Crenarchaeota

In taxonomy, the Crenarchaeota (also known as Crenarchaea or eocytes) are a phylum of the Archaea. Initially, the Crenarchaeota were thought to be extremophiles (e.g., thermophilic and psychrophilic organisms) but recent studies have identified them as the most abundant archaea in the marine environment. Originally, they were separated from the other archaea based on rRNA sequences; since then physiological features, such as lack of histones have supported this division. However, some crenarchaea were found to have histones. Until recently all cultured Crenarchaea had been thermophilic or hyperthermophilic organisms, some of which have the ability to grow up to 113 °C. These organisms stain gram negative and are morphologically diverse having rod, cocci, filamentous and oddly shaped cells.

Sulfolobus
One of the best characterized members of the Crenarcheota is Sulfolobus solfataricus. This organism was originally isolated from geothermally-heated sulfuric springs in Italy, and grows at 80 °C and pH of 2-4. Since its initial characterization by Wolfram Zillig, a pioneer in thermophile and archaeon research, similar species in the same genus have been found around the world. Unlike the vast majority of cultured thermophiles, Sulfolobus grows aerobically and chemoorganotrophically (gaining its energy from organic sources such as sugars). These factors allow a much easier growth than anaerobic organisms and have led to Sulfolobus becoming a model organism for the study of hyperthermophiles and a large group of diverse viruses that replicate within them.

Marine species
Beginning in 1992, data were published that reported sequences of genes belonging to the Crenarchaea in marine environments. , Since then analysis of the abundance lipids from the membranes of Crenarchaea taken from the open ocean have been used to determine the concentration of these “low temperature Crenarchaea”. Based on these measurements these organisms are thought to be very abundant and one of the main contributors to the fixation of carbon. DNA sequences from Crenarchaea have also been found in soil and freshwater environments suggesting that this phylum is ubiquitous to most environments.

In 2005, evidence of the first cultured “low temperature Crenarchaea” was published. Named Nitrosopumilus maritimus, it is an ammonia-oxidizing organism isolated from a marine aquarium tank and grown at 28 °C.

Scientific journals