E1 extremophiles - archaea

components of gram positive bacteria cell wall?

* inner cytoplasmic membrane
* periplasmic space
* outer peptidoglycan layer

components of gram -ve cell wall?

* inner cytoplasmic membrane
* periplasmic space
* peptidoglycan layer

This is then followed by another periplasmic space and then a lipopolysaccharide and protein outer membrane

archaea cell membrane?

* cytoplasmic membrane followed by a semi-rigid lattice of pseudomurein, sugars, proteins or glycoproteins
* NO peptidoglycan
* usually monolayer

Linkages in cell membranes? (archaea and bacteria)

* bacteria - ester linkage, lipid bilayer
* archaea - ether linkage, lipid monolayer - can also be bilayer

In what 4 ways are archaea lipids unique?

1. ether-linked (not ester)
2. side chains aren’t fatty acids, but branched isoprenes
3. different chiral forms of glycerol
4. some archaea possess lipid monolayers

Bacteria flagella?

* helical filaments - rotate providing motility
* produced by the addition of flagellin sub-units at the __tip__
* thick, hollow - allows flagellin sub-units to pass through

Archaea flagella?

* are superficially similar to bacteria but are considered non-homologous - evolve separately - no phylogenetic relationship
* grow by addition to the __base__

Last common ancestor branched to form…

bacteria and then archaea and eukaryotes

* very little horizontal gene transfer occurs between bacteria and archaea

polymerases in bacteria and archaea?

* archaea have complex DNA and RNA polymerases
* bacteria have simple

Histones in archaea?

* archaea contain histones while bacteria contain histone-like proteins

5 major groups of archaea?

* euryarchaeota
* crenarchaeota
* thaurmarchaeota
* koarchaeota
* nanoarchaeota

Euryarchaeota? - halobacteria?

* high salt environments
* don’t form resting stages or spores
* most are nonmotile, exist in water - are moved by flow of water
* cell wall is composed of glycoprotein and stabilized by Na+ to allow life in salt
* most are obligate aerobes

How do haloarchaea reproduce?

* by binary fission

Water balance in halophiles?

* need to maintain osmotic balance - this is usually achieved by accumulation or synthesis of compatible solutes
* pump large amounts of K+ into cell from environment.
* intracellular \[K+\] exceeds intracellular \[Na+\] and positive water balance is maintained

Proteins of halophiles?

* highly acidic
* contain fewer hydrophobic amino acids
* some haloarchaea are capable of light-driven synthesis of ATP

What are methanogenic archaea?

* microbes that produce CH4


* demonstrate a variety of cell wall chemistries

substrates for methanogens?

* obligate anaerobes
* other compounds e.g. glucose can be converted to methane, but only in cooperative reaction between methanogens and other anaerobic bacteria
* metabolic succession - methanogens in ruminant gut producing methane gas

Thermoplasma

* lack cell walls
* chemoorganotrophs, thermophillic, acidophillic
* facultative aerobes via sulfur respiration
* ferroplasma - oxidises Fe2+ to Fe3+, generates acid

thermoplasmatales membranes?

* allows for maintenance of positive osmotic pressure and tolerate high temp and low pH
* membrane contains lipopolysaccharide-like material (lipoglycan)
* has glycoproteins but not sterols

components of lipoglycan?

* tetraether lipid monolayer membrane with mannose and glucose

crenarchaeota

* obligate anaerobes
* chemoorganotrophs or chemolithotrophs - have diverse electron donors/acceptors
* most are hyperthermophiles - hot/cold

Sulfolobus?

* grows in sulfur-rich acidic hot springs
* aerobic chemolithotrophs that oxidise reduced sulfur to iron
* have phages and viruses - drive evolution

what are the upper temperature limits for life?

* lab suggests 140-150 C

How do protein monomers adapt to high temperatures?

* use of more heat-stable molecules - e.g. use of nonheme iron proteins instead of proteins that use NAD and NADH
* proteins tend to be globular and monomeric rather than forming big structures that are easily damaged

Change in protein folding in high temperatures?

* highly hydrophobic cores
* increased ionic interactions on protein surface

How is stability provided to DNA in hyperthermophiles?

* high intracellular solute levels stabilize DNA
* reverse DNA gyrase - introduces positive supercoilS into DNA - stabilizes DNA
* high intracellular levels of polyamines
* histones compact DNA into nucleosome-like structures