archaea

plural noun

ar·​chaea är-ˈkē-ə 

: usually single-celled, prokaryotic microorganisms of a domain (Archaea) that includes methanogens and those of harsh environments (such as acidic hot springs, hypersaline lakes, and deep-sea hydrothermal vents) which obtain energy from a variety of sources (such as carbon dioxide, acetate, ammonia, sulfur, or sunlight)

Characterized under the heading archaea, these creatures have an amazing lineage that extends deep in the geologic record to the twilight of Earth's organic origins.

—Todd Wilkinson

… although archaea organize their DNA much as bacteria do (they also have no cell nucleus, for example), many aspects of the way the DNA gets processed are distinctly different. Instead, the processing is more similar to what goes in within eukaryotic cells.

—Olivia Judson

Many of the archaea are thermophilic. These amazing "extremophiles" eke out a living in environments in which no other organism can survive.

—David W. Wolfe

see archaean compare bacterium, eukaryote

archaeal

är-ˈkē-əl 

adjective

Hot springs in Yellowstone National Park have revealed head-spinning levels of archaeal diversity—including a pair of organisms that are the most primitive forms of life alive today.

—Carl Zimmer

… the archaeal proteins responsible for several crucial cellular processes have a distinct structure from the proteins that perform the same tasks in bacteria.

—W. Ford Doolittle

Examples of archaea in a Sentence

Recent Examples on the Web

Over the past few decades, a two-domain tree has prevailed, in which eukaryotes emerged from within archaea rather than alongside them. —Quanta Magazine, 28 Oct. 2024

Sixty science units include an experiment focused on human bone cells and another carrying anaerobic archaea, which will look at viability and methane production of early terrestrial life in a simulated cosmic environment, Space News reports. —Stephen Clark, Ars Technica, 19 Jan. 2024

The University of Hawaii is conducting further tests to learn more about the archaea. —Rebecca Carballo, New York Times, 11 Nov. 2023

Cloning is much simpler, and for a long time, many scientists thought the common ancestor of all eukaryotes—the branch of life that includes animals, plants, fungi, slime mold, and everything else besides bacteria and the small, strange archaea—took that route. —Ilana E. Strauss, The Atlantic, 11 Nov. 2020

Word History

Etymology

New Latin, from Greek archaios

First Known Use

1990, in the meaning defined above

Kids Definition

archaea

plural noun

ar·​chaea är-ˈkē-ə 

: single-celled organisms that are prokaryotes often of harsh environments (as hot springs) and include forms that produce methane

Medical Definition

archaea

noun plural

ar·​chaea är-ˈkē-ə 

1

capitalized : a domain of primitive single-celled prokaryotic microorganisms including methane-producing forms and others that thrive in extremely salty or hot, often acidic environments

They are largely Archaea, a domain of life first identified 20 years ago …

—Charles W. Petit and Laura Tangley, U.S. News & World Report

2

: microorganisms of the domain Archaea

Many of the archaea are thermophilic.

—David W. Wolfe, Wilson Quarterly

archaeal

är-ˈkē-əl 

adjective

Despite the morphological resemblance of archaea to bacterial cells (e.g., lack of a nuclear membrane), many archaeal processes, such as transcription, are much more similar to those of eukaryotes.

—Ken F. Jarrell, Bioscience