science

Korarchaeia

Korarchaeia is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Korarchaeia rather than just read about it. In short: "Candidatus Korarchaeia" is a class of Archaea under the phylum Thermoproteota. The name is derived from the Greek noun koros or kore, meaning "young man" or "young woman", and the Greek adjective archaios which means "ancient".

Key takeaways

Korarchaeia belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Korarchaeia to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Korarchaeia from memory before moving on to harder problems.

Reference excerpt

"Candidatus Korarchaeia" is a class of Archaea under the phylum Thermoproteota. The name is derived from the Greek noun koros or kore, meaning "young man" or "young woman", and the Greek adjective archaios which means "ancient". It was previously designated as phylum Korarchaeota and as kingdom with various names like Crenarchaeida or Proteoarchaeota.

Taxonomy "Candidatus Korarchaeia" had been designated as Korarchaeota in the domain, Archaea. They are thought to have diverged relatively early in the genesis of Archaea and are among the deep-branching lineages. They have been classified as phylum (and sometimes as kingdom) Korarchaeota, along with Thaumarchaeota, Aigarchaeota, Crenarchaeota, under the kingdom Thermoproteati. The evolutionary link between Promethearchaeati and Thermoproteati. The first member of "Candidatus Korarchaeia" to have its genome reconstructed was Korarchaeum cryptofilum, which was found in a hot spring, Obsidian Pool, in Yellowstone National Park and described in 2008. Since then only a few Korarchaeal genomes have been described. To check for "Candidatus Korarchaeia", samples from a variety of hot springs in Iceland and Kamchatka were gathered. According to the samples and analysis, the Icelandic samples contained about 87 distinct 16S ribosomal nucleic acid sequences, whereas the Kamchatkan samples contained about 33. Based on protein sequences and phylogenetic analysis of conserved single genes, the "Candidatus Korarchaeia" was identified as a "deep archaeal lineage" with a possible relationship to the Crenarchaeota. Furthermore, given the known genetic makeup of archaea, the "Candidatus Korarchaeia" may have preserved a set of biological traits that correspond to the earliest known archaeal form. Analysis of their 16S rRNA gene sequences suggests that they are a deeply branching lineage that does not belong to the main archaeal groups, Thermoproteota and Euryarchaeota. Analysis of the genome of one "Candidatus Korarchaeia" that was enriched from a mixed culture revealed a number of both Crenarchaeota- and Euryarchaeota-like features and supports the hypothesis of a deep-branching ancestry.

Revision In 2001, George M. Garrity and John G. Holt described the phylum Crenarchaeota to include a single class Thermoprotei. With the growing number of prokaryotic taxa and the inconsistent nomenclature and classification, there was a need to revise the overall classification of archaea. In 2014, French taxonomists led by David Moreira designated "TACK", generally considered as a superphylum, into a single kingdom named Proteoarchaeota. However, such revision was not valid under the rules of the International Committee on Systematics of Prokaryotes (ICSP). In 2021, a team of Australian scientists led by Christian Rinke and Philip Hugenholtz published a new classification on archaea in which their genetic evidence indicated Thermoproteati archaea belong to a unified phylum Thermoproteota, which could be divided into the classes "Candidatus Korarchaeia", Thermoprotei, Methanomethylicia (former phylum Ca. Verstraetearchaeota), Bathyarchaeia and Nitrososphaeria (former phylum Ca. Thaumachaeota). The List of Prokaryotic names with Standing in Nomenclature (LPSN), an authority on maintenance and cataloguing prokaryotic taxons, upheld this classification of "Candidatus Korarchaeia" as a "preferred name" as a class. In 2022, the ICSP revised its International Code of Nomenclature of Prokaryotes (ICNP, Prokaryotic Code). Following the revised code, Markus Göker and Aharon Oren (leaders of the ICSP), revised the domain and kingdom classifications 2024 in which the traditionally named "TACK" group was renamed to kingdom Thermoproteati. In this way, previous designations such as phylum Korarchaeota or kingdom Proteoarchaeota are invalidated.

Species The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) and National Center for Biotechnology Information (NCBI).

Listed below are the known species of "Candidatus Korarchaeia":

Order Korarchaeales Petitjean et al. 2015 Family Korarchaeaceae Rinke et al. 2020 Genus "Candidatus Korarchaeum" Elkins et al. 2008 Species "Ca. Korarchaeum cryptofilum" Elkins et al. 2008 "Ca. Korarchaeum cryptofilum" OPF8 Genus "Ca. Methanodesulfokores" corrig. McKay et al. 2019 Species "Ca. Methanodesulfokores washburnensis" corrig. McKay et al. 2019 Genus "Ca. Korarchaeota" Genus "Ca. Korarchaeota archaeon" NZ13-K Genus Korarchaeote SRI-306 Genus environmental samples uncultured korarchaeote pBA5 uncultured korarchaeote pJP27 uncultured korarchaeote pJP78

Reference species A strain of Korarchaeum cryptofilum was cultivated from an enrichment culture from a hot spring in Yellowstone National Park, USA and described in 2008. The cells are long and needle-shaped, which gave the species its name, alluding to its "cryptical filaments". This organism lacks the genes for purine nucleotide biosynthesis and thus relies on environmental sources to meet its purine requirements.

Characteristics "Candidatus Korarchaeia" exhibit characteristics such as having a cell wall without peptidoglycan, as well as lipid membranes that are ether-linked. They have a surface layer of paracrystalline protein. This surface layer, known as the S-layer, is densely packed and consists of 1-2 proteins form various lattice structures and are most likely what maintains the cells' structural integrity. They are typically rod-shaped, however, it has been found that this morphology can change to be thicker-shaped in the presence of higher sodium dodecyl sulfate (SDS) concentrations. The cells have an ultrathin filamentous morphology that may vary in length. They typically average 15 μm in length and 0.16 μm in diameter but can be seen up to 100 μm long. Some Archaea can fix carbon dioxide through the 3-hydroxypropionate/4-hydroxybutyrate pathway into organic compounds

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Korarchaeia

Start with the simplest possible case. Write down what Korarchaeia claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Korarchaeia before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Korarchaeia ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Korarchaeia

In research: Korarchaeia appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Korarchaeia in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Korarchaeia is common in secondary-school and first-year university syllabi. It links to neighbouring topics Archaea phyla, Candidatus taxa, so understanding it makes those chapters shorter.
In everyday life: Look for Korarchaeia outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Korarchaeia in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Korarchaeia means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Korarchaeia out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Korarchaeia in simple terms?

Why does Korarchaeia matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Korarchaeia?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Korarchaeia.