Achaea
description
Transcript of Achaea
CrenarchaeotaThe name Crenarchaeota means “scalloped
archaea.”- Are often irregular in shape
All crenarchaeotes synthesize a distinctive tetraether lipid, called crenarchaeol.
Figure 19.6
Crenarchaeota• Desulfurococcales• - Lack cell walls, but have elaborate S-layer• - Reduce sulfur at higher temperatures
Figure 19.8
Desulforococcus mobilis- Hot springs
Ignicoccus islandicus- Marine
organism
CrenarchaeotaBarophilic
hyperthermophiles- Grow near hydrothermal vents on the ocean floor- A common feature is the black smoker.
- Crenarchaeotes that are vent-adapted: - Pyrodictium abyssi- Pyrodictium occultum
Figure 19.9
CrenarchaeotaSulfolobales
- Include species that respire by oxidizing sulfur (instead of reducing it)- Found within hot springs
Figure 19.13
- Sulfolobus solfataricus- A “double extremophile”- Grows at 80oC and pH 3- Oxidizes H2S to sulfuric acid
Crenarchaeota• The crenarchaeote
Cenarchaeum symbiosum inhabits the sponge Axinella mexicana.
• - The relationship is unclear, but they can be co-cultured in an aquarium for many years.
Figure 19.17
Euryarchaeota: MethanogensEuryarchaeota means “broad-ranging archaea.”Are dominated by methanogens
- All are poisoned by molecular oxygen and therefore require complete anaerobiosis.- Major substrates and reactions include:
Carbon dioxide: CO2 + 4H2 → CH4 + 2H2OAcetic acid: CH3COOH → CH4 + CO2
Methanol: 4CH3OH → 3CH4 + CO2 + 2H2OMethylamine: 4CH3NH2 + 2H2O →
3CH4 + CO2 + 4NH3
Methanogens grow in:- Anaerobic soil of wetlands
- Especially rice paddies- Landfills- Digestive tracts of animals
- Termites- Cattle - Humans
- Marine benthic sediments
Anaerobic Habitats for Methanogens
Figure 19.22A
Figure 19.22B
Biochemical pathways of methanogens involve unique cofactors.- These transfer the hydrogens and increasingly reduced carbon to each enzyme in the pathway.
Biochemistry of Methanogenesis
Figure 19.25
The process fixes CO2 onto the cofactor methanofuran (MFR).- The carbon is then passed stepwise from one cofactor to the next, each time losing an oxygen to form water, or gaining a hydrogen carried by another cofactor.
Biochemistry of Methanogenesis
Figure 19.26
Euryarchaeota: HalophilesMain inhabitants of high-salt environments are
members of the class Haloarchaea.
- Their photopigments color salterns, which are used for salt production.- Most are colored red by bacterioruberin, which protects them from light.
Halophilic archaea require at least 1.5M NaCl. Figure 19.29B
Figure 19.28
• Animation: Light-Driven Ion Pumps and Sensors
Click box to launch animation
Retinal-Based Photoheterotrophy
Nanoarchaeota
- Is an obligate symbiont of the crenarchaeote Ignicoccus hospitalis- Host and symbiont genomes have been sequenced, revealing extensive coevolution.
Figure 19.36
Nanoarchaeum equitans
The smallest known euryarchaeotes.