68
Q

Cells at edge of colony may show _______ growth

A

Exponential

69
Q

cells in the center of a colony are in the _______ phase

A

death

70
Q

What is an open system?

A

Culture to which nutrients are continually added and waste products removed

71
Q

What is a chemostat?

A

Provides an open system that can maintain continuous growth

72
Q

in a chemostat
- nutrient content and speed of addition can be controlled to achieve _______ growth rate and cell density

  • produces relatively _______ population to study response to different conditions
  • can maintain cells in _______ phase of growth to harvest commercially valuable products
A

constant

uniform

log

73
Q

What are extremophiles

A

Bacteria that live in harsh environments

74
Q

What are most of extremophiles?

A

Archaea

75
Q

What are the major factors that affect microbial growth?

A

Temperature, atmosphere, pH, water availability

76
Q

Degree of psychrophiles

A

-5 to 15

77
Q

degree of psychotrophs

A

15 to 30

78
Q

degree of mesophiles

A

25 to 45

79
Q

degree of thermophiles

A

45 to 70

80
Q

degree of hyperthermophiles

A

70>

81
Q

Where are psychotrophiles found?

A

arctic and antarctic regions

82
Q

What is psychrotrophs important for?

A

spoilage of refrigerated foods

83
Q

Thermophiles are common where?

A

hot springs, compost heaps

84
Q

Hypertherophiles are usually _______
found _______

A

Archaea
hydrothermal vents

85
Q

Solidified agar _______ gas diffusion

A

Slows

86
Q

In solidified agar,
- top is _______
- bottom is _______

A

Aerobic
Anaerobic

87
Q

What does the position of growth indicate?

A

O2 requirements

88
Q

obligate aerobes O2 requirement

A

Requires O2

89
Q

Facultative aerobes O2 requirement

A

Use O2 but don’t require it

90
Q

Obligate anaerobes O2 requirements

A

Cannot use O2

91
Q

Microaerophiles O2 requirement

A

Require small amounts of O2 only

92
Q

Aertolerant anaerobes (obligate fermenters)

A

Can grow O2 but don’t use it

93
Q

What are Reactive Oxygen Species

A

Harmful by-products of using O2 in aerobic respiration

94
Q

What are the two reactive oxygen species?

A

O2 and H2O2

95
Q

What is the affect of ROS?

A

Damages cellular components

96
Q

What bacteria don’t have the protective mechanisms against ROS?

A

obligate anaerobes

97
Q

Almost all organisms growing in presence of oxygen produce which enzyme?

A

Superoxide dismutase

98
Q

What does superoxide dismutase do?

A

Inactivates superoxide by converting it to O2 and H2O2

99
Q

What does catalse do?

A

Converts H2O2 —> O2 and H2O

100
Q

What is the exception to catalase?

A

Aerotolerant anaerobes

101
Q

Most bacteria have what pH?

A

neutral

102
Q

What do bacteria do if they are in an acidic environment?

A

Pump out protons H

103
Q

What do bacteria do if they are in an alkaline environment?

A

Bring in protons H

104
Q

Most microbes are

A

Neutrophiles

105
Q

What is the pH range of neutrophiles

A

5-8, optimum is 7

106
Q

Food can be preserved by increasing

A

Acidity

107
Q

What bacteria grows in stomach and produces urease to split urea into CO2 and ammonia?

A

H. pylori

108
Q

What does H. pylori do to the acidity of the surroundings?

A

Decreases

109
Q

What bacteria grow optimally at pH below 5.5

A

Acidophiles

110
Q

Which bacteria has an optimum pH of less than 1

A

Picrophilus oshimae

111
Q

What bacteria grow optimally at pH above 8.5

A

Alkaliphiles

112
Q

All organisms require what for growth?

A

water

113
Q

If solute concentration is higher outside of the cell, what happens?

A

Water diffuses out, osmosis

114
Q

Halotolerant

A

Withstands up to 10% sald

115
Q

What type of bacteria is staphylococcus in regards to salt tolerance?

A

Halotolerant

116
Q

What is halophiles

A

Requires high salt levels

117
Q

What are the major nutritional elements for prokaryotes

A

carbon, oxygen, hydrogen, nitrogen, sulfur, phosphorus, potassium, magnesium, calcium, iron

118
Q

What type of carbon to heterotrophs use?

A

Organic carbon

119
Q

What type of carbon to autotrophs use

A

inorganic carbon

120
Q

What is carbon fication

A

Converts inorganic carbon to organic carbon

121
Q

What is nitrogen required for?

A

Amino acids, nucleic acids

122
Q

What is nitrogen fixation?

A

Converts N2 gas to ammonia and incorporates into organic compounds

123
Q

Most organisms use what nitrogen?

A

ammonia or aminonitrogen

124
Q

Phospohrus and iron are _______ nutrients

A

Limiting

125
Q

What are growth factors

A

Organic molecules that an organism cannot synthesize

126
Q

What is fastidious

A

requires specific and many growth factors to survive

127
Q

What are phototrophs

A

obtain energy from sunlight

128
Q

What are chemotrophs

A

Extract energy from chemicals

129
Q

Photoautotrophs

A

Energy from sunlight, carbon from CO2

130
Q

Photoheterotrophs

A

Energy from sunlight, carbon from organic compounds

131
Q

Chemolithoautotrophs

A

Energy from inorganic compounds, carbon fro CO2

132
Q

Chemoorganoheterotrophs

A

Energy and carbon from organic compounds

133
Q

What is complex media

A

Contains variety of ingredients, exact composition is highly variable

134
Q

What is chemically defined media?

A

Composed of exact amounts of pure chemicals

135
Q

is chemically defined media or complex media faster?

A

Complex media… Chemically defined is slower as cells must synthesize components

136
Q

What can grow in complex and chemically defined media?

A

E. coli

137
Q

What is selective media

A

Inhibits growth of certain species in a mixed sample, allows growth of species of interest

138
Q

MacConkey agar is selective for what/

A

Gram negative rods

139
Q

MacConkey agar is differential for what?

A

Lactose fermentation

140
Q

What is selective media made up of?

A

Crystal violet that inhibits gram positive bacteria

bile salts that inhibit non-intestinal bacteria

141
Q

What is differential media?

A

Contains substance that microbes change in identifiable way

142
Q

What type of media is blood agar?

A

Differential

143
Q

in blood agar, what does beta hemolysis do?

A

produces clear zone

144
Q

In blood agar, what does alpha hemolysis do?

A

Produces zone of greenish partial clearing

145
Q

REFER TO SLIDE 38 for pictures
Which one could be MacConkey?
THIS IS ON EXAM…. MUST REVIEW

A

Differential

146
Q

Where can aerobes and facultative anaerobes be incubated?

A

in air, 20% O2

147
Q

Where do medically important bacteria (aerobes) grow best in?

A

Increased CO2

148
Q

Some medically important aerobes are

A

Capnophiles…REQUIRE increased CO2

149
Q

What method is used to incubate capnophiles?

A

Candle jar

150
Q

What does the microaerophilic require?

A

Lower O2 concentration achieved by candle jar

151
Q

How do you give optimal growth for microaerophilic bacteria?

A

Gas tight contain with chemical packet

152
Q

Obligate anaerobes are sensitive to

A

O2

153
Q

Anearobes are put into anaerobic containers if they can tolerate

A

Brief O2 exposure

154
Q

What are ways to detect cell products?

A

pH indicators, Durham tubes (inverted tubes to trap gas), CO2 productions

Microbiology (16 decks)

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