archaea       
noun [ plural ]  biology specialized (also Archaea) uk/ɑːˈkiː.ə/ us/ɑːrˈkiː.ə/
 古菌
a type of microorganism (= extremely small living thing) similar to bacteria but with a different structure, thought to have existed for billions of years
  Archaea have an ancient lineage, splitting off from bacteria probably about 2 billion years ago.  古菌溯源久远,与细菌分支大约发生在二十亿年前。 
 Learning more about Archaea could answer questions about the origins of life on Earth.  对古菌有更多的了解可以回答有关地球生命起源的问题。 
 - More examples
 - In the archaea, there is no nucleus.
 - Archaea are part of the intestinal flora of humans and float in pockets of pressurized water in the Earth's crust.
 - As much as 10 percent of the Earth's biomass lives below ground, including single-celled bacteria called archaea that feed on decaying matter.
 - There are some Archaea that are only found in coal heaps, which makes you wonder what they did before we started mining coal.
 - The researchers found that two litres of seawater contained nearly 37,000 different kinds of bacteria and nearly 3,000 types of archaea, ancient single-celled organisms.