In taxonomy, the Crenarchaeota (Greek for "spring old quality") (also known as Crenarchaea or eocytes) are a phylum of the Archaea.^[1] Initially, the Crenarchaeota were thought to be extremophiles (e.g. living in primarily extreme hot or cold environments) but recent studies have identified them as the most abundant archaea in the marine environment.^[2] Until recently all cultured Crenarchaea had been high heat-thriving organisms, some of which have the ability to grow at up to 113 °C.^[3] These organisms stain gram negative and are morphologically diverse having rod, cocci, filamentous and oddly shaped cells.^[4]

Photo: Archaea Sulfolobus infected with specific virus STSV-1.