environmental requirements for growth

Question 1

list 6 factors that affect growth of microbes

Answer 1

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

Question 2

what is the formula for pH

Answer 2

pH = -log[H+]

Question 3

M of H+ at pH=0?

Answer 3

1 M

Question 4

M of H+ at pH=14?

Answer 4

1 x 10^-14

Question 5

what pH range do neutrophiles like

Answer 5

5.5-8.0

Question 6

what pH range do acidophiles like

Answer 6

0.0-5.5

Question 7

what pH range do alkaliphiles like

Answer 7

8.0-11.5

Question 8

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

Answer 8

true

Question 9

what is the role of acid shock proteins

Answer 9

protect bacteria when there’s acidity by preventing protein denaturation

Question 10

how do acid shock proteins work

Answer 10

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

Question 11

what are the cardinal temperatures

Answer 11

minimum, optimum, and maximum

Question 12

what is the minimum temperature for a bacteria

Answer 12

lowest temp at which the species will grow

Question 13

what is the optimum temp for a bacteria

Answer 13

where the bacteria grows best

Question 14

what is the maximum temp for a bacteria

Answer 14

the highest temp at which the bacteria will grow

Question 15

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

Answer 15

closer to the max

Question 16

what is the max temp for prokaryotes

Answer 16

121 C

Question 17

why can’t bacteria grow below their min temp

Answer 17

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

Question 18

why does bacterial growth rate increase as the temp increases

Answer 18

enzymatic reactions are occurring at increasingly rapid rates

Question 19

describe enzymatic reactions at the optimum temp

Answer 19

they’re occurring at the maximal possible rate

Question 20

why can’t bacteria grow beyond their max temp

Answer 20

protein denaturation occurs, cytoplasmic membrane collapses, thermal lysis occurs

Question 21

what is the general growth range for bacteria

Answer 21

30-40 C

Question 22

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

Answer 22

psychrophiles, psychrotrophs, mesophiles, thermophiles, hyperthermophiles

Question 23

where are psychrophiles found

Answer 23

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

Question 24

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

Answer 24

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

Question 25

what are psychrotrophs important for

Answer 25

important in the spoilage of food

Question 26

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

Answer 26

mesophile

Question 27

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

Answer 27

mesophiles

Question 28

where can thermophiles be found

Answer 28

organic compost piles, hot water lines, hot springs

Question 29

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

Answer 29

prokaryotic, but there are some algae and fungi

Question 30

why are thermophiles important

Answer 30

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

Question 31

where are hyperthermophiles found

Answer 31

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

Question 32

how do hyperthermophiles adapt to such high temps

Answer 32

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

Question 33

what are the two groups of bacteria based on oxygen requirements

Answer 33

aerobes or anerobes

Question 34

what are the 2 types of aerobes

Answer 34

obligate aerobes and microaerophiles

Question 35

what are the 3 types of anaerobes

Answer 35

facultative anaerobe, aerotolerant anaerobe, and strict/obligate anaerobe

Question 36

describe the oxygen needs of obligate aerobes

Answer 36

requires oxygen

Question 37

how do we culture obligate aerobes

Answer 37

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

Question 38

describe oxygen needs of microaerophiles

Answer 38

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

Question 39

how do we grow microaerophiles

Answer 39

use a CO2 generating packet to reduce O2 levels

Question 40

describe oxygen requirements for facultative anaerobes

Answer 40

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

Question 41

how do we grow facultative anaerobes

Answer 41

make use of a shaking incubator

Question 42

describe the oxygen requirements for aerotolerant anaerobes

Answer 42

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

Question 43

describe the oxygen requirements for strict/obligate anaerobes

Answer 43

does not grow in the presence of O2

Question 44

how do we test for aerotolerance

Answer 44

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

Question 45

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

Answer 45

growth at the top

Question 46

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

Answer 46

growth at the top and a bit throughout

Question 47

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

Answer 47

growth throughout

Question 48

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

Answer 48

growth at the bottom

Question 49

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

Answer 49

growth just below the surface layer

Question 50

T or F: obligate anaerobes exposed to oxygen will die

Answer 50

true

Question 51

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

Answer 51

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

Question 52

what forms of oxygen are toxic to obligate anaerobes

Answer 52

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

Question 53

what is the name for the toxic forms of oxygen

Answer 53

Reactive Oxygen Species (ROS)

Question 54

what does ROS stand for

Answer 54

reactive oxygen species

Question 55

why are ROS toxic

Answer 55

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

Question 56

how is toxic oxygen produced

Answer 56

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

Question 57

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

Answer 57

superoxide dismutase (SOD) and catalase

Question 58

what reaction does superoxide dismutase do

Answer 58

2 O2- + 2 H+ --> H2O2 + O2

Question 59

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

Answer 59

peroxide ion: O2^2-

Question 60

what reaction does catalase do

Answer 60

2 H2O2 --> 2 H2O + O2

Question 61

how is water availability expressed

Answer 61

expressed as water activity, with the abbreviation aw

Question 62

what is the aw value for distilled water

Answer 62

1

Question 63

what aw value do most microbes require to grow well

Answer 63

aw = 0.98

Question 64

what occurs to the cell in a hypertonic environment

Answer 64

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

Question 65

what is an osmophile

Answer 65

prefers to live in a hypertonic environment

Question 66

what solute type do osmophiles like

Answer 66

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

Question 67

what is a halophile

Answer 67

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

Question 68

what concentration (minimum) of NaCl do halophiles need

Answer 68

more than 0.2 M

Question 69

T or F: osmophiles like salt

Answer 69

false; they only like organic solutes like sugar or yeast

Question 70

T or F: halophiles like salt (NaCl)

Answer 70

true

Question 71

what salt concentration range do extreme halophiles require

Answer 71

3-6.2 M

Question 72

what is a halotolerant organism

Answer 72

can grow in a wide range of NaCl concentrations

Question 73

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

Answer 73

MSA: contains high salt concentration = selective medium

Question 74

what is a compatible solute

Answer 74

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

Question 75

why would microbes want to use compatible solutes

Answer 75

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

Question 76

what type of environment would cells want to have compatible solutes

Answer 76

hypertonic; bc compatible solutes prevent water loss

Question 77

where can cells get compatible solutes

Answer 77

they can produce them or get them from the environment

Question 78

give 4 examples of compatible solutes

Answer 78

KCl, choline, proline, glutamic acid

Question 79

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

Answer 79

compatible solutes

Question 80

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

Answer 80

mechanosensitive channels

Question 81

where are mechanosensitive channels located

Answer 81

in the PM

Question 82

describe how mechanosensitive channels work

Answer 82

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

Question 83

what is the atmospheric pressure at sea level

Answer 83

1 atm

Question 84

what are barotolerant organisms

Answer 84

can withstand high pressure

Question 85

what are barophilic organisms

Answer 85

grows optimally at pressure greater than 1 atm

Question 86

1 atm = x pounds per square inch

Answer 86

14.7

Question 87

list 2 membrane adaptations to high pressure

Answer 87

more unsaturated fatty acids, length of fatty acids may shorten

Question 88

what is the major form of radion on earth

Answer 88

the sun

Question 89

what types of light do we get from the sun

Answer 89

UV, visible, infrared, and radio

Question 90

which type of light is responsible for heating the earth

Answer 90

infrared

Question 91

which type of light is used in photosynthesis

Answer 91

visible

Question 92

which type of light is dangerous + why

Answer 92

UV: as the wavelength decreases, the energy increases

Question 93

how can visible light cause damage to microbes

Answer 93

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)

Question 94

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

Answer 94

singlet oxyegn

Question 95

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

Answer 95

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