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. 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 R
If C40, the membrane is a monolayer O R
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 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
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. Replicons have genes for: DNA polymerase Transcription factors
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
archaea/halobacterium/halobacteria_1.jpg
Aerobic Respiration
Up to 5 M (25% NaCl)!
Great Salt Lake, Utah
Red Sea, Asia Minor

7. Hint: it reflects the other colors of the spectrum
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
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
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
ag_franceschi/franceschi-projects-30S.html

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

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