Topic 3: Archaea

Question 1

Carl Woese

Answer 1

• Carl Woese was the first to identify and demonstrate how the Archaea form their own distinct branch in the tree of life
• Carl Woese and George Fox 1970s
• Discovered by sequencing RNA

Question 2

Archaea and Bacteria Common Features (6)

Answer 2

1. Size and shapes
2. Shared biomarkers
3. Inclusion bodies
4. Circular chromosome (for most)
5. Nucleoid region
6. Cytoskeleton (for some)

Question 3

Archaea and Eukaryotes Common Features (3)

Answer 3

1. One of their polymerases
2. Histone proteins
   —-Both eukaryotes and archaea have histone proteins, but eukaryotes have a slightly different arrangement of DNA around the histone proteins.
3. Cytoskeleton (for some)

Question 4

Methanogens

Answer 4

• Methane producing organisms
• Euryarchaeota contains all known methanogens
• Live in oxygen-poor environments (e.g., digestive tracts, cecum, rumen, hydrothermal vents, waste water sludge, termite guts)
• Energy Sources:
  —Hydrogenoclastic methanogens use hydrogen as an energy source. There are the most common group of methanogens in the environment
  — Acetoclastic use acetate
  — Methylotrophic use methanol
  -Volta Experiment shows how much energy is present in the form of heat and light.

Question 5

Extremophiles

Answer 5

• Halophiles (high salt)
• Thermophiles (temp over 55C)
• Hyperthermophiles (temp over 80C)
• Acidophiles (acidic environment)
• Barophiles (high pressure)

Question 6

Phyla of the Archaea

Answer 6

T
- Thaumarchaeota
–Most abundant organisms on Earth
N
- Nanoarchaeota
–Only one member
E
- Euryarchaeota
–Methanogens
C
- Crenarchaeota
–Extremophiles
K
- Korarchaeota
– Newly recognized phylum

Question 7

Thaumarchaeota

Answer 7

• Low-temperature archaea extremely important for the cycling of nutrients (e.g., carbon and nitrogen) and production of vitamins in the ocean
• In ocean, outnumber bacteria, especially at greater depths

Question 8

Halophiles

Answer 8

• Euryarchaeota
• salt loving
  found in ponds where water evaporates
• Survive high-salt (sodium) conditions by concentrating another salt, potassium, within their cells
  — Has more guanine and cytosine content in its genome to stabilize DNA in presence of so much potassium
• Red colour comes from retinal, which captures light energy

Question 9

Nanoarchaeum

Answer 9

• One member: Nanoarchaeum equitans
  – Possibly smallest microorganism
  – Discovered in hydrothermal vent north of Iceland
  – Associates with Ignicoccus hospitalis
  Possible parasite:
  — No metabolic genes
  — Can’t make ATP
  — Can’t make amino acids
  — Can’t make nucleotides
  — Can’t make lipids for its membrane
  — DOES produce S-layer

Question 10

Shapes of cells found within archaea

Answer 10

Rods, cocci, spirals (similar to bacteria)

Irregular shapes (Sulfolobus spp.)

Rectangular shapes (Thermoproteus spp.)

Squares (Haloquadratum walsbyi)

Question 11

Explain how Halo bacterium tolerates high salinity

Answer 11

• Halobacterium are halophiles (salt-loving) bacteria
• They can tolerate high salinity because a very high intracellular [K+] offers a high extracellular [Na+]
• The ions balance and there is no net gain or loss of water
• high intracellular concentration of potassium (K+) can denature proteins and split DNA
• Phototrophic

Question 12

Explain where you would find methanogens and why

Answer 12

• In the phylum Euryarchaeota
• Produce methane
• Strict anaerobes
  Found in:
• Anoxic sediments (marshes/swamps, lakes, rice paddies, moist landfill)
• Animal digestive tracts
• Found in Low oxygen environments (Gut, swamps)
• Geothermal H2/CO2 sources
• Artificial biodegradation facilities

Question 13

Describe why the relationship between Nanoarchaeum and Ignicoccus is “bizarre”

Answer 13

• Parasitic nanoacheraeum acts as a s-layer or membrane to the host ignicoccus
• It surrounds and covers the ignicoccus
• Not confirmed symbotic relationship because cant make lots of things