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Estimated global production of methane 109 tons/yr.A cow can produce 100 liters of methane a day.Methane is an important greenhouse gas.Methanogens are found in many places in the Euryarchaeota.
Methanogens and the C Cycle
Methanogens
Methanocaldococcus jannaschii - 85˚C
Methanopyrus kandleri - 100˚C
Thermophilic species H2 and CO2 to make CH4.
Methanopyrus:-isolated from sediments near submarine
hydrothermal vent chimney-generation time is 1hr at 100˚C-branches at the base of the archaeal tree
Mesophilic species can also make methanefrom simple organic compounds (formate,acetate, methanol, methylamines)
Euryarchaeota
Thermoplasma:thermoacidophileaerobic or anaerobic sulfur respirationfound in acidic soils and coal refuse piles
Picrophilus:related to Thermoplasmagrows optimally at pH 0.6(can grow at pH -0.06!)membranes leak at pH 4solfataras
Early branching hydrothermal Vent Euryarchaeota.
Thermococcus (“hot ball”, growing at 70-95˚C):spherical, highly motileanaerobic chemoorganotroph
Pyrococcus (“fire ball”, growing at 70-106˚C):close relative of Thermococcus Thermococcus celer
Pyrococcus furiosus
Archaeoglobus
.
Hyperthermophilic sulfate reducer.Hot marine sediments and hydrothermal vents.Shared many unique traits with methanogens: weird enzymesCultures produce small amounts of methane.Closely related to methanogens.Sulfate reduction genes from the bacterial domain via lateral gene transfer.
Halobacterium, Haloferax, Natronobacterium
Haloarcula
Late branches in Euryarchaeota.Aerobic organotrophs.Halo- in neutral pH environments.Nat- in alkaline environments.
Halogeometricum
Halobacterium
Natronococcus
Crenarchaeota
Sulfolobus:S-rich acidic hot springsthermoacidophileaerobic chemotrophoxidizes H2S or S˚ to H2SO4
QuickTime™ and aTIFF (Uncompressed) decompressor
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Sulfur Caldron
Crenarchaeota, cont.
Thermoproteus:long thin rodsstrict anaerobesS˚ reducer (likely an ancient metabolism)
Submarine Vent Crenarchaeota
Pyrodictium (“fire net”):Topt 105˚Cnetwork of fibers attach to other cellsstrict anaerobechemolithotroph or chemoorganotroph
Pyrolobus (“fire lobe”):Topt 106˚Cholds the upper temperature record (species can grow > 113˚C)walls of black smoker chimneychemoautotroph
Summary
Euryarchaeota:methanogensArchaeoglobusthermoacidophiles - sulfur respirationhalophiles
Crenarchaeotamany hyperthermophilesmany organotrophssulfur respirationacidophiles and neutrophiles
Hadean
Hadean Archean Proterozoic Phanerozoic
4.56 3.8 2.5 0.55 presentbillions of years ago:
origin of thesolar system
oldest rockson Earth - end ofheavy bombardment
rise inoxygen first multi-
cellular fossilsCambrianExplosion
platetectonics?
Heavy bombardment.Delivery of volatiles.Possible early oceans.Warm early Earth but a faint young Sun.Few rocks.
Archean
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Stromatolites and banded iron formation, particularly at end of Archean.Greenstone belts giving rise to continents.Creation of continental shields.Great carbonate reefs.Beginnings of life.
Hadean Archean Proterozoic Phanerozoic
4.56 3.8 2.5 0.55 presentbillions of years ago:
origin of thesolar system
oldest rockson Earth - end ofheavy bombardment
rise inoxygen first multi-
cellular fossilsCambrianExplosion
platetectonics?
Proterozoic
Split into 3 eras:Paleoproterozoic 3.8/3.5-1.6 GaMesoproterozoic 1.6-0.9 GaNeoproterozoic 900-543 Ma
Paleoproterozoic, 2.8-1.6 Ga
A Time of Fundamental Transitions:2.4 Ga sulfur isotopic signatures of sulfate reducing
bacteria appear2.32 Ga oxygenation of the atmosphere2.3 Ga global glaciations2.2-2.1 Ga disruptions in carbon isotopes1.8 Ga banded iron formation disappears
Sulfur Isotopesmicrobes prefer light isotope of sulfur 32S over 33S & 34S
sulfate reducers: 2”CH2O” + SO42- ---> 2HCO3
- + H2S
2H2S + Fe2+ -----> FeS2 + 2H2
pyrite in sedimentary rocks records presence of sulfate reducers
<--- sediments enriched in 32S
<--- sediments enriched in 34S
Stepwise Oxygenation of the Earth
Stage I:Before 2.32 GaO2 < 10-5 present atmospheric levels (PAL)Very low levels of oxygen.Stratified oceans.Carbonates on the surface, iron rich at depth.
Stage 2:Transition period 2.32 - 1.8 GaIntermediate levels of oxygen.Oceans still stratified.Carbonates and oxides on the surface, iron rich at depth.
Stage 3:O2 rises to levels similar to what is seen today.Oceans no longer stratified - similar to today.
Disruptions in the Carbon Isotopes, cont.
“Odd” carbon isotopesrecorded in:
organic material - highlyenriched in 12C
and in carbonate rocks -highly enriched in 13C
Don’t know the cause.Global disruption in the carbon cycle?
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Lots of BIF deposited in the Paleoproterozoic.But by 1.8 Ga it disappears!
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Disappearance of BIFOceans sediments no longercontain iron oxides, but containiron sulfides (like pyrite) - increasing S content of theoceans.
Appearance of Familiar Microbial Fossils
Large diameter microfossils thought to be cyanobacteria appear at ~2.15 Ga.
By 1.8 Ga, fossil akinetes - producedby one group of cyanobacteria are seen.
this image is copyrighted by the Precambrian PaleobiologyResearch Group - UCLA