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.

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