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Archaea
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!
+ -
Pseudomurein(Murein = NAG-NAM of peptidoglycan in Bacteria)
* Insensitive to penicillin.* NAM replaced by NAT* Unique side-chain peptide cross-links.
Lipid Differences:
* Hydrocarbons not fatty acids
* Ether linked to glycerol not ester linked
Two leaves (bilayer) of C20 diethers
Single layer of rigid C40 tetraethers
Which is most likely that for an extreme thermophile?
Unique Means of
Autotrophy* No Calvin Cycle
* Reversed Modified TCA Cycle
* Reductive Acetyl-CoA
Methanogens
MethanogensObligate anaerobes dependent on fermentation bacteria.
Chemoheterotrophic: AcetoclasticAcetate to CO2 and methane
Chemoautotrophic: H2 or formate as energy & electron sourceCO2 to methane and other cellular
components
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.
Methanogen Habitats
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
Anearobic Complex Organic
Matter Degradation
1) Hydrolysis
2) Fermentation
3) Acetogenesis
4) Sulfate Reduction
5) Methanogenesis
Carbon Cycle
Methylotrophy
Methane Production - Consumption
Subsurface Methane Production:
Methanogens (shallower)(12C reacts faster than 13C)
Geothermal (deeper)
Sewage Treatment Plants
Global ImportancePotent 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)