2 Discovery of Archaea Prior to 1977 they were considered bacteria 1977 Carl Woese and George Fox proposed a new domain/kingdomS rRNA and 18S rRNA sequences justify separation2003 genome sequence analysis justifies kingdom/domain status
4 How Many Kingdoms? Extant 8 5 3 2 Extinct 1 Long Time with Multicellular AnimalsMyxozoansProtozoansTracheophytesBryophytesTrue FungiSlime MoldsRed algaeBrown AlgaeGreen AlgaeChrysophytesEuglenoidsArchezoansArchaebacteriaBacteria8532Extinct1Long Time withProkaryotes onlyThe prokaryotes are a?Grade!Original Cell
5 Archaea Ancient origin, but appreciated more recently Somewhat more advanced than BacteriaExtremophiles-90°C pH2 25M anaerobic -4°C Antarctica!MethanogensHalophytesSulfur metabolismDNA binding proteins (but not histones)Unicellular, colonial, filamentousBacillus, coccus, spirillum, plate-like, etc.Size: 0.1 to 15 µm diam. x 200 µm long
7 Prokaryotic Growth Cells are generally very small Cells may double in size but only before binary fissionGrowth mostly in terms of cell number or colony size, etc.Doubling time in cell numbers may be 20 minutes in ideal conditionsCould quickly take over the earth if conditions could remain idealVery competitive in ideal environmentsUltimate survivors billion years!
8 Cell Structure: Boundary Thermoplasmacell membrane bilayerphosphoglycerohydrocarbon, etc.sulfo- or glyco-glycerohydrocarbon(ether link not ester link)transport proteinscytosolregulates input/outputGram PositiveMethanobacteriumGram NegativeThermoproteuscell wall-glycan(no muramic acid)prevents burstingturgor pressurethinsurface layerglycoproteinreleases dye
9 Homeostasis - metabolism Facultative and Obligate Anaerobes and AerobesNutrition ModeEnergy SourceCarbon SourcePhotoautotrophLightCO2ChemoautotrophInorganic chemPhotoheterotrophOrganic chemChemoheterotrophChemoautotroph acetyl-CoA or reverse TCA to fix CO2 Photoautotroph Calvin Cycle (Methanococcus, Pyrococcus)Chemoheterotroph citric acid cycle, fermentationSulfur transporters used to drive ATP synthesis
10 How do Archaea tolerate the heat? Proteins stabilized by more ionic bridges between amino acid r-groups and more-hydrophobic core amino acidsHeat shock protein (chaperonins) refold denatured proteins…Pyrococcus 121°C for 1 hour!DNA depurination reduced by presence of 2,3-diphosphoglycerate.DNA supercoiling by reverse gyrase reduces denaturationSac7d in Sulfobolus is a minor groove protein increases the melting temperature by 40°CHistone-like proteins help stabilize DNA as wellHeat-resistant di-bi-phytanyl diether lipid membranes (monolayer) prevent delamination of membrane
11 Cell Membrane Structure Composed of diglyceridesR group may be phosphate, sulfate, or sugarLong chain branched hydrocarbon (not fatty acid)Hydrocarbons may be C20 or C40If C20, the membrane is a bilayer:ORIf C40, the membrane is a monolayerORIn some species, the membrane is a mixture of both C20 and C40 diglycerides forming a mixed mono-/bi-layer