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BIOL 2330 - microbiology > environmental requirements for growth > Flashcards

environmental requirements for growth Flashcards

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1
Q

list 6 factors that affect growth of microbes

A

pH, temperature, oxygen, solutes/water activity, pressure, radiation

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2
Q

what is the formula for pH

A

pH = -log[H+]

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3
Q

M of H+ at pH=0?

A

1 M

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4
Q

M of H+ at pH=14?

A

1 x 10^-14

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5
Q

what pH range do neutrophiles like

A

5.5-8.0

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6
Q

what pH range do acidophiles like

A

0.0-5.5

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7
Q

what pH range do alkaliphiles like

A

8.0-11.5

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8
Q

T or F: bacteria can adapt to environmental pH changes in order to survive

A

true

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9
Q

what is the role of acid shock proteins

A

protect bacteria when there’s acidity by preventing protein denaturation

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10
Q

how do acid shock proteins work

A

if the environment becomes acidic, then the bacteria will produce these proteins which help prevent protein denaturation + they can make use of proton pumps

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11
Q

what are the cardinal temperatures

A

minimum, optimum, and maximum

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12
Q

what is the minimum temperature for a bacteria

A

lowest temp at which the species will grow

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13
Q

what is the optimum temp for a bacteria

A

where the bacteria grows best

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14
Q

what is the maximum temp for a bacteria

A

the highest temp at which the bacteria will grow

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15
Q

is the optimum temp closer to the min or the max temp

A

closer to the max

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16
Q

what is the max temp for prokaryotes

A

121 C

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17
Q

why can’t bacteria grow below their min temp

A

membrane gelling will occur = transport processes are so slow that growth cannot occur

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18
Q

why does bacterial growth rate increase as the temp increases

A

enzymatic reactions are occurring at increasingly rapid rates

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19
Q

describe enzymatic reactions at the optimum temp

A

they’re occurring at the maximal possible rate

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20
Q

why can’t bacteria grow beyond their max temp

A

protein denaturation occurs, cytoplasmic membrane collapses, thermal lysis occurs

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21
Q

what is the general growth range for bacteria

A

30-40 C

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22
Q

list the 5 classes of organisms based on their temp ranges for growth

A

psychrophiles, psychrotrophs, mesophiles, thermophiles, hyperthermophiles

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23
Q

where are psychrophiles found

A

in the ocean depths or in arctic/Antarctic habitats, and in snow fields

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24
Q

what adaptations do psychrophiles have that allow them to survive in low temps

A

high levels of unsat FAs in PM, they contain antifreeze proteins which bind to ice crystals + prevent them from getting larger so they don’t pierce the PM and kill the organism

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25
Q

what are psychrotrophs important for

A

important in the spoilage of food

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26
Q

which class of bacteria based on temp range is the most common

A

mesophile

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27
Q

which class of bacteria based on temp range do all human pathogens fall under

A

mesophiles

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28
Q

where can thermophiles be found

A

organic compost piles, hot water lines, hot springs

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29
Q

what type of organism are thermophiles (ie pro or eu)

A

prokaryotic, but there are some algae and fungi

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30
Q

why are thermophiles important

A

this is where we get heat resistant enzymes from by isolating the DNA for PCR

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31
Q

where are hyperthermophiles found

A

in deep sea hydrothermal vents or hot springs associated with volcanic activity

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32
Q

how do hyperthermophiles adapt to such high temps

A

have heat-stable enzymes and protein synthesis systems that prevent denaturation. Proteins have lots of proline = makes enzymes more stable at high temps. Proteins have lots of H bonding. They have NAPS to help stabilize DNA (ie histones). Proteins may be stabilized by chaperones. FAs = saturated = tight packing = less fluid at high temps. Lipids are more branched, use ether linkages, and some have monolayers

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33
Q

what are the two groups of bacteria based on oxygen requirements

A

aerobes or anerobes

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34
Q

what are the 2 types of aerobes

A

obligate aerobes and microaerophiles

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35
Q

what are the 3 types of anaerobes

A

facultative anaerobe, aerotolerant anaerobe, and strict/obligate anaerobe

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36
Q

describe the oxygen needs of obligate aerobes

A

requires oxygen

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37
Q

how do we culture obligate aerobes

A

make use of a shaking incubator to give them lots of O2

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38
Q

describe oxygen needs of microaerophiles

A

requires O2 to grow, but at lower levels than atmospheric level (2-10% vs 20%)

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39
Q

how do we grow microaerophiles

A

use a CO2 generating packet to reduce O2 levels

40
Q

describe oxygen requirements for facultative anaerobes

A

does not require O2 for growth, but grows better when its present

41
Q

how do we grow facultative anaerobes

A

make use of a shaking incubator

42
Q

describe the oxygen requirements for aerotolerant anaerobes

A

O2 has no effect on growth. It grows equally in presence or absence

43
Q

describe the oxygen requirements for strict/obligate anaerobes

A

does not grow in the presence of O2

44
Q

how do we test for aerotolerance

A

make use of a eugon agar deep. Put the organism in, roll to mix, let harden overnight, then observe the growth

45
Q

describe the growth pattern within a eugon agar deep of an obligate aerobe

A

growth at the top

46
Q

describe the growth pattern within a eugon agar deep of a facultative anaerobe

A

growth at the top and a bit throughout

47
Q

describe the growth pattern within a eugon agar deep of an aerotolerant anaerobe

A

growth throughout

48
Q

describe the growth pattern within a eugon agar deep of an obligate anaerobe

A

growth at the bottom

49
Q

describe the growth pattern within a eugon agar deep of a microaerophile

A

growth just below the surface layer

50
Q

T or F: obligate anaerobes exposed to oxygen will die

A

true

51
Q

T or F: atmospheric oxygen + oxygen in chemical compounds is toxic to obligate anaerobes

A

false; these are not the forms of oxygen that are toxic

52
Q

what forms of oxygen are toxic to obligate anaerobes

A

singlet oxygen, superoxide radical, peroxide anion, and hydroxyl radical

53
Q

what is the name for the toxic forms of oxygen

A

Reactive Oxygen Species (ROS)

54
Q

what does ROS stand for

A

reactive oxygen species

55
Q

why are ROS toxic

A

they’re strong oxidizing agents and cause damage by oxidizing important compounds within the cell

56
Q

how is toxic oxygen produced

A

by ionizing radiation (ie gamma) or through normal metabolic reactions of bacteria

57
Q

name the two enzymes that protect microbes from toxic forms of oxygen

A

superoxide dismutase (SOD) and catalase

58
Q

what reaction does superoxide dismutase do

A

2 O2- + 2 H+ –> H2O2 + O2

59
Q

in the SOD reaction, 2 O2- + 2 H+ → H2O2 + O2, which part is toxic

A

peroxide ion: O2^2-

60
Q

what reaction does catalase do

A

2 H2O2 –> 2 H2O + O2

61
Q

how is water availability expressed

A

expressed as water activity, with the abbreviation aw

62
Q

what is the aw value for distilled water

A

1

63
Q

what aw value do most microbes require to grow well

A

aw = 0.98

64
Q

what occurs to the cell in a hypertonic environment

A

bacteria = plasmolyzed (water rushes out and PM pulls away from the cell wall)

65
Q

what is an osmophile

A

prefers to live in a hypertonic environment

66
Q

what solute type do osmophiles like

A

organic solutes like sugar or yeast (not things like salt)

67
Q

what is a halophile

A

an organism that requires NaCl at a concentration more than 0.2 M

68
Q

what concentration (minimum) of NaCl do halophiles need

A

more than 0.2 M

69
Q

T or F: osmophiles like salt

A

false; they only like organic solutes like sugar or yeast

70
Q

T or F: halophiles like salt (NaCl)

A

true

71
Q

what salt concentration range do extreme halophiles require

A

3-6.2 M

72
Q

what is a halotolerant organism

A

can grow in a wide range of NaCl concentrations

73
Q

what type of medium (in cell culturing) can be used for plating organisms with high salt tolerances

A

MSA: contains high salt concentration = selective medium

74
Q

what is a compatible solute

A

a molecule that doesn’t interfere with metabolism or growth when present at high intracellular concentrations

75
Q

why would microbes want to use compatible solutes

A

they accumulate to make the internal solute concentration higher than the external concentration, and this prevents water loss and instead water moves in

76
Q

what type of environment would cells want to have compatible solutes

A

hypertonic; bc compatible solutes prevent water loss

77
Q

where can cells get compatible solutes

A

they can produce them or get them from the environment

78
Q

give 4 examples of compatible solutes

A

KCl, choline, proline, glutamic acid

79
Q

what are KCl, proline, choline, and glutamic acid examples of

A

compatible solutes

80
Q

what would cells use to prevent the inward flow of too much water

A

mechanosensitive channels

81
Q

where are mechanosensitive channels located

A

in the PM

82
Q

describe how mechanosensitive channels work

A

they prevent the build up of pressure as water moves into the cell via channel opening and releasing solute

83
Q

what is the atmospheric pressure at sea level

A

1 atm

84
Q

what are barotolerant organisms

A

can withstand high pressure

85
Q

what are barophilic organisms

A

grows optimally at pressure greater than 1 atm

86
Q

1 atm = x pounds per square inch

A

14.7

87
Q

list 2 membrane adaptations to high pressure

A

more unsaturated fatty acids, length of fatty acids may shorten

88
Q

what is the major form of radion on earth

A

the sun

89
Q

what types of light do we get from the sun

A

UV, visible, infrared, and radio

90
Q

which type of light is responsible for heating the earth

A

infrared

91
Q

which type of light is used in photosynthesis

A

visible

92
Q

which type of light is dangerous + why

A

UV: as the wavelength decreases, the energy increases

93
Q

how can visible light cause damage to microbes

A

it can damage or kill microbial cells when present in sufficient intensity. Bacteria contain pigments that can absorb he light energy and produce singlet oxygen (toxic)

94
Q

which form of toxic oxygen can bacteria produce when they absorb light energy

A

singlet oxyegn

95
Q

how do airborne bacteria + bacteria on exposed surfaces protect themselves from light?

A

they have carotenoid pigments that absorb energy from singlet oxygen, thereby preventing its toxic effects

BIOL 2330 - microbiology (30 decks)

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