Crenarchaeota

Crenarchaeota is a phylum within the domain Archaea. It has long been recognized as one of the main archaeal lineages and is composed of a diverse group of organisms that are frequently associated with high-temperature, sulfur-rich environments, such as hot springs, volcanic vents, and hydrothermal systems. Members of this phylum display a variety of metabolic strategies, including chemolithoautotrophy and chemoorganoheterotrophy, with many species capable of using reduced sulfur compounds or hydrogen as electron donors and carbon dioxide or organic carbon as carbon sources.

Taxonomy and classification: Traditional classifications place several orders within Crenarchaeota, notably Thermoproteales, Desulfurococcales, and Sulfolobales. In newer phylogenetic frameworks, some lineages previously assigned to Crenarchaeota have been moved to other phyla as taxonomic understanding has evolved; for example, ammonia-oxidizing archaea previously grouped with Crenarchaeota are now placed in Thaumarchaeota. Despite these changes, Crenarchaeota remains a reference term for a broad assemblage of thermoacidophilic and hyperthermophilic archaea.

Morphology and ecology: Crenarchaeotes range from irregular cocci to filamentous shapes. Their cell envelopes often include an S-layer. Many species are acidophilic and thermophilic, thriving in extreme temperatures and pH conditions, though the group also encompasses lineages with less extreme preferences. Ecologically, they contribute to sulfur and carbon cycling in extreme environments, including sulfur-oxidizing and hydrogenotrophic members.

Genomics and evolution: Crenarchaeota share the distinctive genetic and biochemical features that characterize Archaea, providing insight into archaeal diversity and evolution. Studying this group helps illuminate how life adapts to extreme habitats and how archaeal metabolism has diversified over time.