L7 Archaea and life in the extreme

Question 1

What kind of environments are archaea often associated with

Answer 1

Extreme

Question 2

What is likely to happen to the 3 domains of life tree as science evolves

Answer 2

Likely adapted into just 2 branches

Question 3

What is a characteristic component of archaeal cell walls

Answer 3

S-layer

Question 4

What is the role of the S-layer

Answer 4

Protection in harsh conditions

Question 5

Are archaea gram positive or gram negative

Answer 5

Can be either

Question 6

Give some examples of the metabolic processes carried out by archaea

Answer 6

Variant Entner-Doudorff, EMP pathways, metahnogenesis

Question 7

Do any other microbes produce methane through their energy production

Answer 7

No, just archaea

Question 8

Do archaea ususually have a cell wall

Answer 8

No

Question 9

What is most flexible: S-layer, peptidoglycan, double mmebrane structures

Answer 9

S-layer

Question 10

What is their range of growth temperature

Answer 10

-20 to 120 C

Question 11

Is sulphur metabolised anaerobically or aerobically

Answer 11

Both

Question 12

What temperature do Thaumarchaeota occur

Answer 12

Ambient - cold temperatures

Question 13

How many routes are there which produce methane for energy

Answer 13

Numerous

Question 14

What compounds are involved in the most common methanogenesis mechanism

Answer 14

Carbin dioxide and hydrogen to methane and water

Question 15

Does methanogenesis have a high or low yield of energy

Answer 15

Low
-∆G˚’

Question 16

Which environments can methanogens be found in

Answer 16

Wetlands
Paddy fields
Landfill
Polar permafrost
Animals (agriculture)
Sewage treatment
Marine sediments

Question 17

How do wetlands create an environment for methanogenesis

Answer 17

Rich in organic matter broken down by bacteria, poor oxygen diffusion creates anaerbic conditions

Question 18

How can polar permafrost create an ideal environment for methanogens

Answer 18

Retreating glaciers could cause mass release of methane as long term stored biomass will be exposed in wet conditions (ideal for methanogenesis)

Question 19

How is an extreme environment defined

Answer 19

Conditions damaging to most forms of life - often human centric

Question 20

What are some challenges of extreme cold

Answer 20

Enzyme mediated reactions are slower
Membranes become less fluid, reduce nutrient transport
Cold liquids are mroe viscous
Water freezes and causes ice crystals which are sharp and can pierce membranes

Question 21

What are some psychrophilic adaptations

Answer 21

Membrane fluidity increased
Cryoprotectant compounds
Low temp enzyme optima

Question 22

How can membrane fluidity be increased

Answer 22

Increase unsaturated and methyl branched fatty acids change to looser packing
More bonds = less rigid

Question 23

Give an example of cryoprotectant compounds

Answer 23

Anti-freeze proteins
Trehalose

Question 24

How can enzymes have a lower optimum temp

Answer 24

Increased flexibility due to reduced bonding between peptide chains, more accessible active site, amino acid selection

Question 25

What do colligative compounds do and give an example

Answer 25

Lower the freezing point of water through chemical properties
Trehalose

Question 26

How do microbes aid in rain formation

Answer 26

Rain must form / consense on something, this is usually a microbe

Question 27

How do microbes aid in snow formation

Answer 27

Microbes act as a nucelation o=point for water vapour

Question 28

What challenges do thermophiles face

Answer 28

Membranes become too fluid
Protein and nucleic acid denaturation
High temp drives oxygen depletion, environments often acidified

Question 29

What are some thermophillic adaptations

Answer 29

Saturated membrane lipids, ether bonding, monolayer and no cell wall
More stable proteins through bonding and anchoring
DNA binding proteins and supercoiling to prevent denaturation
Metabolisms favouring heat
Hear shoch responses in thermotolerant sp

Question 30

What metabolisms favour heat

Answer 30

Autotrophy
Lithotrophy
Anaerobic

Question 31

Why are piezophiles hard to study

Answer 31

They are at the bottom of the ocean and the change in pressure experienced when bringing them to the surface would destroy the cell

Question 32

What is one adaptation for living at high pressure

Answer 32

Specialised interconnected flattended cellular networks
Periplasm networks which share nutrition between cells

Question 33

Challenges of high salt environments

Answer 33

Desiccation / loss of water
Protein, membrane and DNA stability

Question 34

How can cells adapt to high salt

Answer 34

Aquaporins for water movement
Heat shock response

Question 35

What symporters do halophiles have

Answer 35

Sodium symports to echange Na+ for K+
Halophiles maintsain high intracellular potassium conc

Question 36

What is involved in the cell elvelope of halophiles and what does this achieve

Answer 36

Pseudopeptidoglycan for extra support

Question 37

What feature of halophile DNA helps avoid denaturation

Answer 37

High GC content (triple bonded)

Question 38

What metabolic method dominates Haloarchaea

Answer 38

Photoheterotrophy

Question 39

What structure is formed if an archaea becomes dessicated

Answer 39

Spores

Question 40

What is the pH range of E.coli

Answer 40

Tolerate pH2 to 11
Grow between 4.5 and 9

Question 41

Challenges of high alkalinity

Answer 41

Membrane, DNA and protein integrity
Maintaining a proton gradient in high OH-

Question 42

What causes a high alkaline environment

Answer 42

When there is no outflow of water