Crenarchaeota
Encyclopedia
In taxonomy
, the Crenarchaeota (Greek for "spring old quality") (also known as Crenarchaea or eocytes) has been classified as either a phylum of the Archaea
kingdom or a kingdom
of its own. Initially, the Crenarchaeota were thought to be extremophile
s (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 histone
s 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 at up to 113 °C. These organisms stain Gram negative and are morphologically diverse having rod, cocci, filamentous
and oddly shaped cells.
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 archaean research, similar species in the same genus
have been found around the world. Unlike the vast majority of cultured thermophiles, Sulfolobus
grows aerobically
and chemoorganotroph
ically (gaining its energy from organic sources such as sugars). These factors allow a much easier growth under laboratory conditions than anaerobic organism
s 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.
s from the membranes of Crenarchaea taken from the open ocean have been used to determine the concentration of these “low temperature Crenarchaea” (See TEX-86
). Based on these measurements of their signature lipids, Crenarchaea 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.
Alpha taxonomy
Alpha taxonomy is the discipline concerned with finding, describing and naming species of living or fossil organisms. This field is supported by institutions holding collections of these organisms, with relevant data, carefully curated: such institutes include natural history museums, herbaria and...
, the Crenarchaeota (Greek for "spring old quality") (also known as Crenarchaea or eocytes) has been classified as either a phylum of the Archaea
Archaea
The Archaea are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon...
kingdom or a kingdom
Kingdom (biology)
In biology, kingdom is a taxonomic rank, which is either the highest rank or in the more recent three-domain system, the rank below domain. Kingdoms are divided into smaller groups called phyla or divisions in botany...
of its own. Initially, the Crenarchaeota were thought to be extremophile
Extremophile
An extremophile is an organism that thrives in physically or geochemically extreme conditions that are detrimental to most life on Earth. In contrast, organisms that live in more moderate environments may be termed mesophiles or neutrophiles...
s (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 histone
Histone
In biology, histones are highly alkaline proteins found in eukaryotic cell nuclei that package and order the DNA into structural units called nucleosomes. They are the chief protein components of chromatin, acting as spools around which DNA winds, and play a role in gene regulation...
s 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 at up to 113 °C. These organisms stain Gram negative and are morphologically diverse having rod, cocci, filamentous
Filamentation
Filamentation is the anomalous growth of certain bacteria, such as E. coli, in which cells continue to elongate but do not divide . Bacterial filamentation is often observed as a result of bacteria responding to various stresses, including DNA damage or inhibition of replication...
and oddly shaped cells.
Sulfolobus
One of the best characterized members of the Crenarcheota is Sulfolobus solfataricus. This organism was originally isolated from geothermally-heatedHot Springs
Hot Springs may refer to:* Hot Springs, Arkansas** Hot Springs National Park, Arkansas*Hot Springs, California**Hot Springs, Lassen County, California**Hot Springs, Modoc County, California**Hot Springs, Placer County, California...
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 archaean research, similar species in the same genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
have been found around the world. Unlike the vast majority of cultured thermophiles, Sulfolobus
Sulfolobus
Sulfolobus is a genus of microorganism in the family Sulfolobaceae. It belongs to the archea domain.Sulfolobus species grow in volcanic springs with optimal growth occurring at pH 2-3 and temperatures of 75-80 °C, making them acidophiles and thermophiles respectively...
grows aerobically
Aerobic organism
An aerobic organism or aerobe is an organism that can survive and grow in an oxygenated environment.Faculitative anaerobes grow and survive in an oxygenated environment and so do aerotolerant anaerobes.-Glucose:...
and chemoorganotroph
Chemoorganotroph
Chemoorganotrophs are organisms which use organic compounds as their energy source. These organic chemicals include glucose and acetate. All animals are chemoorganotrophs, as are fungi, protozoa, and some bacteria. Indeed, most heterotrophs are chemoorganotrophs. However, chemolithotrophs instead...
ically (gaining its energy from organic sources such as sugars). These factors allow a much easier growth under laboratory conditions than anaerobic organism
Anaerobic organism
An anaerobic organism or anaerobe is any organism that does not require oxygen for growth. It could possibly react negatively and may even die if oxygen is present...
s 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 abundant lipidLipid
Lipids constitute a broad group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins , monoglycerides, diglycerides, triglycerides, phospholipids, and others...
s from the membranes of Crenarchaea taken from the open ocean have been used to determine the concentration of these “low temperature Crenarchaea” (See TEX-86
TEX-86
TEX86 is a paleothermometer based on the composition of membrane lipids of the marine picoplankton Crenarchaeota.Wuchter et al. found that the number of cyclopentane rings in Crenarchaeota membrane lipids changes linearly with temperature in order to regulate membrane fluidity...
). Based on these measurements of their signature lipids, Crenarchaea are thought to be very abundant and one of the main contributors to the fixation of carbon
Carbon fixation
In biology, carbon fixation is the reduction of carbon dioxide to organic compounds by living organisms. The obvious example is photosynthesis. Carbon fixation requires both a source of energy such as sunlight, and an electron donor such as water. All life depends on fixed carbon. Organisms that...
. 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
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
-oxidizing organism isolated from a marine aquarium tank and grown at 28°C.
Eocyte hypothesis
The eocyte hypothesis proposed in the 1980s by James Lake suggests that eukaryotes evolved from the prokaryotic eocyte.External links
- Crenarchaeota from the University of Wisconsin Virtual Microbiology site.
- Comparative Analysis of Crenarchaeal Genomes (at DOE'sUnited States Department of EnergyThe United States Department of Energy is a Cabinet-level department of the United States government concerned with the United States' policies regarding energy and safety in handling nuclear material...
IMG systemIntegrated Microbial Genomes SystemThe Integrated Microbial Genomes is a genome browsing and annotation system developed by the DOE-Joint Genome Institute. IMG contains all the draft and complete microbial genomes sequenced by the DOE-JGI integrated with other publicly available genomes...
)