1. The Archaeal Domain

2. Estimated global production of methane 10 9 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

3. Methanogens Methanocaldococcus jannaschii - 85˚C Methanopyrus kandleri - 100˚C Thermophilic species H 2 and CO 2 to make CH 4. 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 methane from simple organic compounds (formate, acetate, methanol, methylamines)

4. Euryarchaeota Thermoplasma: thermoacidophile aerobic or anaerobic sulfur respiration found in acidic soils and coal refuse piles Picrophilus: related to Thermoplasma grows optimally at pH 0.6 (can grow at pH -0.06!) membranes leak at pH 4 solfataras

5. Early branching hydrothermal Vent Euryarchaeota. Thermococcus (“hot ball”, growing at 70-95˚C): spherical, highly motile anaerobic chemoorganotroph Pyrococcus (“fire ball”, growing at 70-106˚C): close relative of Thermococcus Thermococcus celer Pyrococcus furiosus

6. Archaeoglobus. Hyperthermophilic sulfate reducer. Hot marine sediments and hydrothermal vents. Shared many unique traits with methanogens: weird enzymes Cultures produce small amounts of methane. Closely related to methanogens. Sulfate reduction genes from the bacterial domain via lateral gene transfer.

7. Halobacterium, Haloferax, Natronobacterium Haloarcula Late branches in Euryarchaeota. Aerobic organotrophs. Halo- in neutral pH environments. Nat- in alkaline environments. Halogeometricum Halobacterium Natronococcus

8. Crenarchaeota Sulfolobus: S-rich acidic hot springs thermoacidophile aerobic chemotroph oxidizes H 2 S or S˚ to H 2 SO 4 Sulfur Caldron

9. Crenarchaeota, cont. Thermoproteus: long thin rods strict anaerobes S˚ reducer (likely an ancient metabolism)

10. Submarine Vent Crenarchaeota Pyrodictium (“fire net”): T opt 105˚C network of fibers attach to other cells strict anaerobe chemolithotroph or chemoorganotroph Pyrolobus (“fire lobe”): T opt 106˚C holds the upper temperature record (species can grow > 113˚C) walls of black smoker chimney chemoautotroph

11. Summary Euryarchaeota: methanogens Archaeoglobus thermoacidophiles - sulfur respiration halophiles Crenarchaeota many hyperthermophiles many organotrophs sulfur respiration acidophiles and neutrophiles

12. Lecture 20. Proterozoic Earth and the Rise in Oxygen reading: Chapter 4

13. Hadean Archean Proterozoic Phanerozoic 4.56 3.8 2.5 0.55 present billions of years ago: origin of the solar system oldest rocks on Earth - end of heavy bombardment rise in oxygen first multi- cellular fossils Cambrian Explosion plate tectonics? Heavy bombardment. Delivery of volatiles. Possible early oceans. Warm early Earth but a faint young Sun. Few rocks.

14. Archean 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.

15. HadeanArchean Proterozoic Phanerozoic 4.56 3.8 2.5 0.55 present billions of years ago: origin of the solar system oldest rocks on Earth - end of heavy bombardment rise in oxygen first multi- cellular fossils Cambrian Explosion plate tectonics? Proterozoic Split into 3 eras: Paleoproterozoic3.8/3.5-1.6 Ga Mesoproterozoic1.6-0.9 Ga Neoproterozoic900-543 Ma

16. Paleoproterozoic, 2.8-1.6 Ga A Time of Fundamental Transitions: 2.4 Ga sulfur isotopic signatures of sulfate reducing bacteria appear 2.32 Ga oxygenation of the atmosphere 2.3 Ga global glaciations 2.2-2.1 Gadisruptions in carbon isotopes 1.8 Ga banded iron formation disappears

17. Sulfur Isotopes microbes prefer light isotope of sulfur 32 S over 33 S & 34 S sulfate reducers: 2”CH 2 O” + SO 4 2- ---> 2HCO 3 - + H 2 S 2H 2 S + Fe 2+ -----> FeS 2 + 2H 2 pyrite in sedimentary rocks records presence of sulfate reducers <--- sediments enriched in 32 S <--- sediments enriched in 34 S

18. Stepwise Oxygenation of the Earth Stage I: Before 2.32 Ga O 2 < 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 Ga Intermediate levels of oxygen. Oceans still stratified. Carbonates and oxides on the surface, iron rich at depth. Stage 3 : O 2 rises to levels similar to what is seen today. Oceans no longer stratified - similar to today.

19. Evidence of : massive glaciers worldwide near the equator ~2.3 Ga Global Glaciations

20. Disruptions in the Carbon Isotopes

21. Disruptions in the Carbon Isotopes, cont. “Odd” carbon isotopes recorded in: organic material - highly enriched in 12 C and in carbonate rocks - highly enriched in 13 C Don’t know the cause. Global disruption in the carbon cycle?

22. Lots of BIF deposited in the Paleoproterozoic. But by 1.8 Ga it disappears! Disappearance of BIF Oceans sediments no longer contain iron oxides, but contain iron sulfides (like pyrite) - increasing S content of the oceans.

23. Appearance of Familiar Microbial Fossils Large diameter microfossils thought to be cyanobacteria appear at ~2.15 Ga. By 1.8 Ga, fossil akinetes - produced by one group of cyanobacteria are seen. this image is copyrighted by the Precambrian Paleobiology Research Group - UCLA

24. Lecture 21. Basic Architecture of the Eukaryotic Cell, Symbioses, Early Eukaryote Fossils. reading: Chapter 5