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PowerPoint® Lecture Presentations CHAPTER 17 Diversity of Archaea © 2018 Pearson Education, Inc. 2 © 2018 Pearson Education, Inc. Archaea comes from the Greek word meaning “ancient.” An appropriate name, because many archaea thrive in conditions mimicking those found more than 3.5 billion ye...
PowerPoint® Lecture Presentations CHAPTER 17 Diversity of Archaea © 2018 Pearson Education, Inc. 2 © 2018 Pearson Education, Inc. Archaea comes from the Greek word meaning “ancient.” An appropriate name, because many archaea thrive in conditions mimicking those found more than 3.5 billion years ago. http://w ww.yout ube.com /watch? v=0W-u Itr5M4g 3 © 2018 Pearson Education, Inc. 4 © 2018 Pearson Education, Inc. 5 © 2018 Pearson Education, Inc. Diversity of Archaea • Archaea share many characteristics with both Bacteria and Eukarya. • common traits of all Archaea • ether-linked lipids • a lack of peptidoglycan in cell walls • structurally complex RNA polymerases similar to those of Eukarya © 2018 Pearson Education, Inc. Diversity of Archaea • Hallmark traits of Archaea • only domain that makes methane (methanogenesis) • Many Archeans live in extreme environments (extremophiles). • Archaea are split into five major groups. (Figure 17.1) • • • • • Euryarchaeota Crenarchaeota Thaumarchaeota Korarchaeota Nanoarchaeota © 2018 Pearson Education, Inc. Haloarchaea Methanogens Lack cell walls Thermoplasmatales Hyperthermophiles © 2018 Pearson Education, Inc. I. Euryarchaeota • Physiologically diverse group of Archaea that include Methanogens • Many inhabit extreme environments. • examples: high temperature, high salt, high acid © 2018 Pearson Education, Inc. 17.1 Extremely Halophilic Archaea • Key genera: Halobacterium, Haloferax, Natronobacterium • Haloarchaea • extremely halophilic Archaea that live in hypersaline environments • have a requirement for high salt concentrations to maintain cell integrity and metabolic processes • typically require at least 1.5 M (~9 percent) NaCl for growth • found in artificial saline habitats (e.g., salted foods), solar salt evaporation ponds, and salt lakes (Figure 17.2) © 2018 Pearson Education, Inc. © 2018 Pearson Education, Inc. Figure 17.2 17.1 Extremely Halophilic Archaea • Haloarchaea • hypersaline environments • Extremely hypersaline environments are rare. • most found in hot, dry areas of world • Salt lakes can vary in ionic composition depending on surrounding topography and geology. • Great Salt Lake similar to concentrated seawater • Soda lakes are highly alkaline hypersaline environments. • Different environments select for different microbes. • Salt lakes can be very productive, with high levels of carbon dioxide fixation from a variety of autotrophic Archaea, Bacteria and Eukarya. © 2018 Pearson Education, Inc. 17.2 Methanogenic Archaea • Methanogens (Figure 17.5) • key genera: Methanobacterium, Methanocaldococcus, Methanosarcina • microbes that produce methane (CH4) • found in many diverse environments, particularly anoxic (oxygen free) environments • taxonomy based on phenotypic and phylogenic features • The ability to produce methane from carbon dioxide likely evolved once in Euryarchaeota and was lost in haloarchaea and Thermoplasmatales. © 2018 Pearson Education, Inc. © 2018 Pearson Education, Inc. Figure 17.5 17.2 Methanogenic Archaea • Diversity of methanogens • Methanocaldococcus jannaschii is a model methanogen. • Central metabolic pathway genes resemble those of Bacteria. • Genetic machinery genes, directing transcription and translation, are more closely aligned with Eukarya. • Forty percent of its genes have no bacterial or eukaryotic counterparts, and not all of these are for producing methane. • Methanogens demonstrate diversity of cell wall chemistries (Figure 17.6, Figure 17.7, and Figure 17.8) • • • • pseudomurein (e.g., Methanobacterium) methanochondroitin (e.g., Methanosarcina) protein or glycoprotein (e.g., Methanocaldococcus) S-layers (e.g., Methanospirillum) © 2018 Pearson Education, Inc. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 16 © 2018 Pearson Education, Inc. © 2018 Pearson Education, Inc. Figure 16.6 17.3 Thermoplasmatales • Key genera: Thermoplasma, Picrophilus, Ferroplasma • Taxonomic order within the Euryarchaeota • Thermophilic and/or extremely acidophilic • Thermoplasma and Ferroplasma lack cell walls and are similar in appearance to mycoplasmas. © 2018 Pearson Education, Inc. 17.3 Thermoplasmatales • Thermoplasma (Figure 17.9) • chemoorganotrophs • facultative aerobes via sulfur respiration • thermophilic • acidophilic • found in self-heating coal piles (Figure 17.10) © 2018 Pearson Education, Inc. © 2018 Pearson Education, Inc. Figure 16.9 17.4 Thermococcales and Methanopyrus Hyperthermophiles • Key genera: Thermococcus, Pyrococcus, Methanopyrus • Three phylogenetically related genera of hyperthermophilic Euryarchaeota • Comprise a branch near root of archaeal tree • Some are hyperthermophiles optimum temp of 100oC. © 2018 Pearson Education, Inc. III. Crenarchaeota • 17.8 Habitats and Energy Metabolism • 17.9 Crenarchaeota from Terrestrial Volcanic Habitats • 17.10 Habitats © 2018 Pearson Education, Inc. Crenarchaeota from Submarine Volcanic 17.8 Habitats and Energy Metabolism • Most cultured representatives are hyperthermophiles. • found in extreme heat environments (Figure 17.18) • Other representatives are found in extreme cold environments. © 2018 Pearson Education, Inc. © 2018 Pearson Education, Inc. © 2018 Pearson Education, Inc. Figure 17.18 © 2018 Pearson Education, Inc. 17.9 Crenarchaeota from Terrestrial Volcanic Habitats • Key genera: Sulfolobus, Acidianus, Thermoproteus, Pyrobaculum • Sulfolobales (Figure 17.19) • Sulfolobus • grows in sulfur-rich acidic hot springs • aerobic chemolithotrophs that oxidize reduced sulfur or iron • Acidianus • also lives in acidic sulfur hot springs • uses elemental sulfur both aerobically and anaerobically © 2018 Pearson Education, Inc. 17.9 Crenarchaeota from Terrestrial Volcanic Habitats • Thermoproteales (Figure 17.20) • Thermoproteus • strict anaerobe that carries out sulfur-based anaerobic respiration • Thermofilum • strict anaerobe that carries out sulfur-based anaerobic respiration • inhabit neutral or slightly acidic hot springs or hydrothermal vents © 2018 Pearson Education, Inc. © 2018 Pearson Education, Inc. Figure 17.20 17.10 Crenarchaeota from Submarine Volcanic Habitats • Key genera: Pyrodictium, Pyrolobus, Ignicoccus, Staphylothermus • Shallow-water thermal springs and deep-sea hydrothermal vents harbor the most thermophilic of all known Archaea. © 2018 Pearson Education, Inc. 17.10 Crenarchaeota from Submarine Volcanic Habitats • Pyrodictium and Pyrolobus (Figure 17.21) • optimum growth temperature above 100°C • Pyrolobus fumarii is one of the most thermophilic. • Strain 121 can grow in temperatures up to 121°C. © 2018 Pearson Education, Inc. 17.10 Crenarchaeota from Submarine Volcanic Habitats • Desulfurococcus and Ignicoccus (Figure 17.22) • Desulfurococcus is a strictly anaerobic S0-reducing organism. • Ignicoccus grows optimally at 90°C, and its metabolism is H2/S0 based. • Ignicoccus contains an outer membrane similar to that of gram-negative Bacteria. © 2018 Pearson Education, Inc. IV. Evolution and Life at High Temperatures • 17.11 An Upper Temperature Limit for Microbial Life • 17.12 Molecular Adaptations to Life at High Temperature • 17.13 Hyperthermophilic Archaea, H2, and Microbial © 2018 Pearson Education, Inc. Evolution 17.11 An Upper Temperature Limit for Microbial Life • What are the upper temperature limits for life? • New species of thermophiles and hyperthermophiles are being discovered. (Figure 17.25) • Laboratory experiments with biomolecules suggest 140–150°C. • The upper limit for survival without growth is likely higher. © 2018 Pearson Education, Inc. © 2018 Pearson Education, Inc. Figure 17.25 17.12 Molecular Adaptations to Life at High Temperature • Protein folding and thermostability • amino acid composition similar to that of nonthermostable proteins • Structural features improve thermostability. • highly hydrophobic cores • increased ionic interactions on protein surfaces © 2018 Pearson Education, Inc. 17.12 Molecular Adaptations to Life at High Temperature • Chaperones • class of proteins that refold partially denatured proteins • Thermosome • major chaperonin protein complex in Pyrodictium (Figure 17.26) © 2018 Pearson Education, Inc. 17.12 Molecular Adaptations to Life at High Temperature • DNA stability • high intracellular solute levels stabilize DNA • reverse DNA gyrase • introduces positive supercoils into DNA • stabilizes DNA • found only in hyperthermophiles • High intracellular levels of polyamines (e.g., putrescine, spermidine) stabilize DNA and RNA. • DNA-binding proteins (histones) compact DNA into nucleosome-like structures. (Figure 17.27) © 2018 Pearson Education, Inc. © 2018 Pearson Education, Inc. Figure 17.27 17.12 Molecular Adaptations to Life at High Temperature • Lipid stability • possess dibiphytanyl tetraether type lipids; form a lipid monolayer membrane structure • SSU rRNA stability • higher GC content © 2018 Pearson Education, Inc. 17.13 Hyperthermophilic Archaea, H2, and Microbial Evolution • Hyperthermophiles may be the closest descendants of ancient microbes. • Hyperthermophilic Archaea and Bacteria are found on the deepest, shortest branches of the phylogenetic tree. • Oxidation of H2 is common to many hyperthermophiles and may have been the first energy-yielding metabolism. (Figure 17.28) © 2018 Pearson Education, Inc. DNA polymerase I from the bacterium Thermus aquaticus, called Taq polymerase, was the first thermostable DNA polymerases utilized in PCR. Archaeal proof-reading polymerases, such as Pwo from Pyrococcus woesei, Pfu from P. furiosus, Deep Vent polymerase from the Pyrococcus strain GB-D and Vent polymerase from Thermococcus litoralis, have an error rate that is up to tenfold 42 lower than that of Taq polymerase. © 2018 Pearson Education, Inc.
