Archaea

Archaea

“Tree of Life”

• Woese’s Tree of Life

• Archaea = newly defined group (based on DNA sequences)

Archaea

“Archaea” = “ancient” (Greek)

• Evolved in extreme ancient environments (Archaea, then Hadian era)

• Still thrive in extreme environments today

Key traits

• Diverse in size and shape - some similar to bacteria, some unique (cube)

• Similar reproductive modes: binary fission, fragmentation, budding (small organisms grow off another, then it usually breaks off and is its own organism)

• Heterotrophic and autotrophic (never both) (autotrophy archaea can generate energy from sulfur and methane)

• Abundant: also important in nutrient cycling, especially in ocean

Prokaryotes most closely related to eukaryotes

Unique chemistry:

1. More similar to eukarya than bacteria in Woese’s rRNA analysis

   • Both in sequence and in process (similar enzymes)

   • (such as transcription and translation works similarly)

2. Plasma membrane different from bacteria AND eukaryotes

   • Still a fluid mosaic membrane, but unique organization and chemical composition

     1. Allows survival in extreme environments

     2. Does not include peptidoglycan (unlike bacteria, only bacteria have peptidoglycan in their membrane)

Currently classified into 3-4 main groups molecularly

1. Euryarchaeota

2. Crenarachaeota

3. Korarchaeaota

4. Nanoarchaeota (sometimes combined with #3, debated amongst scientists if it should be its own group or not)

• Too diverse for kingdoms or phyla

• Instead = phylogenetic “groups”

Another way to classify = 3 groups based on physiology (and corresponding habitat):

1. Methanogens

   1. Live in guts and swamps (dark, moist, anoxic)

   2. Make methane

   3. Greenhouse gases attribute to sheep and cattle (they’re getting linked to greenhouse gases because they have archaea in their guts that are making these products and releasing them to the atmosphere)

   4. In 50% of human guts (genetic and environment factors play a role, not 100% certain as to why anymore)

      1. Both genetic and environmental factors

2. Extremophiles

   1. Live in extreme habitats (phile = love)

   2. Examples:

      1. Acidophiles: acidic pools as lows as pH of 1

      2. Thermophiles: hot water springs up to 111 degrees Celcius

      3. Halophiles: salinity > 25% (such as inside salt-crystals)

      4. Psychophiles: love the cold - polar vortex fans

      5. Barophiles: love high-pressure (such as deep sea)

3. Mesophiles

   1. Normal, non-extreme habitats (middle-lovers)

   2. Found all over (soil, lakes, etc.)

   3. The “boring” archaea

4. Possible group: archaea in space?

   1. Halophilic archaea survive in orbit

   2. Evidence of salt water on mars

   3. AKA astrophiles