The Greek word archaios means original. Archaea are primitive bacteria. Archaea that prefer temperature are called thermophiles. 84 degrees C. They die in the heat. 98 degrees C. They grow well at temperature. They are 110 degrees Celsius. Lasts up to temp. For example, Methanopyrus. Archaea that love heat and acid are called thermoacidophiles. Archaea that prefer salt are called halophiles.
Genome sequencing in 1996 revealed that more than half of the 1,738 genes in archaea are distinct from bacteria and other organisms. Members of Archaea that produce methane in their metabolism are called Methanogens. The process of making methane is called Methanogenesis.