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How do Archaea tolerate the heat? • Proteins stabilized by more ionic bridges between amino acid r-groups and more-hydrophobic core amino acids • Heat shock protein (chaperonins) refold denatured proteins…Pyrococcus 121°C for 1 hour! • DNA depurination reduced by presence of 2,3diphosphoglycerate. • DNA supercoiling by reverse gyrase reduces denaturation • Sac7d in Sulfobolus is a minor groove protein increases the melting temperature by 40°C • Histone-like proteins help stabilize DNA as well • Heat-resistant di-bi-phytanyl diether lipid membranes (monolayer) prevent delamination of membrane Cell Membrane Structure Composed of diglycerides R group may be phosphate, sulfate, or sugar Long chain branched hydrocarbon (not fatty acid) Hydrocarbons may be C20 or C40 If C20, the membrane is a bilayer: O O O O R R If C40, the membrane is a monolayer O O O O R R In some species, the membrane is a mixture of both C20 and C40 diglycerides forming a mixed mono-/bi-layer Cell Structure: Movement hook basal rings and rod directional rotation? anchorage rotation stiff helical flagellum flagellin protein is rotated by “motor apparatus” in the membrane by H+ ATPase at rates of 200-1700 rps (>12,000 rpm!) Motile Archaea often have multiple flagella in a tuft at one place on the cell surface thermotaxis: movement to heat Taxis: movement toward stimulus phototaxis: movement toward light chemotaxis: movement to chemicals Cell Structure: Nucleoid Nucleoid - genome one circular DNA molecule + plasmids histone-like protein association (~eukaryotic) genome smaller than typical bacteria sequences closer to eukaryotic homologs introns in rRNA and tRNA genes operon regulation in some genes like bacteria attached to cell membrane transcription by RNA polymerase (~POLII@TATA) replication by DNA polymerase separation of chromosomes cytokinesis by furrowing 70S Ribosome rRNA + protein + ribozymes translation of mRNA into protein Process called binary fission NOT mitosis! •Genome and copy are identical •Genome is haploid •There is no synapsis •There is no recombination Cell Structure: Genetic Structure Nucleoid - main chromosome is circular but associated with histone-like proteins Replicons - small circular DNAs with additional essential genes • Genes are generally in clusters in operon-like situations • Chromosomes have insertion sites for transposition events • rRNA and other genes have intron sequences • How the movements of the multiple units is coordinated is not yet fully known Halobacterium salinarium http://biology.kenyon.edu/Microbial_Biorealm/ archaea/halobacterium/halobacteria_1.jpg Aerobic Respiration Up to 5 M (25% NaCl)! Great Salt Lake, Utah Red Sea, Asia Minor 3 chromosomes Main chromosome 2,015 kb 191 kb replicon 366 kb replicon Replicons have genes for: DNA polymerase Transcription factors Mineral uptake (K, PO4) Cell division The genome has many insertion sites for foreign genes Bacteriorhodopsin: Protein + retinal Amax 280 UV, 570 green nm energy for proton transport and phosphorylation without photosynthesis! Periplasmic space Retinal Cell Membrane lsu.epfl.ch/sh/bR_full.pdf Cytoplasm www.hawaii.edu/microbiology/ Alam/publications/PNAS96-ZHANG.pd Bacteriorhodopsin absorbs green from the visible spectrum, so what color is the pigment? Hint: it reflects the other colors of the spectrum Which of these metabolic pathways is Halobacterium demonstrating? • Photoautotrophism √ • Photoheterotrophism • Chemoautotrophism • Chemoheterotrophism Hint: • Light for energy • Chemicals for carbon Methanococcus jannischii Isolated from “white smoker” hydrothermal vent 2600m deep on the East Pacific Rise http://www.bact.wisc.edu/Bact303/Methanococcus.jpeg What does this electron micrograph tell you? …about cell shape? …about motility? Methanogen Obligate anaerobe H2 as energy source CO2 as carbon source CH4 as byproduct of metabolism Temperature: 50-86°C Other species found in cow rumen (first stomach) Cow belches 50 L of methane per day Which of these metabolic pathways is Methanococcus demonstrating? • Photoautotrophism • Photoheterotrophism √ • Chemoautotrophism • Chemoheterotrophism Hint: • H2 for energy • CO2 for carbon Thermus aquaticus QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. http://www.molgen.mpg.de/~ag_ribo/ ag_franceschi/franceschi-projects-30S.html QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Gram negative Thermophile isolated from Yellowstone Hot Spring Optimum temperature 85°C Stability of macromolecules excellent Enzymes for research or commercial use Taq polymerase is the enzyme of PCR (Polymerase Chain Reaction) Lives near cyanobacteria which feed Thermus http://sci.agr.ca/crda/images/BACTERI1.JPG Which of these metabolic pathways is Thermus demonstrating? • Photoautotrophism • Photoheterotrophism • Chemoautotrophism √ • Chemoheterotrophism Hint: • Organic chemicals for energy • Organic chemicals for carbon Sulfolobus acidocaldarius 75°C Optimum Strict aerobe pH 1 to 6 QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. http://dac.molbio.ku.dk/Sulfolobus.jpg Oxidize Sulfur or can use Fe2+ or MnO42- as electron acceptors…uses glycolysis and TCA cycle Pilus and conjugation plasmids not similar to bacterial ones Which of these metabolic pathways is Sulfolobus demonstrating? • Photoautotrophism • Photoheterotrophism • Chemoautotrophism √ • Chemoheterotrophism Hint: • Organic chemicals for energy • Organic chemicals for carbon