What are archaeans?
Archaea were discovered in the early 1970s. Similar to bacteria they are single-celled prokaryotes. Archaeans DNA structure places it in a separate kingdom. There is still much about archaeans that are not known. What we do know is that most of them can survive in highly extreme environments and are known as extremophiles.
We can’t observe archaeans with the naked eye, it is an extremely small organism which has to be observed under the microscope. Archaea have the variety of shapes including cocci (round), bacilli (rod-shaped), and irregular shapes. Archaeans cell structure has a typical prokaryotic cell anatomy: plasmid DNA, cell wall, cell membrane, cytoplasm, and ribosomes. Some archaeans also have long, whip-like protrusions called flagella, which aid in movement.
Archaea now is a separate domain. Under the archaea domain, there are three main divisions. They are Crenarchaeota, Euryarchaeota, and Korarchaeota.
Crenarchaeota consist mostly of hyperthermophiles and thermoacidophiles. Hyperthermophilic microorganisms live in extremely hot or cold environments. Thermoacidophiles are microscopic organisms that live in extremely hot and acidic environments. Their habitats have a pH between 5 and 1. You would find these organisms in hydrothermal vents and hot springs. Crenarchaeota species examples of crenarchaeotes include: Sulfolobus acidocaldarius – found near volcanic environments in hot, acidic springs containing sulfur. Pyrolobus fumarii – live in temperatures between 90 and 113 degrees Celsius.
Euryarchaeota organisms consist mostly of extreme halophiles and methanogens. Extreme halophilic organisms live in salty habitats. They need salty environments to survive. You would find these organisms in salt lakes or areas where sea water has evaporated. Methanogens require oxygen-free (anaerobic) conditions in order to survive. They produce methane gas as a byproduct of metabolism. You would find these organisms in environments such as swamps, wetlands, ice lakes, the guts of animals (cow, deer, humans), and in sewage. Euryarchaeota species examples of euryarchaeon include: Halobacterium – include several species of halophilic organisms that are found in salt lakes and high saline ocean environments. Methanococcus – Methanococcus jannaschii was the first genetically sequenced Archaean. This methanogen lives near hydrothermal vents. Methanococcoides burtonii – these psychrophilic (cold-loving) methanogens were discovered in Antarctica and can survive extremely cold temperatures.
Korarchaeota organisms are thought to be very primitive life forms. Little is currently known about the major characteristics of these organisms. We do know that they are thermophilic and have been found in hot springs and obsidian pools.