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Medical Microbiology > Microbial Growth - Chapter 3 > Flashcards

Microbial Growth - Chapter 3 Flashcards

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Biology 101 flashcards USMLE® Step 1 flashcards
1
Q

How do eukaryotic cells replicate?

A

Through meiosis and mitosis

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2
Q

Binary Fission Steps

A

Replicate DNA, cell elongation, cell separation

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3
Q

Cell Elongation

A

Formation of division septum, where 2 cells separate

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4
Q

What is made at the septum?

A

Cell membrane, cell wall, capsule

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5
Q

Cell Separation

A

How mitochondria divide

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6
Q

FtsZ Ring

A

Protein that forms a ring, tells the cell where to build layers so that it can separate -> will get smaller and smaller, and eventually the 2 layers will separate themselves

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7
Q

Cytokinesis

A

Septum formation is faster and simpler to replicate bacteria compared to mitosis

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8
Q

What is fragmentation common in?

A

Bacteria that form filaments

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9
Q

Fragmentation

A

Break into 2 pieces which expand to a longer filament, not very common, not just limited to bacteria

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10
Q

Budding

A

How yeast divide, asymmetric division -> big and little cell form

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11
Q

Bacterial Counts Formula

A

Nn = N0 x 2n

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12
Q

Nn

A

Total bacteria after n replications

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13
Q

N0

A

Starting number of bacteria

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14
Q

2n

A

n is the number of replications, can calculate by doing the time passed divided by the doubling time

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15
Q

Doubling Time of E. coli

A

20 minutes

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16
Q

Doubling Time of M. tuberculosis

A

15-20 hours

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17
Q

Doubling Time of M. leprae

A

14 days

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18
Q

Bacteria Growth Curve

A

Lag phase, log phase, stationary phase, death phase

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19
Q

Lag Phase

A

Gearing up for replication as they have a good amount of nutrients, cell size increases, increased metabolism, and protein production

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20
Q

Lag Phase Line

A

Straight as the bacteria count doesn’t change

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21
Q

Log Phase

A

Exponential growth, actively dividing, most susceptible to antibiotics and disinfectants

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22
Q

Log Phase Line

A

Line going up

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23
Q

What can antibiotics target?

A

DNA, RNA, or protein synthesis

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24
Q

Stationary Phase

A

Run out of nutrients and oxygen, build-up of waste, rate of division is equal to the rate of death, bacteria go into survival mode

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25
Q

Survival Mode for Bacteria

A

Sporulation starts, slow growth, produces metabolites that are released

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26
Q

Stationary Phase Line

A

Straight line

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27
Q

Death Phase

A

Increase of toxic waste that’s killing them, no nutrients left, bacteria undergo lysis to make nutrients for other bacteria to survive, spores are released, persister cells

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28
Q

Persister Cells

A

Cells that refuse to die, tend to have antibiotic resistance

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29
Q

What tends to have antibiotics?

A

Plasmids

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30
Q

Direct Methods to Count Bacteria

A

Petroff-Hausser Chamber/Coulter Counter

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31
Q

Indirect Methods to Count Bacteria

A

Plate count (CFU), most probably number, optical density, measure dry weight, measure ATP (cell viability)

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32
Q

Direct Counting of Bacteria

A

Zoom in on one slide of the cell and count the cells in that square, can make a dilution to help count, not very common

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33
Q

CFU (Plate Count)

A

Colony-forming units, using a dilution to approximate the amount of bacteria

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34
Q

CFU Process

A

Have a stock solution and make serial dilutions, from each dilution plate a portion and spread it to find individual colonies (want 30-300), count colonies in the plate then plug into a formula to get the total bacteria

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35
Q

What does each colony start as?

A

1 bacteria

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36
Q

Is CFU accurate?

A

It may be inaccurate as there are a lot of steps and we have the bacteria grow in between our stock culture and counting

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37
Q

Optical Density

A

Uses a spectrophotometer to measure turbidity in bacteria

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38
Q

Turbidity

A

Cloudiness

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39
Q

Spectrophotometer

A

Measure turbidity in bacteria and will get a specific absorbance as the light bounces off of the bacteria

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40
Q

What blank is used in the spectrophotometer for optical density?

A

A TSB media as the same media needs to be used in the blank and the samples

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41
Q

Why is optical light density indirect?

A

It doesn’t give an actual amount of bacteria, but rather the cloudiness of the solution

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42
Q

How can bacteria grow?

A

Freely grow or attach to a surface to grow

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43
Q

Planktonic

A

Free-floating

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44
Q

Sessile

A

Attach to a surface

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45
Q

What growth do bacteria need to be to live in a community?

A

Need to be sessile

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46
Q

How do bacteria talk to each other?

A

Through quorum sensing

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47
Q

Quorum Sensing

A

Coordination of activities in response to environmental stimuli

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48
Q

What does quorum sensing occur between?

A

Microbes of the same or different species

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49
Q

Autoinducers

A

Small chemicals that the bacteria release that interact with cells

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50
Q

Gram-Positive Bacteria Autoinducers

A

Short peptide

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51
Q

Gram-Negative Bacteria Autoinducers

A

N-acetylated homoserine lactone

52
Q

What needs to be done to make a community/biofilm?

A

The bacteria release autoinducers and must reach a threshold to make bacteria

53
Q

What are the steps of biofilm formation?

A

-Reversible attachment of planktonic cells
-First colonizers become irreversibly attached
-Growth and cell division
-Production of EPS and formation of water channels
-Attachment of secondary colonizers and dispersion of microbes to new sites

54
Q

When there are enough bacteria what do they secrete (2nd step)?

A

They secrete a matrix which holds them together

55
Q

Extrapolymeric Substance

A

EPS, holds things together, semipermeable substance, and communities are normally antibiotic resistant

56
Q

How do we get rid of the biofilm?

A

We have to disrupt the biofilm to get rid of it since it is antibiotic-resistant

57
Q

Why is there attachment of secondary colonizers and dispersion of microbes to new sites?

A

The bacteria will run out of nutrients and room

58
Q

Where do biofilms commonly form?

A

In water systems or on catheters

59
Q

What is one of the only extreme places bacteria can’t grow in?

A

Volcanoes

60
Q

What does thioglycolate medium do?

A

It sucks the oxygen out of the bottom of the media

61
Q

Obligate Aerobes

A

Require oxygen, growth on the top

62
Q

Obligate Anaerobes

A

Dislike oxygen, growth on the bottom

63
Q

Facultative Anaerobes

A

Prefers oxygen but can grow without it, the majority of growth on the top

64
Q

Aerotolerant Anaerobes

A

Indifferent to oxygen, equal growth throughout

65
Q

Microaerophiles

A

Like oxygen but not at the level of atmospheric oxygen, growth close to the top

66
Q

Capnophiles

A

Like carbon dioxide, dislike oxygen

67
Q

Where do capnophiles grow best?

A

Candle jars

68
Q

Candle Jar

A

Candle consumes oxygen providing the preferred environment

69
Q

Capnophiles Examples

A

Haemophilus sp. and Campylobacter jejuni

70
Q

What does Haemophilus sp. cause?

A

Influenza-like disease

71
Q

Where does Campylobacter jejuni live?

A

In the intestines

72
Q

Acid

A

Low pH

73
Q

Base

A

High pH

74
Q

Neutral

A

Middle pH, ~7

75
Q

Acidophile

A

Like acidic pH’s, 1-5.5

76
Q

Neutrophile

A

Like neutral pH’s, 5.5-8.5

77
Q

Alkaliphile

A

Like basic pH’s, 7.5-11.5

78
Q

Acidic Environments

A

Vagina and stomach

79
Q

Examples of acidophiles

A

Sulfolobus sp. and Lactobacillus sp.

80
Q

Examples of neutrophiles

A

E. coli and Salmonella sp.

81
Q

Examples of alkaliphiles

A

Vibrio cholera and Natronbacterium sp. (can survive the highest pH)

82
Q

Is it easier for bacteria to survive low or high pHs?

A

Low pHs as it is easier to pump out hydrogen ions

83
Q

Acidic - H or OH?

A

H

84
Q

Basic - H or OH?

A

OH

85
Q

pH effects on DNA

A

High pH breaks hydrogen bonds as the OH groups take the hydrogens

86
Q

pH effects on lipids

A

High pH hydrolyzes (breaks down) lipids

87
Q

pH effects on proteins

A

Slight changes in pH make a big difference (denature)
Changing ionization -> unfolding/misfolding -> degradation

88
Q

What is proton motive force also known as?

A

Electron transport

89
Q

High pH effects on proton motive force

A

At a high pH H binds to OH to form water instead of a gradient

90
Q

Low pH effects on proton motive force

A

At a low pH you need energy to pump H out to the high H environment, against the gradient causing a gradient problem

91
Q

Electron Transport

A

Pump H ions across the membrane and bring them back to make ATP

92
Q

What changes do acidophiles make to adapt to a changing pH?

A

Proteins have negatively charged surfaces, hydrogen efflux pumps, change the lipid composition of the plasma membrane to withstand low pH (modify lipids)

93
Q

What changes do alkaliphiles make to adapt to a changing pH?

A

Modified lipid and protein structures and modified proton motive force

94
Q

How do acidophiles make the protein have negatively charged surfaces?

A

They bring in positively charged particles

95
Q

Efflux Pump

A

Gets rid of hydrogen ions, takes energy

96
Q

What are the changes in ions in alkaliphiles?

A

The molecules used for electron transport may be changed to keep the gradient such as Na instead of H to prevent the formation of water.

97
Q

What temperature do psychrophiles like?

A

Cold temperatures around 10 degrees C

98
Q

What temperature do mesophiles like?

A

Temperatures around 37 degrees C

99
Q

What temperature do thermophiles like?

A

Temperatures around 65 degrees C

100
Q

What temperature do hyperthermophiles like?

A

Temperatures around 95 degrees C

101
Q

Psychrotolerant Temperatures

A

Can survive in the cold but prefer warmer temperatures, 3-35 degrees C

102
Q

Optimal Temperature of Psychrophiles

A

15 degrees C, but can survive below 0 degrees C

103
Q

At what temperature do psychrophiles die?

A

20 degrees C

104
Q

Where do psychrophiles live?

A

Cold lakes and the ocean floor

105
Q

Mesophiles Optimal Temperature

A

Moderate, around 20-40 degrees C

106
Q

Mesophile Examples

A

E. coli, Salmonella sp., and Lactobacillus sp.

107
Q

Where are thermophiles found?

A

Hot springs, geothermal soil, or compost

108
Q

Thermophiles Examples

A

Thermus aquaticus and Geobacillus sp.

109
Q

Where are thermophiles found?

A

Hydrothermal vents

110
Q

Hyperthermophiles Examples

A

Pyrobolus sp. and Pyrodictium sp. (can survive the autoclave)

111
Q

What are the effects of low temperatures on macromolecules?

A

Membranes slow down and lose fluidity, chemical reactions slow down, and diffusion slows down

112
Q

What are the effects of high temperatures on macromolecules?

A

Membrane lipids speed up which disrupts metabolic processes, proteins and nucleic acids will denature

113
Q

Psychrophiles Bonds

A

Decrease in secondary stabilizing bonds

114
Q

Hyperthermophiles Bonds

A

Increase in G-T content in DNA and increased secondary bonds in proteins

115
Q

Psychrophiles Flexibility

A

Proteins are highly hydrophobic due to increased flexibility

116
Q

Hyperthermophiles Saturation

A

Increase saturated/polysaccharide lipids to limit membrane fluidity

117
Q

Hyperthermophiles Amino Acid Usage

A

Alter amino acid usage to prevent protein denaturing

118
Q

Isotonic

A

No net movement of water, equal solutes

119
Q

Hypertonic

A

Higher concentration outside the cell, shrivel, water moves outside the cell

120
Q

Hypotonic

A

Higher concentration inside the cell, burst/lyse, water moves inside

121
Q

Halotolerant

A

High salt isn’t ideal, but it can grow

122
Q

Nonhalophile

A

Don’t like salt, isotonic environment, like 0.5% concentrations of salt

123
Q

Halophiles

A

Love salt, found in salt lakes and oceans, increased glycerol (prevents shrinking as water can’t move as well) and efflux pumps

124
Q

Barophiles

A

Need high atmospheric pressure for growth, found at the bottom of the ocean

125
Q

Photoautotrophs

A

Use light energy and CO2 is the primary carbon source

126
Q

Photoheterotrophs

A

Use light energy, but can’t use Co2 as a sole carbon source, use organic moelcules as their main carbon source

Medical Microbiology (4 decks)

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