archeák

Archaea, commonly referred to in Czech as archeák, are a domain of single-celled microorganisms that resemble bacteria in being prokaryotic, yet are genetically and biochemically distinct. They form one of the three cellular domains of life—Archaea, Bacteria, and Eukarya—defined largely by ribosomal RNA sequences identified by Carl Woese and colleagues in 1977. Archaea inhabit a broad range of environments, from oceans and soils to extreme settings such as hot springs, saline lakes, and the guts of animals.

Cell biology: Archaea lack a nucleus and membrane-bound organelles, but their membrane lipids are ether-linked and their cell walls often lack peptidoglycan, sometimes containing pseudopeptidoglycan. Their transcription and translation machinery share features with eukaryotes, and some archaea possess histone-like proteins that organize DNA.

Metabolism and diversity: Archaea display diverse metabolisms. Methanogens produce methane in anaerobic environments; halophiles tolerate high salt; thermophiles and acidophiles thrive at extreme temperatures and pH. Many archaea are chemolitho- or chemoorganoheterotrophs, and numerous lineages are symbionts in animals and plants.

Ecology and applications: They play key roles in carbon and nitrogen cycles and are important in anaerobic digestion and soil ecosystems. In biotechnology, archaeal enzymes—such as thermostable DNA polymerases—are widely used in molecular biology.

Taxonomy and evolution: Modern classification places archaea in multiple phyla, including Euryarchaeota, Crenarchaeota, Thaumarchaeota, and others. Phylogenetic analyses show that Archaea are more closely related to eukaryotes in some cellular processes, highlighting their distinct evolutionary path from bacteria.