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Archaeans color a hot spring in Yellowstone N. P.
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Archaebacteria is an obsolete taxonomic name. Since the wide acceptance of a three-domain system of life, the organisms formerly designated by that name have been placed in a separate domain, named Archaea.
Archaea is one of two prokaryote domains, the other being Bacteria. Only the single-celled organisms assigned to the domain Bacteria are now called bacteria. The organisms in Domain Archaea, formerly also called bacteria, are now known as archaeans.
The various microbes assigned to the two domains Archaea and Bacteria are generally similar in size, shape and appearance. They differ markedly, however, at the genetic level. For example, they're about as distinct from each other with respect to their ribosomal RNA sequences as is either from a eukaryote (Eukaryota is the third of the three currently recognized domains of life).
The archaea can utilize a much broader range of energy sources than bacteria. In fact, they were initially identified as organisms that lived in extreme environments, such as hot springs or salt lakes. However, they are now known to occur in many other types of environments.
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