19.1 Phylogenetic and Metabolic Diversity of Archaea 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
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%) NaCl 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 CH4 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.
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