eeltuumsed organismid, kes eristusid bakteritest ja eukarüootidest väga varasel evolutsioonietapil ning on veekogudes tihti levinud äärmuslikes elukeskkondades, an ancient group of microbes that diverged from bacteria billions of years ago, microbes such asmethane producers, extreme halophiles, and certainthermophiles that are now classified as a separatekingdom, making them one of three major divisions oflife forms: archaea, bacteria, and eukaryotes