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 Which is most likely that for an extreme thermophile? Single layer of rigid C40 tetraethers
Unique Means of Autotrophy * No Calvin Cycle * Reversed Modified TCA Cycle * Reductive Acetyl-CoA
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
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.
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 = +820 mV E = +420 mV E = -200 mV E = -240 mV Methanogenesis
Anearobic Complex Organic Matter Degradation • Hydrolysis • Fermentation • Acetogenesis • Sulfate Reduction • Methanogenesis
Carbon Cycle Methylotrophy
Subsurface Methane Production: Methanogens (shallower) (12C reacts faster than 13C) Geothermal (deeper)
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)