19 1 Phylogenetic and Metabolic Diversity of Archaea

19. 1 Phylogenetic and Metabolic Diversity of Archaea • Archaea share many characteristics with both Bacteria and Eukarya • Archaea are split into two major groups (Figure 19. 1) – Crenarchaeota – Euryarchaeota © 2012 Pearson Education, Inc.

19. 1 Phylogenetic and Metabolic Diversity of Archaea • Bioenergetics and intermediary metabolism of Archaea are similar to those found in Bacteria – Except some Archaea use methanogenesis – Autotrophy via several different pathways is widespread in Archaea © 2012 Pearson Education, Inc.

Figure 19. 1 Marine Euryarchaeota Halobacterium Halococcus Extreme halophiles Marine Crenarchaeota Euryarchaeota Archaeoglobus Natronococcus Methanobacterium Methanocaldococcus Crenarchaeota Halophilic methanogen Methanothermus Sulfolobus Pyrodictium Thermococcus/ Pyrococcus Methanosarcina Nanoarchaeum Methanospirillum Thermoplasma Hyperthermophiles Methanopyrus Picrophilus Ferroplasma Extreme acidophiles © 2012 Pearson Education, Inc. Thermoproteus Desulfurococcus

II. Euryarchaeota • Euryarchaeota – Physiologically diverse group of Archaea – Many inhabit extreme environments • Examples: high temperature, high salt, high acid © 2012 Pearson Education, Inc.

19. 2 Extremely Halophilic Archaea • Haloarchaea • Key genera: Halobacterium, Haloferax, Natronobacterium – Extremely halophilic Archaea – Have a requirement for high salt concentrations • Typically require at least 1. 5 M (~9%) Na. Cl for growth – Found in artificial saline habitats (e. g. , salted foods), solar salt evaporation ponds, and salt lakes (Figure 19. 2) © 2012 Pearson Education, Inc.

Figure 19. 2 © 2012 Pearson Education, Inc.

19. 2 Extremely Halophilic Archaea • Haloarchaea – – – Reproduce by binary fission Do not form resting stages or spores Most are nonmotile Most are obligate aerobes Possess adaptations to life in highly ionic environments • Cell wall is composed of glycoprotein and stabilized by Na+ (Figure 19. 3) © 2012 Pearson Education, Inc.

19. 2 Extremely Halophilic Archaea • Water Balance in Extreme Halophiles – Halophiles need to maintain osmotic balance • This is usually achieved by accumulation or synthesis of compatible solutes – Halobacterium species instead pump large amounts of K+ into the cell from the environment • Intracellular K+ concentration exceeds extracellular Na+ concentration and positive water balance is maintained © 2012 Pearson Education, Inc.

19. 2 Extremely Halophilic Archaea • Proteins of halophiles – Are highly acidic – Contain fewer hydrophobic amino acids and lysine residues © 2012 Pearson Education, Inc.

19. 2 Extremely Halophilic Archaea • Some haloarchaea are capable of light-driven synthesis of ATP (Figure 19. 4) – Bacteriorhodopsin • Cytoplasmic membrane proteins that can absorb light energy and pump protons across the membrane Animation: Bacteriorhodopsin and Light Mediated ATP Synthesis © 2012 Pearson Education, Inc.

Figure 19. 4 In Out Membrane Bacteriorhodopsin ATPase © 2012 Pearson Education, Inc.

19. 3 Methanogenic Archaea • Methanogens (Figure 19. 5) – Key genera: Methanobacterium, Methanocaldococcus, Methanosarcina • Microbes that produce CH 4 • Found in many diverse environments • Taxonomy based on phenotypic and phylogenetic features • Process of methanogenesis first demonstrated over 200 years ago by Alessandro Volta © 2012 Pearson Education, Inc.

Figure 19. 5 © 2012 Pearson Education, Inc.

19. 3 Methanogenic Archaea • Diversity of Methanogens – Demonstrate diversity of cell wall chemistries (Figure 19. 6 and Figure 19. 7) • Pseudomurein (e. g. , Methanobacterium) • Methanochondroitin (e. g. , Methanosarcina) • Protein or glycoprotein (e. g. , Methanocaldococcus) • S-layers (e. g. , Methanospirillum) © 2012 Pearson Education, Inc.

Figure 19. 6 © 2012 Pearson Education, Inc.

Figure 19. 7 © 2012 Pearson Education, Inc.

19. 5 Thermococcales and Methanopyrus • Three phylogenetically related genera of hyperthermophilic Euryarchaeota: – Thermococcus – Pyrococcus – Methanopyrus • Comprise a branch near root of archaeal tree © 2012 Pearson Education, Inc.

19. 5 Thermococcales and Methanopyrus • Thermococcales – Distinct order that contains Thermococcus and Pyrococcus (Figure 19. 11) – Indigenous to anoxic thermal waters – Highly motile © 2012 Pearson Education, Inc.

Figure 19. 11 © 2012 Pearson Education, Inc.

Figure 19. 16 © 2012 Pearson Education, Inc.