The Archaeal Domain

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

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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

Lecture 20. Proterozoic Earth and the Rise in Oxygen

reading: Chapter 4

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.

Evidence of:massive glaciersworldwidenear the equator~2.3 Ga

Global Glaciations

Disruptions in the Carbon Isotopes

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

Lecture 21. Basic Architecture of the Eukaryotic Cell, Symbioses, Early

Eukaryote Fossils.

reading: Chapter 5