|
Lokiarchaeota
Lokiarchaeota is a proposed phylum of the Archaea. The phylum includes all members of the group previously named Deep Sea Archaeal Group (DSAG), also known as Marine Benthic Group B (MBG-B). Lokiarchaeota is part of the superphylum Asgard containing the phyla: Lokiarchaeota, Thorarchaeota, Odinarchaeota, Heimdallarchaeota, and Helarchaeota. A phylogenetic analysis disclosed a monophyletic grouping of the Lokiarchaeota with the eukaryotes. The analysis revealed several genes with cell membrane-related functions. The presence of such genes support the hypothesis of an archaeal host for the emergence of the eukaryotes; the eocyte-like scenarios. Lokiarchaeota was introduced in 2015 after the identification of a candidate genome in a metagenomic analysis of a mid-oceanic sediment sample. This analysis suggests the existence of a genus of unicellular life dubbed ''Lokiarchaeum''. The sample was taken near a hydrothermal vent at a vent field known as Loki's Castle located at the ben ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asgard (archaea)
Asgard or Asgardarchaeota is a proposed superphylum consisting of a group of archaea that includes Lokiarchaeota, Thorarchaeota, Odinarchaeota, and Heimdallarchaeota. It appears the eukaryotes emerged within the Asgard, in a branch containing the Heimdallarchaeota. This supports the two-domain system of classification over the three-domain system. Discovery and nomenclature In the summer of 2010, sediments were analysed from a gravity core taken in the rift valley on the Knipovich ridge in the Arctic Ocean, near the Loki's Castle hydrothermal vent site. Specific sediment horizons previously shown to contain high abundances of novel archaeal lineages were subjected to metagenomic analysis. In 2015, an Uppsala University-led team proposed the Lokiarchaeota phylum based on phylogenetic analyses using a set of highly conserved protein-coding genes. Through a reference to the hydrothermal vent complex from which the first genome sample originated, the name refers to Loki, the Nors ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Odinarchaeota
Asgard or Asgardarchaeota is a proposed superphylum consisting of a group of archaea that includes Lokiarchaeota, Thorarchaeota, Odinarchaeota, and Heimdallarchaeota. It appears the eukaryotes emerged within the Asgard, in a branch containing the Heimdallarchaeota. This supports the two-domain system of classification over the three-domain system. Discovery and nomenclature In the summer of 2010, sediments were analysed from a gravity core taken in the rift valley on the Knipovich ridge in the Arctic Ocean, near the Loki's Castle hydrothermal vent site. Specific sediment horizons previously shown to contain high abundances of novel archaeal lineages were subjected to metagenomic analysis. In 2015, an Uppsala University-led team proposed the Lokiarchaeota phylum based on phylogenetic analyses using a set of highly conserved protein-coding genes. Through a reference to the hydrothermal vent complex from which the first genome sample originated, the name refers to Loki, the Nors ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heimdallarchaeota
Asgard or Asgardarchaeota is a proposed superphylum consisting of a group of archaea that includes Lokiarchaeota, Thorarchaeota, Odinarchaeota, and Heimdallarchaeota. It appears the eukaryotes emerged within the Asgard, in a branch containing the Heimdallarchaeota. This supports the two-domain system of classification over the three-domain system. Discovery and nomenclature In the summer of 2010, sediments were analysed from a gravity core taken in the rift valley on the Knipovich ridge in the Arctic Ocean, near the Loki's Castle hydrothermal vent site. Specific sediment horizons previously shown to contain high abundances of novel archaeal lineages were subjected to metagenomic analysis. In 2015, an Uppsala University-led team proposed the Lokiarchaeota phylum based on phylogenetic analyses using a set of highly conserved protein-coding genes. Through a reference to the hydrothermal vent complex from which the first genome sample originated, the name refers to Loki, the Nors ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Archaea
Archaea ( ; singular archaeon ) is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes. Archaea were initially classified as bacteria, receiving the name archaebacteria (in the Archaebacteria kingdom), but this term has fallen out of use. Archaeal cells have unique properties separating them from the other two domains, Bacteria and Eukaryota. Archaea are further divided into multiple recognized phyla. Classification is difficult because most have not been isolated in a laboratory and have been detected only by their gene sequences in environmental samples. Archaea and bacteria are generally similar in size and shape, although a few archaea have very different shapes, such as the flat, square cells of ''Haloquadratum walsbyi''. Despite this morphological similarity to bacteria, archaea possess genes and several metabolic pathways that are more closely related to those of eukaryotes, notably for the enzymes involved ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Archaea
Archaea ( ; singular archaeon ) is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes. Archaea were initially classified as bacteria, receiving the name archaebacteria (in the Archaebacteria kingdom), but this term has fallen out of use. Archaeal cells have unique properties separating them from the other two domains, Bacteria and Eukaryota. Archaea are further divided into multiple recognized phyla. Classification is difficult because most have not been isolated in a laboratory and have been detected only by their gene sequences in environmental samples. Archaea and bacteria are generally similar in size and shape, although a few archaea have very different shapes, such as the flat, square cells of ''Haloquadratum walsbyi''. Despite this morphological similarity to bacteria, archaea possess genes and several metabolic pathways that are more closely related to those of eukaryotes, notably for the enzymes involved ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eocyte Hypothesis
The eocyte hypothesis in evolutionary biology proposes the origin of eukaryotes from a group of prokaryotes called eocytes (later classified as Thermoproteota, a group of archaea). After his team at the University of California, Los Angeles discovered eocytes in 1984, James A. Lake formulated the hypothesis as "eocyte tree" that proposed eukaryotes as part of archaea. Lake hypothesised the Tree of life (biology), tree of life as having only two primary branches: Parkaryoates that include Bacteria and Archaea, and karyotes that comprise Eukaryotes and eocytes. Parts of this early hypothesis were revived in a newer two-domain system of biological classification which named the primary domains as Archaea and Bacteria. Lake's hypothesis was based on an analysis of the structural components of ribosomes. It was largely ignored, being overshadowed by the three-domain system which relied on more precise genetic analysis. In 1990, Carl Woese and his colleagues proposed that cellular life ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Loki's Castle
Loki's Castle is a field of five active hydrothermal vents in the mid-Atlantic Ocean, located at 73 degrees north on the Mid-Atlantic Ridge between Greenland and Norway at a depth of . The vents were discovered in mid-July 2008 and are the most northerly black smokers to date. They are of geological interest as they occur in a relatively stable region of the Earth's crust, one with diminished tectonic forces and consequently fewer hydrothermal vents. Discovery The vents were discovered by a 25-person multinational scientific expedition of the University of Bergen, Norway, more than north of what were previously the northernmost known, discovered in 2005. The 2005 and 2008 expeditions were both led by geologist Rolf Pedersen of the university's Centre for Geobiology, aboard the research vessel ''G.O. Sars'' (named after the Norwegian marine biologist Georg Ossian Sars and launched in May 2003). The vents were located using a remotely controlled undersea vehicle. Activity The fi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Proteoarchaeota
"Proteoarchaeota" are a proposed archaeal kingdom thought to be closely related to the Eukaryotes.Approximately the same group is sometimes referred to as TACK after the initial letters of its early-found daughter clades: Thaumarchaeota (now Nitrososphaerota), "Aigarchaeota", Crenarchaeota (now Thermoproteota), and "Korarchaeota". Because of the unsettled phylogeny A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological spec ... of the group, the names "Proteoarchaeota" and TACK may become distinct after further re-organization. Classification The phylogenetic relationship of this group is still under discussion. The relationship of the members is approximately as follows: Notes References Archaea Kingdoms (biology) {{Archaea-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thorarchaeota
"''Candidatus'' Thorarchaeota", or simply Thorarchaeota, is a phylum within the superphylum Asgard archaea. The Asgard superphylum represents the closest prokaryotic relatives of eukaryotes. Since there is such a close relation between the two different domains, it provides further evidence to the two-domain tree of life theory which states that eukaryotes branched from the archaeal domain. Asgard archaea are single cell marine microbes that contain branch like appendages and have genes that are similar to eukarya. The asgard archaea superphylum is composed of Thorarchaeota, Lokiarchaeota, Odinarchaeota, and Heimdallarchaeota. Thorarchaeota were first identified from the sulfate-methane transition zone in tidewater sediments. Thorarcheota are widely distributed in marine and freshwater sediments. Discovery Thorarchaeota were discovered by analyzing estuary sediments obtained from the White Oak River in North Carolina. Estuaries are brackish bodies of water where fresh and mar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eukaryote
Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacteria and Archaea (both prokaryotes) make up the other two domains. The eukaryotes are usually now regarded as having emerged in the Archaea or as a sister of the Asgard archaea. This implies that there are only two domains of life, Bacteria and Archaea, with eukaryotes incorporated among archaea. Eukaryotes represent a small minority of the number of organisms, but, due to their generally much larger size, their collective global biomass is estimated to be about equal to that of prokaryotes. Eukaryotes emerged approximately 2.3–1.8 billion years ago, during the Proterozoic eon, likely as flagellated phagotrophs. Their name comes from the Greek εὖ (''eu'', "well" or "good") and κάρυον (''karyon'', "nut" or "kernel"). Euka ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eukaryotic
Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacteria and Archaea (both prokaryotes) make up the other two domains. The eukaryotes are usually now regarded as having emerged in the Archaea or as a sister of the Asgard archaea. This implies that there are only two domains of life, Bacteria and Archaea, with eukaryotes incorporated among archaea. Eukaryotes represent a small minority of the number of organisms, but, due to their generally much larger size, their collective global biomass is estimated to be about equal to that of prokaryotes. Eukaryotes emerged approximately 2.3–1.8 billion years ago, during the Proterozoic eon, likely as flagellated phagotrophs. Their name comes from the Greek εὖ (''eu'', "well" or "good") and κάρυον (''karyon'', "nut" or "kernel"). Euka ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Monophyletic
In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic groups are typically characterised by shared derived characteristics ( synapomorphies), which distinguish organisms in the clade from other organisms. An equivalent term is holophyly. The word "mono-phyly" means "one-tribe" in Greek. Monophyly is contrasted with paraphyly and polyphyly as shown in the second diagram. A ''paraphyletic group'' consists of all of the descendants of a common ancestor minus one or more monophyletic groups. A '' polyphyletic group'' is characterized by convergent features or habits of scientific interest (for example, night-active primates, fruit trees, aquatic insects). The features by which a polyphyletic group is differentiated from others are not inherited from a common ancestor. These definitions have tak ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
.jpg "Click for more on -> Archaea")
