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BIOC0034 > L7 : Life in Extreme Heat > Flashcards

L7 : Life in Extreme Heat Flashcards

(38 cards)

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1
Q

Parts of the Earth thermosphere?

A

Geothermal activity commonly associated with tectonic plate boundaries
- Tectonic plate ridges, pressure, continuous heat circulation
Land: volcanic areas, geysers, deserts
Ocean: vents, volcanoes

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2
Q

What extremophiles live within the thermosphere?

A

Hyperthermophiles: >80*c
Thermophiles: 45-80 *c

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3
Q

What are features of environments with extreme heat?

A
  • Environmental stability
  • No light
  • High temps
  • Desiccation (lack of water)
  • High pressure (particularly subterranean)
  • Low o2
  • High UV radiation
  • High toxicity (eg. heavy metals)
  • High salinity
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4
Q

What are mechanical stress challenges in extreme heat?

A

Fluid membrane
High diffusion
Loss of structural integrity

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5
Q

What are oxidative stress challenges in extreme heat?

A

Heavy metal toxicity
Metabolic byproducts (ROS)
Lipid oxidation
DNA/RNA damage

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6
Q

What are thermal stress challenges in extreme heat?

A

Impaired metabolism
Misfolded/denatured proteins

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7
Q

What are osmotic stress challenges in extreme heat?

A

Dehydration
High salt conc

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8
Q

Adaptations for organisms in extreme heat?

A

Physical: smaller size, flagella (bacteria/eukaryotes), archaella
Behavioural: thermotaxis, chemotaxis, symbiosis
Biochemical: stress response systems, cell structure changes

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9
Q

What are the cell membrane heat adaptations?

A

Adaptations to maintain membrane stability

  1. More membrane transporter channels (eg. Na+/K+): regulate osmotic balance
  2. More saturated phospholipids: tightly packed
  3. Longer fatty acid chains: increased VDWs and Tm
  4. More cyclised lipids (5C FAs): structurally rigid
  5. More glycolipids: increase membrane rigidity
  6. More HSPs and thermoprotectants
  7. More pigments: protection from UV
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10
Q

What are the cell membrane modifications in Archaea?

A
  1. Ether bonds between glycerol backbone and lipid chains: stronger
  2. Isoprenoid lipids instead of FAs: stronger
  3. Monolayer membranes: thinner, allow more exchange
  4. Extra glycolipids
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11
Q

How do cell membrane modifications in Archaea assist with stress response?

A

Lower phase transition temperature
Maintain membrane fluidity
Aid nutrient transport

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12
Q

List proteins and components are involved in the cell environment stress response?

A
  • Extracellular polymeric substances (EPS)
  • Ion pumps/transporters
  • Trehalose
  • Ribosomes
  • Polyols/ osmolytes
  • Compartmentalisation
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13
Q

How is EPS involved in environment stress response?

A

Form protective gel-like matrix
Retain water, prevent dehydration, form biofilms

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14
Q

How is compartmentalisation involved in environment stress response?

A

Compartmentalisation of proteins and metabolites into clusters offers localised protection against stress

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15
Q

How are ribosomes involved in environment stress response?

A

Ribosomes with rigid structure
Heat-stable
- Prevent denaturation
- Support efficient translation

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16
Q

How are pumps/transporters involved in environment stress response?

Study These Flashcards
A

Regulate intracellular concentrations (particularly cytoplasmic K+/Na+)
Osmotic balance

17
Q

What are 5 problems against DNA in extreme heats?

Study These Flashcards
A
  • High radiation
  • ROS production
  • Depurination
  • Deamination
  • Supercoiling stress
18
Q

What are DNA adaptations for extreme heat?

Study These Flashcards
A
  • Hypermethylation
  • High GC content
  • Histone-like proteins
  • DNA Gyrase
  • Increased K+ levels
  • Use of polyamines
  • Robust DNA repair
  • Thermostable polymerase
  • Small genome
19
Q

Explain adaptation of hypermethylation, GC, histone-like proteins for DNA?

Study These Flashcards
A

Hypermethylation
- Increase stability

GC content
- 3 H bonds
- Denaturation resistance

Histone-like
- Bacterial/archaeal analogues
- Bind and compact

20
Q

Explain adaptation of DNA gyrase for DNA

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A

Topoisomerase
- Introduces negative supercoils
- Reduce tension
- Prevent overwinding
- Maintain double helix

21
Q

Explain adaptation of intracellular K+ levels and polyamines for DNA?

Study These Flashcards
A

Intracellular K+ levels
- Neutralise backbone charge
- Stabilise double helix

Polyamines
- Reduce charge compulsion
- Promote compaction

22
Q

Explain adaptation of small genome size for DNA?

Study These Flashcards
A

Allows more efficient regulation and repair of genome
- Maintain integrity

23
Q

Explain adaptation of thermostable polymerases for DNA?

Study These Flashcards
A

Remain active at high temps
eg. Taq from Thermus Aquaticus

24
Q

How do proteins adapt against heat-structural damage?

Study These Flashcards
A

Tightly packed hydrophobic core
More strong H-bonds
Shorter, less flexible loops

25
How do proteins adapt against protein misfolding in extreme heat?
- Increased Arg, Pro, Glutamic acid (forms multiple H-bonds, salt bridges) - Increased Tyr, Trp, Phe (hydrophobic/aromatic help protein folding) - Reduced Gly (small compact, adds structural flexibility) - Reduced Ser and Thr (OH- at high temp increases susceptibility to denaturation) - Shorter surface loops - More disulfide bonds
26
How do proteins adapt against denaturation and aggregation in extreme heat?
- More chaperones to mediate folding (eg. HSPs) - More alpha helices in proteins (stability and compaction) - More thermoprotectants (eg. trehalose forming protective hydration cover) - More polyamines to reduce aggregation
27
How do proteins adapt against loss of enzyme activity?
- Increased thermal stability - Allosteric modulators (eg. ATP, AMP, NAD, metal ions) - PTMs (eg. phos, meth)
28
What is the purpose of modifying DNA and RNA nitrogenous bases?
- Stabilise nucleic acids - Protect from heat denaturation - Regulate gene expression - Involved in DNA repair
29
How are DNA bases modified?
Methylation of adenine and cytosine Note: A methylation not seen in mesophiles
30
How are RNA bases modified?
tRNA replacement of uridine with dihydrouridine (D) and/or pseudouridine More stable, avoiding deamination
31
How are sugars modified?
2'-O-ribose methylation Common in archaea
32
What evidence suggests LUCA was a hyperthermophile?
Reverse gyrase Only one type of reverse gyrase topoisomerase present in hyperthermophiles Universal presence (absence in mesophiles) suggests essential for survival in extreme heat Conservation suggests LUCA was heat adapted (sea vents?)
33
What are energy source adaptations?
- Cellular compartmentalisation to create cooler cellular microenvironments - Thermostable ATP-synthase - Store glycogen, lipids, starch, long chain FAs for prolonged energy release - Specialised thermostable enzymes for quick energy production + utilisation (glycolysis) - Use alternative energy sources (inorganic chemical compounds) - Use geothermal energy (hydrovents, hot springs) - Optimise light absorptions with thermally stable chlorophyll variants - Use anaerobic pathways to cope with lack of O2 - Symbiosis
34
Example of alternative metabolic resource?
H2 as energy source eg. hydrothermal vent - H2 metabolism quite likely the first energy source of earliest life on Earth
35
Difference between obligate and facultative?
Obligate - Need very high temperature for survival and growth Facultative - Can live and grow in both moderate and high temperatures
36
Temperature range for archaeal thermophiles and 2 examples
90-122 Sulfolobus acidocaldarius (first ever found) Methanopyrus kandleri (122)
37
Temperature range for bacteria and 2 examples?
45-95 Thermotogota (anaerobic, 95) Aquificota (aerobic, 95)
38
Example of Earth heat extreme as astrobiological model?
Jupiter 145 Gravitational contraction, heat, radiation

BIOC0034 (15 decks)

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