Term
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Definition
Lack peptidoglycan (stain g+ or g-)
Pseudomurein, polysaccharides, S-layer (protein or glycoproteins)
Ether linkages in membrane lipids; phytanyl, biphytanyl side chains
Differences in RNA polymerase, protein synthesis
Physiologically diverse
Occur just about everywhere (20% of marine prokaryotes) |
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Term
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Definition
Archaea is split into two major groups:
Euryarchaeota
Crenarchaeota |
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Term
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Definition
Physiologically diverse group of Archaea
Many inhabit extreme environments
- examples: high temperatures, high salt, high acid |
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Term
| Haloarchaea (extreme halophiles) |
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Definition
Key genera: Halobacterium, Haloferax, Natronobacterium
Have a requirement for high salt concentrations
- typically require at least 1.5M (9%) NaCl for growth
Cell wall is composed of glycoprotein and stabilized by Na+
Found in artificial saline habitats (e.g., salted foods), solar salt evaporation ponds, and salt lakes |
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Term
| Water balance in extreme halophiles |
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Definition
Halophiles need to maintain osmotic balance
- this is usually achieved by accumulation or synthesis of compatible solutes
Halobacterium species instead pump large amounts of K+ into the cell from the environment
- intracellular K+ concentration exceeds extracellular Na+ concentration and positive water balance is maintained |
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Term
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Definition
Are highly acidic
Contain fewer hydrophobic amino acids and lysine residues |
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Term
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Definition
Habitats and energy metabolism
- inhabit temperature extremes
- most cultured representatives are hyperthermophiles
-- found in extreme heat environments
-- most are obligate anaerobes |
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Term
| Temperature limits for microbial life |
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Definition
What are the upper temperature limits for life?
- new species of thermophiles and hyperthermophiles being discovered
- laboratory experiments with biomolecules suggest 140-150C |
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Term
| Molecular adaptations to life at high temperatures |
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Definition
Stability of monomers
Protein folding and thermostability
Chaperonins
DNA stability
Lipid stability
SSU rRNA stability |
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Term
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Definition
Protective effect of high concentration of cytoplasmic solutes
Use of more heat-stable molecules
- for example, use of nonheme iron proteins instead of proteins that use NAD and NADH |
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Term
| Protein folding and thermostability |
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Definition
Amino acid composition similar to that of non-thermostable proteins
Structural features improve thermostability
- highly hydrophobic cores
- increased ionic interactions on protein surfaces |
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Term
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Definition
| Class of protein that refold partially denatured proteins |
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Term
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Definition
High intracellular solute levels stabilize DNA
Reverse DNA gyrase
- introduces positive supercoils into DNA
-- stabilizes DNA
-found only in hyperthermophiles
High intracellular levels of polyamines (e.g., putrescine, spermidine) stabilize DNA and RNA
DNA-binding proteins (histones) compact DNA into nucleosomes-like structures |
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Term
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Definition
| Possess dibiphantanyl tetraether type lipids; form a lipid monolayer membrane structure |
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Definition
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