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Achaea

Achaea. Figure 19.2. Figure 19.5. Crenarchaeota. The name Crenarchaeota means “scalloped archaea.” - Are often irregular in shape All crenarchaeotes synthesize a distinctive tetraether lipid, called crenarchaeol . Figure 19.6. Crenarchaeota. Desulfurococcales

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Achaea

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  1. Achaea

  2. Figure 19.2

  3. Figure 19.5

  4. Crenarchaeota The name Crenarchaeota means “scalloped archaea.” - Are often irregular in shape All crenarchaeotes synthesize a distinctive tetraether lipid, called crenarchaeol. Figure 19.6

  5. Crenarchaeota Desulfurococcales - Lack cell walls, but have elaborate S-layer - Reduce sulfur at higher temperatures Desulforococcus mobilis - Hot springs Ignicoccus islandicus - Marine organism Figure 19.8

  6. Crenarchaeota Barophilic 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

  7. Crenarchaeota Sulfolobales - Include species that respire by oxidizing sulfur (instead of reducing it) - Found within hotsprings - Sulfolobus solfataricus - A “double extremophile” - Grows at 80oC and pH 3 - Oxidizes H2S to sulfuric acid Figure 19.13

  8. 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

  9. Euryarchaeota: Methanogens Euryarchaeota 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 + 2H2O Acetic acid: CH3COOH → CH4 + CO2 Methanol: 4CH3OH → 3CH4 + CO2 + 2H2O Methylamine: 4CH3NH2 + 2H2O → 3CH4 + CO2 + 4NH3

  10. Anaerobic Habitats for Methanogens Methanogens grow in: - Anaerobic soil of wetlands - Especially rice paddies - Landfills - Digestive tracts of animals - Termites - Cattle - Humans - Marine benthic sediments Figure 19.22A Figure 19.22B

  11. Biochemistry of Methanogenesis Biochemical pathways of methanogens involve unique cofactors. - These transfer the hydrogens and increasingly reduced carbon to each enzyme in the pathway. Figure 19.25

  12. Biochemistry of Methanogenesis 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. Figure 19.26

  13. Great Salt Lake

  14. Euryarchaeota: Halophiles Main inhabitants of high-salt environments are members of the class Haloarchaea. Figure 19.28 - 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

  15. Figure 19.31

  16. Animation: Light-Driven Ion Pumps and Sensors Retinal-Based Photoheterotrophy Click box to launch animation

  17. Halophilic prokaryotes

  18. Halobacterium selinarum

  19. H. salinarum glycoprotein cell wall

  20. Nanoarchaeota The smallest known euryarchaeotes. Nanoarchaeum equitans - Is an obligate symbiont of the crenarchaeote Ignicoccus hospitalis - Host and symbiont genomes have been sequenced, revealing extensive coevolution. Figure 19.36

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