BIOLOGY 2EE3 Lecture Notes - Lecture 4: Biogeochemical Cycle, Dna Supercoil, Gc-Content
23 Jun 2018
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Chapter 4 – Archaea
Achaea look like bacteria but phylogenetic (rRNA gene sequence) analyses show them to be different.
Most grow in extreme conditions
Example: Halobacterium Salinarium – 3-5 M NaCl, Dead Sea, salted foods.
Properties of Archaea:
Size: 0.5–5 μm in diameter.
Shapes vary
oMost - rods, spheres, spirals, some are irregular and some have rectangular shapes
Possess singular, circular chromosomes & lack a membrane-bound nucleus (like Bacteria)
Archaeal DNA is complexed with histones (like Eukaryotes)
oHistones form structures that DNA wraps around
oEukaryal nucleosome – 160 nucleotide-pair DNA around an Octamer of histone proteins
oArchaeal nucleosome – 60 nucleotide-pair DNA around a Tetramere of histone proteins
The Archaea plasma membrane structure is unique to this domain.
Pseudomurein and flagella
oRotate to move the cell
oDifferent from bacteria because they are thinner (10‒14 nm vs. 20‒24 nm)
oUsually composed of two or more different versions of flagellin protein
oLikely growing from BASE rather than from TIP
Cytoskeleton
oCytoskeletal homologues are found in both Bacteria and Archaea.
oTa0583 is an actin homolog in Thermoplasma acidophilum that resembles eukaryal actin.
oCytoskeletal proteins from Methanothermobacter thermoautotrophicum and Methanopyrus kandleri
more closely resemble bacterial cytoskeletal proteins.
Cell envelope (different from Bacteria and Eukarya)
oAll Archaea possess a plasma membrane and most have a cell wall.
1) Plasma membrane
oBacteria & Eukaryote – Fatty acids are linked to glycerol 3-phosphate via an ester linkage
oArchaea - the carbon chains Phentanyl via an Ether linkage
2) Cell wall
oFunction - provides physical and osmotic protection
oArchaea – Pseudomurein (NAG + NAM and L amino acids)
oBacteria – Peptidoglycan in cell wall (NAG + NAM and D amino acid)
Will the cell wall composition of archaea affect sensitivity to Lysozyme or Penicillins?
The cell surface: Archaea flagella
Some archaea possess flagella.
Similar to bacteria in that they rotate to move the cell
Different from bacteria because they are thinner (10‒14 nm vs. 20‒24 nm)
Usually composed of two or more different versions of flagellin protein
Likely growing from BASE rather than from TIP
Major groups of archaea
Most archaeons - Euryarchaeota or Crenarchaeota phylum.
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Document Summary
Achaea look like bacteria but phylogenetic (rrna gene sequence) analyses show them to be different. Example: halobacterium salinarium 3-5 m nacl, dead sea, salted foods. Shapes vary: most - rods, spheres, spirals, some are irregular and some have rectangular shapes. Possess singular, circular chromosomes & lack a membrane-bound nucleus (like bacteria) The archaea plasma membrane structure is unique to this domain. Cytoskeleton: cytoskeletal homologues are found in both bacteria and archaea, ta0583 is an actin homolog in thermoplasma acidophilum that resembles eukaryal actin, cytoskeletal proteins from methanothermobacter thermoautotrophicum and methanopyrus kandleri more closely resemble bacterial cytoskeletal proteins. Similar to bacteria in that they rotate to move the cell. Different from bacteria because they are thinner (10 14 nm vs. 20 24 nm) Usually composed of two or more different versions of flagellin protein. Likely growing from base rather than from tip. Most archaeons - euryarchaeota or crenarchaeota phylum. Sulfolobus viruses are temperate or permanent lysogens: adaptations for survival:
