Euryarchaeota

Euryarchaeota is a major phylum of the domain Archaea and encompasses a broad and highly diverse group of microorganisms. Its members include classical methanogens, halophiles, and several thermophilic lineages. They occupy a wide range of environments, from anaerobic sediments and the guts of ruminants to hypersaline lakes and oil reservoirs. Like other archaea, euryarchaeotes generally synthesize membrane lipids with ether linkages and often rely on biochemistry distinct from bacteria and eukaryotes.

Ecology and metabolism: Methanogens produce methane as a metabolic end product and are typically strict anaerobes, contributing to the global methane cycle in wetlands, animal guts, and anaerobic digesters. Halophiles within this phylum tolerate and often require high salt concentrations, employing adaptations to maintain cellular stability in saline environments. Other euryarchaeotes include sulfate-reducing archaea and various hyperthermophilic groups that thrive at elevated temperatures. The diversity of energy metabolisms within this phylum makes it one of the most metabolically versatile branches of Archaea.

Taxonomy and research: Euryarchaeota is one of the principal archaeal phyla recognized in current taxonomy, defined largely by phylogenetic analyses of ribosomal RNA genes and genomes. Several model organisms, such as Methanococcus jannaschii and Halobacterium salinarum, have been studied extensively, illuminating archaeal cell biology, biochemistry, and aspects of early evolution. Ongoing genomic and environmental sequencing continues to refine the internal structure and ecological roles of Euryarchaeota.