How do Archaea tolerate the heat? Proteins stabilized by more ionic bridges between amino acid...
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Transcript of How do Archaea tolerate the heat? Proteins stabilized by more ionic bridges between amino acid...
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
Cell Membrane Structure
O O
O O
R
R
O O
O O
R
R
Composed of diglyceridesR group may be phosphate, sulfate, or sugarLong 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
Cell Structure: Movement
anchoragerotation
basal rings and rod
stiff helical flagellum
is rotated by “motor apparatus”in the membrane by H+ ATPaseat rates of 200-1700 rps (>12,000 rpm!)
hookdirectional rotation?
flagellin protein
Taxis: movement toward stimulus
phototaxis: movement toward light
chemotaxis: movement to chemicals
Motile Archaea often have multiple flagella in a tuft at one place on the cell surface
thermotaxis: movement to heat
Cell Structure: Nucleoid
transcription by RNA polymerase (~POLII@TATA)
one circular DNA molecule + plasmidshistone-like protein association (~eukaryotic)genome smaller than typical bacteriasequences closer to eukaryotic homologsintrons in rRNA and tRNA genesoperon regulation in some genes like bacteriaattached to cell membrane
separation of chromosomes
replication by DNA polymerase
Nucleoid - genome
translation of mRNA into protein
rRNA + protein + ribozymes
70S Ribosomecytokinesis by furrowing
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
Replicons - small circular DNAs with additional essential genes
Nucleoid - main chromosome is circular but associated with histone-like proteins
• 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
http://biology.kenyon.edu/Microbial_Biorealm/archaea/halobacterium/halobacteria_1.jpg
3 chromosomesMain chromosome 2,015 kb191 kb replicon366 kb replicon
Replicons have genes for:DNA polymeraseTranscription factorsMineral uptake (K, PO4)Cell division
The genome has many insertion sites for foreign genes
Bacteriorhodopsin:Protein + retinalAmax 280 UV, 570 green nmenergy for proton transport and phosphorylation without photosynthesis!
Halobacterium salinarium
Aerobic RespirationUp to 5 M (25% NaCl)!Great Salt Lake, UtahRed Sea, Asia Minor
www.hawaii.edu/microbiology/ Alam/publications/PNAS96-ZHANG.pd
Cytoplasm
Periplasmicspace
CellMembraneRetinal
lsu.epfl.ch/sh/bR_full.pdf
Bacteriorhodopsin absorbs green from the visible spectrum, so what color is the pigment?
Hint: it reflects the other colors of the spectrum
• Photoautotrophism
• Photoheterotrophism
• Chemoautotrophism
• Chemoheterotrophism
Which of these metabolic pathwaysis Halobacterium demonstrating?
√
Hint:
• Light for energy
• Chemicals for carbon
http://www.bact.wisc.edu/Bact303/Methanococcus.jpeg
Methanococcus jannischii
Isolated from “white smoker” hydrothermal vent2600m deep on the East Pacific Rise
MethanogenObligate anaerobeH2 as energy sourceCO2 as carbon sourceCH4 as byproduct of metabolismTemperature: 50-86°C
Other species found incow rumen (first stomach)Cow belches 50 L of methane per day
What does this electron micrograph tell you?
…about cell shape?
…about motility?
• Photoautotrophism
• Photoheterotrophism
• Chemoautotrophism
• Chemoheterotrophism
Which of these metabolic pathwaysis Methanococcus demonstrating?
√
Hint:
• H2 for energy
• CO2 for carbon
http://www.molgen.mpg.de/~ag_ribo/ag_franceschi/franceschi-projects-30S.html
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
Thermus aquaticus
Gram negative
Thermophile isolated from Yellowstone Hot SpringOptimum temperature 85°C
Stability of macromolecules excellentEnzymes for research or commercial useTaq polymerase is the enzyme of PCR (Polymerase Chain Reaction)
Lives near cyanobacteria which feed Thermus
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
http://sci.agr.ca/crda/images/BACTERI1.JPG
• Photoautotrophism
• Photoheterotrophism
• Chemoautotrophism
• Chemoheterotrophism
Which of these metabolic pathwaysis Thermus demonstrating?
√Hint:
• Organic chemicals for energy
• Organic chemicals for carbon
http://dac.molbio.ku.dk/Sulfolobus.jpg
Sulfolobus acidocaldarius
75°C Optimum
Strict aerobe
pH 1 to 6
Oxidize Sulfur or can use Fe2+ or MnO4
2- as electron acceptors…uses glycolysis and TCA cycle
Pilus and conjugation plasmids not similar to bacterial ones
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
• Photoautotrophism
• Photoheterotrophism
• Chemoautotrophism
• Chemoheterotrophism
Which of these metabolic pathwaysis Sulfolobus demonstrating?
√Hint:
• Organic chemicals for energy
• Organic chemicals for carbon