L7 Archaea and life in the extreme Flashcards
What kind of environments are archaea often associated with
Extreme
What is likely to happen to the 3 domains of life tree as science evolves
Likely adapted into just 2 branches
What is a characteristic component of archaeal cell walls
S-layer
What is the role of the S-layer
Protection in harsh conditions
Are archaea gram positive or gram negative
Can be either
Give some examples of the metabolic processes carried out by archaea
Variant Entner-Doudorff, EMP pathways, metahnogenesis
Do any other microbes produce methane through their energy production
No, just archaea
Do archaea ususually have a cell wall
No
What is most flexible: S-layer, peptidoglycan, double mmebrane structures
S-layer
What is their range of growth temperature
-20 to 120 C
Is sulphur metabolised anaerobically or aerobically
Both
What temperature do Thaumarchaeota occur
Ambient - cold temperatures
How many routes are there which produce methane for energy
Numerous
What compounds are involved in the most common methanogenesis mechanism
Carbin dioxide and hydrogen to methane and water
Does methanogenesis have a high or low yield of energy
Low
-∆G˚’
Which environments can methanogens be found in
Wetlands
Paddy fields
Landfill
Polar permafrost
Animals (agriculture)
Sewage treatment
Marine sediments
How do wetlands create an environment for methanogenesis
Rich in organic matter broken down by bacteria, poor oxygen diffusion creates anaerbic conditions
How can polar permafrost create an ideal environment for methanogens
Retreating glaciers could cause mass release of methane as long term stored biomass will be exposed in wet conditions (ideal for methanogenesis)
How is an extreme environment defined
Conditions damaging to most forms of life - often human centric
What are some challenges of extreme cold
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
What are some psychrophilic adaptations
Membrane fluidity increased
Cryoprotectant compounds
Low temp enzyme optima
How can membrane fluidity be increased
Increase unsaturated and methyl branched fatty acids change to looser packing
More bonds = less rigid
Give an example of cryoprotectant compounds
Anti-freeze proteins
Trehalose
How can enzymes have a lower optimum temp
Increased flexibility due to reduced bonding between peptide chains, more accessible active site, amino acid selection
What do colligative compounds do and give an example
Lower the freezing point of water through chemical properties
Trehalose
How do microbes aid in rain formation
Rain must form / consense on something, this is usually a microbe
How do microbes aid in snow formation
Microbes act as a nucelation o=point for water vapour
What challenges do thermophiles face
Membranes become too fluid
Protein and nucleic acid denaturation
High temp drives oxygen depletion, environments often acidified
What are some thermophillic adaptations
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
What metabolisms favour heat
Autotrophy
Lithotrophy
Anaerobic
Why are piezophiles hard to study
They are at the bottom of the ocean and the change in pressure experienced when bringing them to the surface would destroy the cell
What is one adaptation for living at high pressure
Specialised interconnected flattended cellular networks
Periplasm networks which share nutrition between cells
Challenges of high salt environments
Desiccation / loss of water
Protein, membrane and DNA stability
How can cells adapt to high salt
Aquaporins for water movement
Heat shock response
What symporters do halophiles have
Sodium symports to echange Na+ for K+
Halophiles maintsain high intracellular potassium conc
What is involved in the cell elvelope of halophiles and what does this achieve
Pseudopeptidoglycan for extra support
What feature of halophile DNA helps avoid denaturation
High GC content (triple bonded)
What metabolic method dominates Haloarchaea
Photoheterotrophy
What structure is formed if an archaea becomes dessicated
Spores
What is the pH range of E.coli
Tolerate pH2 to 11
Grow between 4.5 and 9
Challenges of high alkalinity
Membrane, DNA and protein integrity
Maintaining a proton gradient in high OH-
What causes a high alkaline environment
When there is no outflow of water
