Crenarchaeal

Crenarchaeal refers to things related to the crenarchaeal lineage of archaea, typically the group once classified as the phylum Crenarchaeota. Members of this group are diverse in metabolism and ecology but are commonly associated with high-temperature, acidic, or otherwise extreme environments. The term is used to describe both organisms and features linked to this lineage.

Taxonomy and classification have shifted in modern systems. Traditionally, Crenarchaeota was a major archaeal phylum containing several thermophilic and acidophilic lineages. In some contemporary classifications, descendants of crenarchaeal groups are placed in the broader phylum Thermoproteota, and taxonomic schemes continue to evolve as new genomic data emerge. Nevertheless, crenarchaeal remains a useful label for organisms of the original crenarchaeal lineage and for describing shared molecular characteristics.

Key characteristics of crenarchaeal organisms include cellular diversity, typically lacking peptidoglycan in their cell walls and possessing archaeal ether lipids in their membranes. Cell shapes range from cocci and rods to irregular filaments. Many crenarchaeota are extremophiles and chemolithoautotrophs or chemoorganotrophs, often utilizing reduced sulfur compounds or hydrogen as energy sources. Autotrophic crenarchaeotes frequently use carbon fixation pathways such as the 3-hydroxypropionate/4-hydroxybutyrate cycle.

Ecologically, crenarchaeal lineages are common in hot springs, volcanic and hydrothermal environments, acidic habitats, and other extreme niches. They play roles in elemental cycles, notably sulfur cycling, and contribute to primary production in some extreme ecosystems.

See also: Archaea, Crenarchaeota, Thermoproteota.