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Category: Microbial Genetics and Molecular Biology; Environmental Microbiology

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Figure 5 (Chapter 23)
Uptake of fluorescent archaeosomes by phagocytic cells. Archaeosomes composed of total polar lipids were prepared either by incorporating a small amount of the fluorescent lipid rhodamine-phosphatidylethanolamine (62) or by entrapping 1.5 mM carboxyfluorescein (66). Uptake was performed in 1 ml of RPMI medium added to 0.5 million adhered cells (62). Panels show 30-min uptakes: (A) M. smithii rhodamine-archaeosomes (100 μg) by thioglycollate-activated mouse peritoneal macro-phages; (B) uptake of M. smithii rhodamine-archaeosomes (25 μg) by bone marrow-derived DCs; (C) uptake of M. mazei carboxy-fluorescein-archaeosomes (40 μg) by macrophages culture J774A.1; and (D) uptake of H. salinarum rhodamine-archaeosomes (100 μg) by thioglycollate-activated mouse peritoneal macrophages.

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Figure 7 (Chapter 2)
The euryarchaeon SM1 and its extracellular appendages (“hami”). (A) Electron micrograph of a “hamus.” (B) Enlargement of the hook region. (C) Simplified model of a hamus with the three filaments shown in different colors and 3D reconstruction from cryoelectron microscopy. (D) “String of pearls,” archaeal/bacterial community in cold, sulfurous spring water. (E) Hamus model with dimensions. (F) Natural biofilm hybridized with an SM1-specific fluorescent probe; circle diameter, 4 μm. (G) Pt-shadowed electron micrograph of a single SM1 cell with appendages. Figure compiled, modified, and reproduced from Biospektrum (264) and Molecular Microbiology (265) with permission of the publishers.

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Figure 8 (Chapter 2)
Three-dimensional structures of archaeal Argonaute proteins. (A) 3D structure of P. furiosus Ago with the PAZ domain (blue) and the PIWI domain (green/yellow) (PDB code 1U04). (B, C) Similarity of the P. furiosus PIWI domain (B) with the catalytic core of the E. coli RNase H1 (C) (PDB code 1RDD) with the catalytic DDE triad and bound Mg2+ ion highlighted. The P. furiosus PIWI domain has a putative, similar catalytic DDE triad and a conserved Arg (position 627). (D, E) 3D structure of the P. furiosus PAZ domain (D) and comparison with the homologous domain of human Ago1 bound to an siRNA mimic (E) (PDB code 1SI3). (F) Domain structures of Ago proteins, including N-terminal, linker (L1 and L2), PAZ, Mid, and PIWI domains and of human dicer comprising a DEXH helicase, a PAZ, two RNase III, and dsRBD domains and a conserved domain of unknown function (DUF). Panels A to E reproduced with modifications from Current Opinion in Structural Biology (241) with permission of the publisher.

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Figure 10 (Chapter 2)
Three-dimensional structure of the 50S subunit of the Haloarcula marismortui ribosome. The ribo-some arm around ribosomal protein L1 was omitted (for a more complete picture see reference 200). Figure drawn from the coordinates from PDB entry 1QVF (200); ribosomal RNAs are displayed in red (backbone) and gray (bases), proteins are displayed as yellow backbone ribbons. Top left, crown view; top right, back view; bottom, bottom view; the circle indicates the position of the polypeptide exit tunnel.

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Figure 11 (Chapter 2)
Haloarchaea in liquid cultures and within salt crystals. (A) Cultures of Haloferax and Halorubrum: first flask (front), H. volcanii WFD11 wild type; second flask, H. volcanii WFD11 gas vesicle ΔD mutant (see Fig. 14); third flask, H. volcanii WFD11 gas vesicle ΔD mutant complemented with the gvpD gene; fourth flask, Halorubrum vacuolatum wild type. (B) Himalayan rock salt (“Eubiona”; Claus, GmbH, Baden-Baden, Germany). (C, D) Crystals formed from dried Halobacterium cultures (cells trapped within). Bars, 1 cm. Crystals courtesy of F. Pfeifer, Darmstadt, Germany. Photographs by F. Pfeifer, Darmstadt, Germany (panel A), and A. Kletzin (panels B to D).

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Figure 15 (Chapter 2)
Solfatara and Pisciarelli fumaroles. (Left) Fumaroles in the Solfatara caldera (Pozzuoli near Naples, Italy) with deposition of sulfur, mercury, and arsenic salts. (Right) Fumarole-heated hole with boiling water, typical of habitats for Sulfolobales (Pisciarelli, near Naples, Italy). Photos taken by A. Kletzin.

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Figure 18 (Chapter 2)
Three-dimensional structures of tungsten-containing aldehyde:ferredoxin oxidoreductases from Pyrococcus furiosus. (A) Cartoon of the formaldehyde:ferredoxin oxidoreductase (FOR), homotetrameric holoenzyme (150). (B) Cartoon of the aldehyde:ferredoxin oxidoreductase (AOR) homodimeric holoenzyme (53). (C) Peptide chains of AOR (cyan) superimposed on FOR (magenta) showing close structural similarity (150). (D) Active-site cavity of the FOR with surrounding residues and glutarate shown (150). (E) [4Fe-4S] cluster and the W-(bis-tungstopterin) cofactor of the AOR (53). FOR images reproduced from the Journal of Molecular Biology with permission of the publisher (150); AOR images reproduced from Science (53) with permission of the publisher.

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Figure 19 (Chapter 2)
Model of the Aeropyrum voltage-gated K+-channel KvAP and comparison with the Streptomyces lividans KcsA K+ channel. (A) Stereo view of the KvAP pore with electron density map contoured at 1.0 Δ_ carbon (yellow), nitrogen (blue), oxygen (red), potassium (green). (B, C) α-Carbon traces of the KvAP pore (blue) and the Streptomyces lividans KcsA K+ channel (green) shown as a side view (B) and end-on from the intracellular side (C); S5, S6, outer and inner helices; glycine-gating hinges (red spheres). (D, E) Models of the closed (D) and open (E) KvAP structures based on the positions of the paddles (red), the pore and the S5 and S6 helices of KcsA. Reproduced with modifications from Nature (168, 169) with permission of the publisher.

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Figure 20 (Chapter 2)
Electron micrograph and fluorescence images of Ignicoccus and Nanoarchaeum. (A) Transmission electron micrograph of thin-sectioned Ignicoccus cell with broad periplasmic space (P) and budded vesicles; OM, outer membrane, C, cytoplasm, bar, 1 μm. (B) Negative stained Ignicoccus outer membrane, highlighting power spectra of image field (C to E) (275). Panels A to E reproduced from Biochemical Society Symposia (275) with permission of the publisher. (F) Ul-trathin section of Nanoarchaeum cells attached to the outer membrane of Ignicoccus sp. KIN/4. (G) Platinum shadowing of Ignicoccus cell with several Nanoarchaeum cells attached (left side of photograph). (H) Confocal laser-scanning micrograph using Nanoarchaeum (red) and Ignicoccus- specificprobes (green). Panels F to H reproduced from Nature (152) with permission of the publisher.

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Figure 23 (Chapter 2)
Three-dimensional structures of the T. acidophilum proteasome and tricorn protease. (A) Side view of the 26S proteasome/activator particle with the two sets of seven terminal PA26 subunits and the two α7β7β7α7 rings (PDB code 1YA7) (93). (B) Top view of the 20S proteasome core particle showing the sevenfold symmetry (PDB code 1PMA) (245). (C) Top view of the homohexameric tricorn protease complexed with a tride-cameric peptide derivative (PDB code 1N6E) (195).

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Figure 27 (Chapter 2)
Three-dimensional structure of the A. ambivalens sulfur oxygenase reductase. (A) The SOR holoenzyme. Cartoon representation viewed along the crystallographic fourfold axis; cyan, α-helices; purple, β-sheets; red spheres, Fe ions. (B) Molecular accessible surface representation in the same orientation of inner surface of the sphere, color-coded according to the calculated electrostatic potentials: red, ≤ — 10 ± 1 KT/e; white, neutral; blue, ≥ + 10 ±1 KT/e. (C) Cavity surface representation of the catalytic pocket, with conserved cysteines and iron highlighted; gray arrow, cavity entrance. (D) Effect of mutants on SOR activity; †, zero activity; ↓ reduced activity; ⇓ strongly reduced activity. The core active site composed of the Fe site and the persulfide-modified Css31 is highlighted within ellipsoids. Reproduced with minor modifications from Science (411) with permission from the publisher.

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Figure 28 (Chapter 2)
Canonical respiratory chain in bacteria and mitochondria. Scheme based on 3D structures with the exception of the membrane domain of complex I, for which a structure is not available. Domains that have not been identified in Archaea are shown in black. PP, periplasm; CM, cytoplasmic membrane; CP, cytoplasm; Q, quinols/quinones. The figure was prepared from the coordinates of PDB entries 1FUG (complex I, Thermus thermophilus), 1NEK (complex II, E. coli), 1KYO (complex III, Saccharomyces cerevisiae), 1EHK (complex IV, Thermus thermophilus), and 2CCY (cytochrome c, Rhodospiril-lum molischianum).

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Figure 2 (Chapter 4)
Sequences and structures of representative archaeal chromatin proteins. Primary sequences of HMfB from M. fervidus (A), Sul7d (Sac7d) from S. acidocaldarius (B), Alba (Sso10b1) from S. sol-fataricus (C), and MC1 from Methanosarcina sp. CHTI55 (D) are shown below the corresponding protein structure. The figure was constructed using structures available from the Protein Data Bank (11). Regions with α-helical and β-strand structures are colored identically in the sequence and in the corresponding structure.

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Figure 3 (Chapter 6)
Subunit structure of RNAPs from the three domains of life. The largest subunit in the Eucarya and β’ in the Bacteria is split into two subunits, A1 and A2, in the Archaea. In methanogens, subunit B is also split into two polypeptides, B’ and B″. Different parts of bacterial subunit α are encoded by the genes for the archaeal subunits D and L. Subunits E1, F, H, N, and P are only shared between the Archaea and Eucarya. The pattern shown is based on separation of subunits by polyacrylamide gel electrophoresis under denaturing conditions. The numbers in the subunits of the eucaryal RNAP A (I), B (II), and C (III) indicate the molecular mass.

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Figure 4 (Chapter 6)
Structural similarity of Pyrococcus RNAP (A) and yeast RNAPII (B). Comparison of interactions of an archaeal RNAP inferred from Far-Western analysis with interactions of yeast RNAPII observed in the crystal structure of the enzyme. The width of the lines connecting subunits is a measure of the intensity of the interaction. Modified from Science (27) with additional data from Proceedings of the National Academy of Sciences USA (2).

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Figure 3 (Chapter 8)
Organization of the main ribosomal protein gene clusters in archaeal genomes. SSO, Sulfolobus sol-fataricus; STO, Sulfolobus tokodaii; AFU, Archaeoglobus fulgidus; APE, Aeropyrum pernix; PFU, Pyrococcus furiosus; PHO, Pyrococcus horikoshii; PAB, Pyrococcus abyssi; TKO, Thermococcus kodakaraensis; PAE, Pyrobaculum aerophylum; MKA, Methanopyrus kandleri; MMA, Methanosarcina mazei; MAC, Methanosarcina acetivorans; MTH, Methanothermobacter thermautotrophicus; MJA, Methanococcus jannaschii; MMP, Methanococcus maripaludis; HMA, Haloarcula marismortui; H-sp, Halobacterium sp. NRC1; TAC, Thermoplasma acidophilum; TVO, Thermoplasma volcanii. The last line (ECO) shows for comparison the organization of the same genes in E. coli that is also present in most bacteria. Genes that are within 50 bp of each other, and may therefore be cotranscribed, are indicated in the same color. Domain-specific genes are underlined.

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Figure 4 (Chapter 9).
Crystal structure of the M. thermautotrophicus GatDE complexed with tRNAGln. The dimer of the heterodimeric GatDE (thus forming a heterotetramer) binds two tRNA molecules. The asparaginase active site of GatD and the kinase/amidotransferase active site of GatE are distantly separated, connected with a “molecular tunnel.”

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Figure 3 Chapter10.
Structure of archaeal group II chaperonin from Thermoplasma acidophilum. (A and B) The side view and top view of the crystal structure of T. acidophilum chaperonin, respectively. The α subunits are shown in dark green, and the β subunits are shown in dark blue. The hexadecameric structure was drawn using MOLSCRIPT (48). (C) The subunit structure of T. acidophilum chaperonin. Apical, intermediate, and equatorial domains are represented by green, blue, and red, respectively. The helical protrusion is highlighted by yellow. The figure was drawn with the Viewer Light 5.0 software (Accelrys).

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Figure 16 (Chapter 14).
Transmission electron micrographs of P. occultum. (a) Pyrodictium cells after freeze etching, exhibiting an S-layer with p6 symmetry. Bar = 0.5 μm. (b) Extracellular cannulae, a specific feature of the genus Pyrodictium; negative staining with uranyl acetate; bar = 0.1 μm. (c) 3D tomogram of a frozen-hydrated Pyrodictium cell with two cannulae; bar = 0.2 μm. Modified from the Journal of Structural Biology (106) with permission of the publisher.

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Figure 3 (Chapter 17).
. Crystal structure of the M. jannaschii Sec61 protein-conducting channel. Views from the top (a) and the front (b). Faces of the helices that form the signal-sequence-binding site and the lateral gate through which TMs of nascent membrane proteins exit the channel into lipid are colored. The plug, which gates the pore, is green. The hydrophobic core of the signal sequence probably forms a helix, modeled as a magenta cylinder, which intercalates between TM2b and TM7 above the plug. Intercalation requires opening the front surface as indicated by the broken arrows, with the hinge for the motion being the loop between TM5 and TM6 at the back of the molecule (5/6 hinge). A solid arrow pointing to the magenta circle in the top view indicates schematically how a TM of a nascent membrane protein would exit the channel into lipid. Structure and legend reprinted from Nature (107) with permission from the publisher.

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Figure 8 (Chapter 18)
Overview of halobacterial signal transduction. Transducer proteins (Htr proteins) are depicted as dimers (brown) and shown in their expected topology. The Htr regions involved in adaptation (yellow) and in signal relay (dark gray) to the flagellar motor via various Che proteins are indicated. The actions of the Che-protein machinery are illustrated for only one of the Htr proteins, shown on the left, for which an interaction with a substrate-loaded, membrane-anchored binding protein is indicated. CheD and CheJ (CheC) proteins are omitted for clarity. Htr1 and Htr2 transduce light signals via direct interaction with their corresponding receptors SRI and SRII. Repellent light signals mediated by SRI and SRII elicit the release of switch factor fumarate from a membrane-bound fumarate pool. MpcT senses changes in membrane potential (Δψ) generated via light-dependent changes in ion transport activity of BR and HR. The relative sizes of receptors, binding proteins, transducers, and Che proteins approximately reflect their corresponding molecular masses. Reproduced from Molecular Microbiology (54) with permission of the publisher and D. Oesterhelt.