Download Lecture 19. Proterozoic Earth, Rise in Oxygen, Microbial

The Archaeal Domain
Methanogens and the C Cycle
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
Thermophilic species H2 and CO2 to make CH4.
Methanocaldococcus jannaschii - 85˚C
Methanopyrus kandleri - 100˚C
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)
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
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
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.
.
Halobacterium, Haloferax, Natronobacterium
Late branches in Euryarchaeota.
Aerobic organotrophs.
Halo- in neutral pH environments.
Nat- in alkaline environments.
Halobacterium
Halogeometricum
Haloarcula
Natronococcus
Crenarchaeota
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Sulfolobus:
S-rich acidic hot springs
thermoacidophile
aerobic chemotroph
oxidizes H2S or S˚ to H2SO4
Sulfur Caldron
Crenarchaeota, cont.
Thermoproteus:
long thin rods
strict anaerobes
S˚ reducer (likely an ancient metabolism)
Submarine Vent Crenarchaeota
Pyrodictium (“fire net”):
Topt 105˚C
network of fibers attach to other cells
strict anaerobe
chemolithotroph or chemoorganotroph
Pyrolobus (“fire lobe”):
Topt 106˚C
holds the upper temperature record (species can grow > 113˚C)
walls of black smoker chimney
chemoautotroph
Summary
Euryarchaeota:
methanogens
Archaeoglobus
thermoacidophiles - sulfur respiration
halophiles
Crenarchaeota
many hyperthermophiles
many organotrophs
sulfur respiration
acidophiles and neutrophiles
Lecture 20. Proterozoic Earth and the Rise in
Oxygen
reading: Chapter 4
Hadean
oldest rocks
on Earth - end of
heavy bombardment
origin of the
solar system
Hadean
billions of
years ago:
4.56
rise in
oxygen first multiplate
tectonics?
cellular fossils
Archean
3.8
Proterozoic
2.5
Heavy bombardment.
Delivery of volatiles.
Possible early oceans.
Warm early Earth but a faint young Sun.
Few rocks.
Cambrian
Explosion
Phanerozoic
0.55
present
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.
Proterozoic
origin of the
solar system
oldest rocks
on Earth - end of
heavy bombardment
Hadean
billions of
years ago:
4.56
rise in
oxygen first multiplate
tectonics?
cellular fossils
Archean
3.8
Split into 3 eras:
Paleoproterozoic
Mesoproterozoic
Neoproterozoic
Proterozoic
2.5
3.8/3.5-1.6 Ga
1.6-0.9 Ga
900-543 Ma
Cambrian
Explosion
Phanerozoic
0.55
present
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 Ga
disruptions in carbon isotopes
1.8 Ga
banded iron formation disappears
Sulfur Isotopes
microbes prefer light isotope of sulfur 32S over 33S & 34S
sulfate reducers: 2”CH2O” + SO422H2S
+
Fe2+
----->
FeS2
---> 2HCO3- + H2S
+
2H2
pyrite in sedimentary rocks records presence of sulfate reducers
<--- sediments enriched
in 34S
<--- sediments enriched
in 32S
Stepwise Oxygenation of the Earth
Stage I:
Before 2.32 Ga
O2 < 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:
O2 rises to levels similar to what is seen today.
Oceans no longer stratified - similar to today.
Global Glaciations
Evidence of:
massive glaciers
worldwide
near the equator
~2.3 Ga
Disruptions in the Carbon Isotopes
Disruptions in the Carbon Isotopes, cont.
“Odd” carbon isotopes
recorded in:
organic material - highly
enriched in 12C
and in carbonate rocks highly enriched in 13C
Don’t know the cause.
Global disruption in the carbon cycle?
Disappearance of BIF
Lots of BIF deposited in the Paleoproterozoic.
But by 1.8 Ga it disappears!
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Oceans sediments no longer
contain iron oxides, but contain
iron sulfides (like pyrite) increasing S content of the
oceans.
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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
Lecture 21. Basic Architecture of the Eukaryotic
Cell, Symbioses, Early Eukaryote Fossils.
reading: Chapter 5