1. Archaea

4. Gram Staining Archaea
(Not for the same reasons as Bacteria.)
* Gram+ cell wall like with Gram+ Bacteria, but different
biochemical composition that peptidoglycan.
* Gram–
due to glycoprotein surface layer not an
outer membrane.
* Some with NO cell wall!
+ -

5. Pseudomurein
(Murein = NAG-NAM of
peptidoglycan in Bacteria)
* Insensitive to penicillin.
* NAM replaced by NAT
* Unique side-chain peptide
cross-links.

6. Lipid
Differences:
* Hydrocarbons
not fatty acids
* Ether linked to glycerol
not ester linked

7. Two leaves
(bilayer) of
C20 diethers
Single layer
of rigid C40
tetraethers
Which is most likely that for an extreme thermophile?

8. Unique
Means of
Autotrophy
* No Calvin Cycle
* Reversed Modified
TCA Cycle
* Reductive Acetyl-CoA

9. Methanogens

10. Methanogens
Obligate anaerobes dependent on fermentation bacteria.
Chemoheterotrophic:
Acetoclastic
Acetate to CO2 and methane
Chemoautotrophic:
H2 or formate as energy & electron source
CO2 to methane and other cellular
components

12. Methanogenesis Pathway
MCR protein is a 3
component complex;
Component C is made of 3
polypeptide subunits (α,β,γ)
encoded on mcrA, mcrB,
and mcrG genes.

13. Methanogen Habitats

14. Aerobic respiration yields greatest energy due to very positive
O2 redox potential.
Without O2, anaerobic respiration uses alternate terminal
electron acceptors in the order of decreasing redox potential.
E = -240 mV
Methanogenesis
E = +820 mV
E = +420 mV
E = -200 mV

15. Anearobic
Complex Organic
Matter Degradation
1) Hydrolysis
2) Fermentation
3) Acetogenesis
4) Sulfate Reduction
5) Methanogenesis

16. Carbon Cycle
Methylotrophy

17. Methane Production - Consumption

18. Subsurface Methane Production:
Methanogens (shallower)
(12
C reacts faster than 13
C)
Geothermal (deeper)

19. Sewage Treatment Plants

20. Global Importance
Potent Greenhouse Gas
• Over 30x more potent than carbon dioxide.
• Increasing emissions by 1% per year.
• Increased by more nitrogen and carbon dioxide.
• Primary culprits:
– Wetlands (N)
– Termites (N)
– Fossil Fuel (MM)
– Rice paddies (MM)
– Wastes (MM)
– Rumen and Enteric (N/MM)
– Deforestation Burning (MM)