10. Extremophiles I Flashcards
1
Q
what is an extremophile?
A
- organism that thrives under extreme conditions
- anthropocentric term, judged based of human extreme
2
Q
what examples of extremophiles are there?
A
- thermophiles
- psycrophiles
- acidophiles
- alkaliphiles
- halophiles
- piezophiles
- polyextemophiles (themophilic acidophile)
3
Q
what is th challenge of life at high temperatures?
A
- denaturation
4
Q
what organism lives at extreme hot temperatures?
A
- thermophilic
- habitat in excess of 40 degrees
- geological thermal sites (volcanoe, hot spring, deep-sea hydrothermal vents)
5
Q
what are the types of thermophiles?
A
- psychrophile
– grow at 0 and below; optimum at 15 - mesophile
– optimum from 20 - 45 - thermophile
– optimal growth at 40 or over - hyoerthermophile
– optimal at 80 or over
6
Q
how have thermophiles adapted to live at high temperatures?
A
- stabilisation of membrande fluidity (increasing fatty acid chain length and branching)
– presence of sat. fatty acids in membrane lipids
– sat. fatty acids form stronger hydophobic environment helping membrane stability - higher amount of cystine amino acids (form disulfide bonds)
– critical amino acid substitutions allowing folding increasing heat stability - genes coding for HSP60 proteins (refold unpregulated proteins)
7
Q
what are the consituents of psycrophiles? **
A
- optimum growth at 15
– usually inhibit at low temperatures - eg..
8
Q
what are the psycrophilic adaptations?
A
- lipid membranes more unsaturated fatty acids
– more fluid - upregulation of cold/heat-shock protein expressions
- accumulation of cryoptotectants
– glycine; betaine; glycerol; trehalose; sucrosel mannitol; sorbitol
– cryoprotectants reduce freezing pt. of cytoplasm
– prevent macromolecule aggregation
– scavenge free radicals and stabilise cellular membranes under cold conditions
9
Q
what are acidophiles?
A
- have optimum pH less than 3 for growth
- live in acidic environments
10
Q
what are acidophiles role in sulfur cycling and acid mine drainage?
A
- Ferroplasma
– pH = 0
– use sulphur cycling to transform sulphide from metal ores to sulphuric acid
11
Q
how have acidophiles adapted?
A
- reverse membrane potential to partially deflect inward flow of protons
– potential mechanism of generating reversed membrane potential is by potassium transport
– predominance of potassium-transporting ATPases found in genomes - evolved highly impermeable cell membranes to retard influx of protons inot cell
– increased membrane rigidity by increasing no. of longer chained fatty acids across lipid bilayer
– and lipid order, chain saturation, cyclization, and hopanoids - pH gradient maintained through active proton export by transporters
- sequencing of several genome sequences
– higher proportion of secondary transporters in neutralophiles
– reduce energy demands of pumping necessary solutes and nutrients into cell - cytoplasmic buffers
– contain basic amino acids to keep pH constant and neutralise acidic effect - presence of enzymes/chemicals capable of bidning and sequestering protons
- larger proportion of DNA and protein repair systems present
12
Q
what are alkalophilic organisms?
A
- pH > 9
13
Q
what are the effects of high pH on organisms?
A
- membrane damage
- DNA damage
- lowered enzyme activity
14
Q
how have cells adapted to high pH conditions?
A
- elevated levels of transporters and enzymes
– promote proton capture and retention - metabolic changes
– lead to increased acid production
15
Q
what are halophiles?
A
- hypersaline conditions (salt >3,5%)
