How do Archaea tolerate the heat?

1. 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 2,3-diphosphoglycerate. • 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

2. R R R R O O O O O O O O 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: If C40, the membrane is a monolayer In some species, the membrane is a mixture of both C20 and C40 diglycerides forming a mixed mono-/bi-layer

3. Cell Structure: Movement hook directional rotation? basal rings and rod 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!) Taxis: movement toward stimulus Motile Archaea often have multiple flagella in a tuft at one place on the cell surface phototaxis: movement toward light thermotaxis: movement to heat chemotaxis: movement to chemicals

4. 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 • Process called binary fission • NOT mitosis! • Genome and copy are identical • Genome is haploid • There is no synapsis • There is no recombination rRNA + protein + ribozymes translation of mRNA into protein

5. 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

6. 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! 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

7. Periplasmic space Cell Membrane Retinal lsu.epfl.ch/sh/bR_full.pdf Cytoplasm Bacteriorhodopsin absorbs green from the visible spectrum, so what color is the pigment? Hint: it reflects the other colors of the spectrum www.hawaii.edu/microbiology/ Alam/publications/PNAS96-ZHANG.pd

8. Which of these metabolic pathways is Halobacterium demonstrating? • Photoautotrophism • Photoheterotrophism • Chemoautotrophism • Chemoheterotrophism √ Hint: • Light for energy • Chemicals for carbon

9. Methanococcus jannischii Isolated from “white smoker” hydrothermal vent 2600m deep on the East Pacific Rise 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 http://www.bact.wisc.edu/Bact303/Methanococcus.jpeg What does this electron micrograph tell you? …about cell shape? …about motility?

10. Which of these metabolic pathways is Methanococcus demonstrating? • Photoautotrophism • Photoheterotrophism • Chemoautotrophism • Chemoheterotrophism √ Hint: • H2 for energy • CO2 for carbon

11. Thermus aquaticus 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://www.molgen.mpg.de/~ag_ribo/ ag_franceschi/franceschi-projects-30S.html http://sci.agr.ca/crda/images/BACTERI1.JPG

12. Which of these metabolic pathways is Thermus demonstrating? • Photoautotrophism • Photoheterotrophism • Chemoautotrophism • Chemoheterotrophism √ Hint: • Organic chemicals for energy • Organic chemicals for carbon

13. Sulfolobus acidocaldarius 75°C Optimum Strict aerobe pH 1 to 6 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 http://dac.molbio.ku.dk/Sulfolobus.jpg

14. Which of these metabolic pathways is Sulfolobus demonstrating? • Photoautotrophism • Photoheterotrophism • Chemoautotrophism • Chemoheterotrophism √ Hint: • Organic chemicals for energy • Organic chemicals for carbon