L13 Flashcards
What similarities are there between bacterium and archaeon?
Lack of nucleus and membrane bound organelles, 70s ribosomes, unicellular.
What did Woese et al find?
Some 16s sequences from prokaryotes differ to other prokaryotes
What is bacteria and archaea common ancestor?
LUCA
What shows similarities with archaea?
Eukaryotes and bacteria
What are the similarities between archaea and eukaryotes?
They have similar molecular pathways, archaeal DNA polymerases and RNA polymerase are similar to eukaryotes. RNAP in archaea is like RNAP2 in eukaryotes.
What are archaea unique in?
None of the known archaea species are pathogens. Their cell envelope
What is the bacterial cell envelope?
The plasma membrane of a bacterial cell is a phospholipid bilayer : a glycerol phosphate head attached to two fatty acids.
What is the archaea cell envelope?
The cell membrane of archaeal cells is a glycerol phosphate head attached to two isoprenoids.
What does a isoprenoid unit consist of?
5 carbon atoms arranged in a specific pattern.
What can the archaea glycerol phosphate head and two isoprenoid cell envelope be replaced by?
A phospholipid monolayer
What is the difference between isoprenoid bilayers and monolayers compared to bacterial phospholipid membrane?
They are more stable at low pH, high t, salt concs than bacterial phospholipid membrane. Allowing them to withstand harsher environments.
What is the cell wall of archaeal cells?
Polysaccharides or peptidoglycan (pseudomurein/pseudopeptidoglycan)
What is pseudomurein/pseudopeptidoglycan made of?
N-acetylglucosamine + N-acetyltalosaminuric acid. They are linked by beta 1-3 glycosylic bonds, this makes it lysozyme insensitive.
What are wall-less archaea
Some archaea don’t have pseudomurein cell walls. They protect the cell membrane with a S-layer consisting of proteins/glycoproteins interlocked to form a lattice.
For a long time archaea were restricted to two phyla called?
Eukaryarchaeota, crenarchaeota.
How many archaea super phyla are there and what are they?
4 called euryarchaeota, TACK, DPANN, Asgard
What allows archaea to live in extreme environments?
Diversity and abundance. They are in soil, freshwater and marine habitats.
What are thermoacidophiles?
Notable archaea, grow at more than 70 degrees with a pH as low as 2.
What are extreme halophiles?
Haloarchaea, need high salt conc to prevent them lyse. Present in salt-evaporation ponds. Produce carotenoid pigments, which turn salt evaporation ponds bright red.
What challenges for haloarchaea face?
They need to get over the fact they are strict aerobes and oxygen has low solubility in high salt environments.
How do haloarchaea get over low oxygen availability?
Alternative to aerobic respiration, bacteriorhodopsin is a membrane protein that acts as a light driven proton pump. Absorption of photons by bacteriorhodopsin initiates the transport of protons out of the cell. Resulting in a transmembrane proton gradient. ATP synthase can use the proton gradient to phosphorylate ADP into ATP.
What are methanogens?
Methanogenic archaea, in animals rumens, without methanogens, ruminant wouldn’t be able to obtain energy from grass. Ruminants produce 10-20% of the methane in the earths atmosphere.
What do methanogens do?
Use CO2 for respiration, reducing it to methane.
How do methanogens make natural gas?
Methanogenic archaea are abundant in landfills, methanogenesis takes place 1 year after solid waste is deposited. Methane captured and used as a fuel. Capturing gases avoids green house emissions and reduces the use of fossil fuels.
