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Microbe-Environment Interactions Flashcards

(61 cards)

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1
Q

What are extremophiles?

A

Species which can survives under extreme conditions

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2
Q

How are microbes classified?

A

By temperature
By pH
By growth in salt
By effect of oxygen

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3
Q

What is minimum growth temperature?

A

The lowest temperature a species will grow at

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4
Q

What is maximum growth temperature?

A

The highest temperature at which growth is possible

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5
Q

What is optimum growth temperature?

A

The temperature at which the species grows best

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6
Q

What happens to growth rate above optimum growth temperature and why?

A

It declines rapidly because higher temperatures denature enzymes required for growth

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7
Q

What are organisms pH range?

A

2-3 units

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8
Q

What type of pathogens can tolerate low pH’s? Give an example.

A

Enteric pathogens

E.coli

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9
Q

What are neutrophils optimum growth pH?

A

5.5-8

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10
Q

What pH is referred to as optimum pH?

A

External pH

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11
Q

What pH must internal cells be maintained at?

A

pH 5-9

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12
Q

How much salt is in sea water?

A

3%

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13
Q

Requirement for salt is absolute. What does absolute mean?

A

It cannot be replaced by other ions

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14
Q

What are non-halophiles?

A

Microbes that do not grow well in salty conditions

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15
Q

What are halophiles?

A

Microbes that can tolerate salty conditions to a certain extent

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16
Q

What are moderate halophiles?

A

Microbes that grow well in salty conditions

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17
Q

What are extreme halophiles?

A

Microbes that thrive in salty conditions

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18
Q

What are obligate aerobes?

A

Microbes that require oxygen to survive

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19
Q

What are obligate anaerobes?

A

Microbes that are harmed by oxygen

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20
Q

What are facultative anaerobes?

A

Microbes that use oxygen when it is present but can grow without it

  • Fermentation
  • Anaerobic respiration
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21
Q

What are microaerophilic microbes?

A

Those which require oxygen but at lower levels than atmospheric oxygen

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22
Q

What are aerotolerant microbes?

A

Those which can not use oxygen for growth but are unaffected by its presence
- Respire anaerobically

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23
Q

When are superoxide free radicals produced?

A

During aerobic respiration

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24
Q

Why are superoxide free radicals toxic?

A

Because they are chemically unstable

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25
How do organisms that grow in atmospheric oxygen cope with toxic superoxide free radicals?
``` Superoxide dismutase (SOD) neutralises O2- Catalase converts toxic H2O2 to H2O ```
26
What environmental factors influence microbial growth?
``` Carbon sources Oxygen Temperature pH Salinity Water availability Sunlight (UV radiation) Predation ```
27
What are the problems surrounding microbial survival in high temperatures?
Proteins denature Small molecules are unstable DNA helix unwinds at high temperatures Membrane become more fluid
28
How might protein structure change in order to increase thermodynamic stability?
Proteins may fold differently
29
What property of amino acids lowers their tendency to unfold?
Hydrophobic core
30
What type of proteins might cells contain in order to protect themselves from high temperature?
Heat shock proteins | - Refold denatured proteins
31
What do cells contain that help DNA to remain coiled and functional in high temperatures?
Enzymes and DNA repair proteins - Reverse DNA gyrase Histone-like proteins and additional DNA binding proteins
32
Name a solute found in the cytoplasm that prevents unwinding and chemical damage of DNA.
Di-glycerol phosphate
33
How might membranes change in order to reduce fluidity?
More saturated and longer fatty acid chains | - These molecules pack more tightly making the membrane more stable
34
What do archaeal cell membranes lack?
Lipids
35
What are the problems surrounding microbial survival in low temperatures?
Decreased enzymatic activity Lower metabolic activity Slow rates of ion transport and diffusion
36
How might membranes change at low temperatures?
Increased unsaturated and shorted chain length fatty acids = more fluid Increased proportion of cyclic fatty acids
37
What types of proteins are produced at low temperatures? Give three examples
``` Cold shock proteins - RecA = involved in DNA repair - Hsc66 = maintains protein conformation - CspA = transcriptional factor Antifreeze proteins ```
38
What is the main problem surrounding microbial survival at low pH?
Maintaining pH homeostasis inside cells (pH 5-7)
39
What are aminophospholipids are how might they be affected at low pH?
Increased number | - They make membranes more positively charged
40
How are proton pumps affected at low pH?
Activated
41
How does membrane permeability to protons change at low pH?
Less permeable | - H+ influx inhibited by positive membrane potential
42
How is the number of membrane channels affected at low pH?
Reduced size and number of membrane channels
43
What cytoplasmic buffering molecules are produced at low pH?
Sugars | Amino acid derivatives
44
What is the main problem surrounding microbial survival at high salt concentrations?
Osmoregulation = maintaining turgor pressure inside cells
45
How does the cell protect proteins and enzymes at high salt concentrations?
Accumulation of K+ instead of Na+
46
Why is salt excluded from the cytoplasm at high salt concentrations and what is it replaced with?
Replaced with organic compatible solutes which do not interfere with enzymatic function
47
What is the main problem surrounding microbial survival at low water contents?
Desiccation = water loss
48
What do cells produced at low water contents?
``` Extracellular matrix (capsule) Osmoprotectants = trehalose More DNA repair proteins ```
49
What are xerophiles?
Organisms that are adapted to live in environments with low water activity
50
How can the growth of pathogens be controlled artificially?
By altering their certain aspects of their environment; - Heat - Cold - Acidity - Water activity - Chemicals
51
How is pathogen growth altered by heat?
Heat kills microbes by denaturing proteins and enzymes | Heat preserved canned goods are a good method of food preservation
52
What are the different ways in which heat can be altered in a pathogens environment?
``` Moist heat - Boiling - Steaming Pasteurisation Dry heat - Flaming - Sterilisation ```
53
How is pathogen growth altered by cold?
Microbes can be killed when ice crystals disrupt their cell membrane Usually cold temperatures slow or stop microbial growth
54
What microbe is the exception and is not affected by cold temperatures?
Listeria monocytogenes - Food borne bacterial pathogen - Can grow at 4 degrees
55
What temperature are microbes preserved at in labs?
-80 degrees with glycerol which acts as a cryptoprotectant
56
How is pathogen growth altered by acidity?
Foods often have a high or low pH in order to limit microbial growth Provides a way of preserving food
57
How is pathogen growth altered by water activity?
High water activity within foods leads to more rapid rancidity Lowering water activity is a way of preserving foods - Drying - Concentrating - Adding salt or sugar
58
How is pathogen growth altered by chemicals?
Antimicrobials Sterilants Disinfectants
59
What are antimicrobial agents?
Natural or synthetic chemicals that kill or inhibit growth of microbes - cidal = kill microbes - static = inhibit microbial growth
60
What are sterilants?
Destroy all forms of microbial life
61
What are disinfectants?
Kill microbial cells but do not always inactivate spores

Microbiology (18 decks)

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