Archaea Exam 3

Why do we use the 16s sequence to compare and identify prokaryotes?

The 16s rRNA acts as a molecular barcode for prokaryotes

• They are highly conserved and found in all bacteria and archaea making it the universal marker

What is 16s apart of?

Small subunit of 70s ribosome

Are archaea bacteria?

No

What is the structure of the cell wall made of in archaea and how is it different than bacteria and eukaryotes?

They are made of psuedomurein/psuedopeptidoglyan

Can you gram stain an archaea? Why or why not?

No, their walls are not made out of peptidoglycan so their gram stain pattern means nothing

• Cell walls are also not affected by enzymes that break down peptidoglycan nor antibiotics that poison synthesis of peptidoglycan

How are the lipids different in archaea? What are their bond types?

They have hydrocarbon tails attached to glycerol by ETHER bonds. They have saturated hydrocarbon chains with rings instead of fatty acid chains

• These are stronger so they perform better in extreme environments

• The saturated hydrocarbon chains make the cell walls more resistant to harsh conditions

Why are monolayer membranes beneficial?

More rigid and better able to resist harsh environments

• prevent membranes from leaking

How do archaea membranes adapt to the temperature fluctuations?

They modify their membranes

What features do archaea share with bacteria and eukaryotes?

Similarities with BACTERIA-

1. Circular double stranded DNA genome & haploid

2. Polycistronic

3. Horizontal gene transfer, binary fission

4. Highly diverse metabolic pathways for energy production

   Similarities with EUKARYOTES-

   1. More than one origin of replication

   2. Histones and nucleosomes

   3. INTRONS

   4. Many RNA poly

   5. Many translation factors and some shared ribosome proteins
      

What are the two most well described phyla of archaea?

Crenarchaeota

Euryarchaeota

Which type of archaea live in humans and are they extremophiles?

Mesophiles, they are not extremophiles

What are methogens?

Strictly anaerobes

• produce methane (CH4) by reducing carbon compounds like CO2 or acetate

• They love environments rich in nutrients like human intestines, sludge digestors, and swamps

Do archaea currently cause diseases in humans?

No archaea are pathogenic or parasitic

What are halobacteria?

• NO CELL WALLS ONLY S-LAYERS

• require salt or they will die by lysis

• aerobic

• pigments and high salt provide radiation protection

Do halophiles have a cell wall, if not, what do they have?

S-layer

What do halobacteria use rhodopsin for?

They have 3 main functions

• Bacteriorhodopsin (“visual purple”)-

generates ATP from light energy and has a purple membrane that functions in aggregation of bacteriorhodopsin

• Halorhodopsin-

maintains intracellular concentrations of salts

• Sensory Rhodopsin-

photoreceptors, can control flagella and phototaxis

Do thermoplasma have cell walls? If not, what do they have and where do they live?

NO CELL WALLS ONLY S-LAYERS

• Hot acidic springs with pH 1 to 2

• extremely though plasma layers

• tough EXTERNAL S-LAYERS

Which type of archaea can grow in above boiling temperatures?

Hyperthermophiles Thermococcus kodakarensis

88C to 102C

• Has reverse gyrase, induces positive supercoiling in DNA and makes DNA more resistant to thermal denaturing

Where are hyperthermophiles?

Live in oceanic volcanic vents

Where are barophiles?

Live at the bottom of the ocean

Where are mesophiles?

Live in the human gut but are not extremophiles

How do archaea membranes adapt to lower temp: colder, membrane less fluid

More unsaturated lipids, less ring structures, shorter lipids; maintains fluidity

How do archaea membranes adapt to a higher temp: warmer and membrane too fluid

More saturated lipids, more ring structures, longer lipids, decreases fluidity

What are the crenarchaeota?

They are extremeophiles so you would find them in extreme environments.

MORE LIKELY TO BE HYPERTHERMOPHILES AND ACIDOPHILES

• Consists of thermophiles/hyperthermophile, psychrophiles. acidophiles

• S0 oxidizers and reducers

What are Euryarchaeota?

Most diverse extremophiles

MORE LIKELY TO BE HALOPHILES AND METHANOGENS

• Consist of thermophiles, METHANOGENS, acidophiles, HALOPHILES

• Sulfate reducers

What are some ecological importance of methanogens?

• important in wasteland treatment

• dangerous in landfills- highly flammable and explosive

• produce signifigant amounts of methane, can be a fuel or energy source

• may contribute to global warming

• higher amounts of methanogens in the intestines correlates with the inability to lose weight

What are the benefits of methanogens in wastewater treatment?

• reduces sludge volume (breaks solids into gas and water)

• generates biogas (methane rich gas can be captured and used as renewable energy

• lowers odors (removes foul smelling compounds)

• reduces pathogens (anaerobic digestion helps kill disease-causing microbes)

• sustainable disposal (reduces need for landfill disposal of sludge)

What type of relationship do crenarchaeotas have?

Symbiotic in hot acidic microbial mats

• Thermophile and acidophiles both require sulfur

What are sulfolobus and thermopoteus and what phyla of archaea are they in?

Thermoacidophiles

1. Sulfolobus- AEROBIC HETEROTROPH, grows in hot aidic sulfurous springs —→ OXIDIZE SULFUR to H2SO4

2. Thermoproteus- REDUCES S0 to H2S ——> ANAEROBIC

What are the 5 major groups more diverse than the Crenarchaeota?

1. Methanogens (non-extremophile)

2. Halobacteria

3. Thermoplasms

4. Hyperthermophiles

How do you classify methanogens?

STRICT (obligate) ANAEROBES

Pyrococcus furiosus: rushing fireball

• Hyperthermophile ANAEROBE from deep sea volcanic vents REDUCE SULFUR

• Has reverse gyrase (more resistant to thermal denaturing)

• High transformation ability

Archaeoglobus fulgidus (ancient sphere because of its fluorescents under UV)

NO CELL WALL they have a crystalline S-layer arranged in hexagonal array