Archaea
Non-bacteria prokaryotes
Archaea are microscopic, single-celled, prokaryotic organisms. They were originally called archaebacteria, but are distantly-related to bacteria, and possess genes more closely related to those of eukaryotes. Archaea do not use sunlight to fix carbon, and use more energy sources than other autotrophs. They are a major component of ocean plankton
Features
Possess genes that are more closely related to those of eukaryotes, such as the enzymes involved in transcription and translation
The Asgard archaea (Asgardarchaeota), and specifically the order Hodarchaeales is most closely related to eukaryotes (Eme et al. 2023)
Archaea use more energy sources than eukaryotes
Organic compounds, such as sugars
Ammonia
Metal ions
Hydrogen gas
Unlike plants/algae and cyanobacteria, archaea do not use sunlight to "fix carbon"
Archaea do not produce spores like many bacteria and eukaryotes
Many are soil dwelling in extreme environments, but not all
Geologic Age
Archean - present
Above: Thermophilic archaea in the Midway Geyser Basin in Yellowstone National Park
Questions for thought:
What are Archaea?
How are they different from the other domains?
Where could I find Archaea?
What important role do they play in the environment?
Additional Reading:
Eukaryotes may all derive from an Asgard ancestor (Futurity 23Jun2023; peer-reviewed Eme et al. 2023)
3.42-billion-year-old fossil threads may be the oldest known archaea microbes (Science News 26Jul2021; peer-reviewed Science Advances )
Complex archaea that bridge the gap between prokaryotes and eukaryotes (Nature 6May2015)