science

Hadesarchaea

Hadesarchaea 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 Hadesarchaea rather than just read about it. In short: Hadesarchaea, formerly called the South-African Gold Mine Miscellaneous Euryarchaeal Group, is a class of thermophile microorganisms that have been found in deep mines, hot springs, marine sediments, and other subterranean environments. Nomenclature These archaea were initially called South-African Gold Mine Miscellaneous Euryarchaeal Group (SAGMEG), after their initial site of discovery.

Key takeaways

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

Reference excerpt

Hadesarchaea, formerly called the South-African Gold Mine Miscellaneous Euryarchaeal Group, is a class of thermophile microorganisms that have been found in deep mines, hot springs, marine sediments, and other subterranean environments.

Nomenclature These archaea were initially called South-African Gold Mine Miscellaneous Euryarchaeal Group (SAGMEG), after their initial site of discovery. The name Hadesarchaea was proposed by Baker et al. in 2016, a reference to the Greek god of the underworld.

Phylogeny Previously, Hadesarchaea (or SAGMEG) were only known to exist through their distinctive phylogenetic position in the tree of life. In 2016, scientists using metagenomic shotgun sequencing were able to assemble several near-full genomes of these archaea. It was shown that the genome of Hadesarchaea is approximately 1.5 Megabase pairs in size, which is about 0.5 Mbp smaller than most archaea. These archaea have not been successfully cultivated in the laboratory, but their metabolic properties have been inferred from the genomic reconstructions. Hadesarchaea may have evolved from a methanogenic ancestor based on the genetic similarity with other methanogenic organisms.

Taxonomy "Persephonarchaeia" corrig. Mwirichia et al. 2016 (MSBL-1) "Hadarchaeia" Chuvochina et al. 2019 ["Hadesarchaea" Baker et al. 2016] (SAGMEG) "Hadarchaeales" Chuvochina et al. 2019 ["Hadesarchaeales" Hua et al. 2019] "Cerberiarchaeaceae" Benito Merino et al. 2024 "Candidatus Cerberiarchaeum" Benito Merino et al. 2024 "Ca. C. oleivorans" Benito Merino et al. 2024 "Candidatus Melinoarchaeum" Yu et al. 2024 "Ca. M. fermentans" Yu et al. 2024 "Hadarchaeaceae" Chuvochina et al. 2019 ["Hadesarchaeaceae" corrig. Hua et al. 2019] "Candidatus Hadarchaeum" Chuvochina et al. 2019 "Ca. H. yellowstonense" Chuvochina et al. 2019 "Candidatus Hadesarchaeum" Hua et al. 2019 "Ca. H. tengchongensis" Hua et al. 2019 "Candidatus Methanourarchaeum" Hua et al. 2019 "Ca. M. thermotelluricum" Hua et al. 2019

Habitat and metabolism These microbes were first discovered in a gold mine in South Africa at a depth of approximately 3 km (2 mi), where they are able to live without oxygen or light. They were later also found in the White Oak River estuary in North Carolina and in Yellowstone National Park's Lower Culex Basin. These areas are approximately 70 °C (158 °F) and highly alkaline. Based on phylogenetic marker gene survey, Hadesarchaeota might be present in soils in ancient mining areas in East Harz region, Germany. The microbes have been found in other marine environments as well. Some of these areas include cold seep systems in the South China Sea. Hadesarchaea has been found to be a dominant member of the archaeal community in the area. These cold seeps contain gas hydrate bearing sediments in which microbes play a major role in biogeochemical cycling. It is believed that Hadesarchaea is involved in the reaction of carbon dioxide with water in this environment. Hadesarchaea have also been found in subseafloor habitats located in the Guaymas Basin and Sonora Margin around the Gulf of California. In addition to being present in marine sediments, mines, and hot springs, Hadesarchaea has been identified in the gut microbiome of certain fish species. The freshwater pufferfish (Tetraodon cutcutia), native to India, Assam, Bihar, and West Bengal, was found to have Hadesarchaea present in their gut microbiome. Hadesarchaea was found to be in the second most abundant in the archaeal community of the freshwater pufferfish. This was found to be similar to community abundance found in the gut of carnivorous Salmon and herbivorous grass carp. While Hadesarchaea are found to be in such high abundance for these environments, it is not completely known how they influence the health and trophic level of these fish. Hadesarchaea are unique among known archaea in that they can convert carbon monoxide and water to carbon dioxide and oxygen, producing hydrogen as a by-product. From metagenome-assembled genome (MAG) data, Hadesarchaea possess genes associated with Wood-Ljungdahl carbon fixation pathway, methanogenesis and alkane metabolism. Hadesarchaeal genomes have also been reported to contain genes that enable them to metabolize sugars and amino acids in a heterotrophic lifestyle, and perform dissimilatory nitrite reduction to ammonium. Initial research suggests that these organisms are also involved in significant geochemical processes. Because of their relatively small genome, it is assumed that the genomes of Hadesarchaea have been subjected to genome streamlining, possibly as a result of nutrient limitation.

See also Archea Microbiology Fermentative hydrogen production Thermophiles Geysers List of Archaea genera

References

Worked examples

Example 1 — a first encounter with Hadesarchaea

Start with the simplest possible case. Write down what Hadesarchaea 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 Hadesarchaea 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 Hadesarchaea 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 Hadesarchaea

In research: Hadesarchaea 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 Hadesarchaea 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: Hadesarchaea is common in secondary-school and first-year university syllabi. It links to neighbouring topics Alkaliphiles, Methanobacteriati, Thermophiles, so understanding it makes those chapters shorter.
In everyday life: Look for Hadesarchaea 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 Hadesarchaea in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Hadesarchaea 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 Hadesarchaea out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Hadesarchaea in simple terms?

Why does Hadesarchaea 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 Hadesarchaea?

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 Hadesarchaea.