# Fervicoccales
Fervidicoccales, formally published as Fervidicoccales Perevalova et al. 2010, is an order of extremely thermophilic, obligately anaerobic, organotrophic archaea of the phylum Crenarchaeota ([Thermoproteota](https://www.edgepedia.org/thermoproteota)). It contains a single family, Fervidicoccaceae, a single genus, Fervidicoccus, and a single validly published species, Fervidicoccus fontis, isolated from terrestrial hot springs in the Uzon caldera on the [Kamchatka](https://www.edgepedia.org/kamchatka) peninsula.[1](https://www.microbiologyresearch.org/content/journal/ijsem/10.1099/ijs.0.019042-0) • [2](https://lpsn.dsmz.de/genus/fervidicoccus) The order matters to archaeal systematics because its 16S rRNA sequence is no more than 89% identical to any other cultured member of the class Thermoprotei, making it an independent lineage adjacent to the orders [Desulfurococcales](https://www.edgepedia.org/desulfurococcales) and Acidilobales.[1](https://www.microbiologyresearch.org/content/journal/ijsem/10.1099/ijs.0.019042-0)
| Key fact | Detail |
|---|---|
| Formal name and authorship | Fervidicoccales Perevalova et al. 2010, validly published under the ICNP; taxonomic status "correct name"[3](https://lpsn.dsmz.de/order/fervidicoccales) |
| Composition | One family (Fervidicoccaceae), one genus (Fervidicoccus), one validly published species (F. fontis)[2](https://lpsn.dsmz.de/genus/fervidicoccus) |
| Type strain | Kam940T (=DSM 19380T =VKM B-2539T), from hot springs of the Uzon caldera, Kamchatka[1](https://www.microbiologyresearch.org/content/journal/ijsem/10.1099/ijs.0.019042-0) • [4](https://bacdive.dsmz.de/strain/17820) |
| Growth conditions | 55–85 °C (optimum 65–70 °C, doubling time 6.1 h); pH 4.5–7.5 (optimum 5.5–6.0)[1](https://www.microbiologyresearch.org/content/journal/ijsem/10.1099/ijs.0.019042-0) |
| Genome | Small ~1.3-Mb circular chromosome (CP003423) with 1385 protein genes and 45 RNA genes; G+C content 37 mol%[5](https://www.kegg.jp/kegg-bin/show_organism?org=T01936) • [1](https://www.microbiologyresearch.org/content/journal/ijsem/10.1099/ijs.0.019042-0) |
| Cultured diversity | F. fontis is the only cultured representative of the order[6](https://doi.org/10.1002/9781118960608.obm00126) |
| Environmental detection | 16S rRNA genes found in hot springs of Yellowstone, Iceland, New Zealand, Kamchatka, and the Kuril Islands at 55–84 °C[6](https://doi.org/10.1002/9781118960608.obm00126) |
## Taxonomy and nomenclature
The order, family, genus, and species were all validated in a single 2010 publication in the [International Journal of Systematic and Evolutionary Microbiology](https://www.edgepedia.org/international-journal-of-systematic-and-evolutionary-microbiology) (volume 60, pages 2082–2088) by Perevalova and colleagues.[1](https://www.microbiologyresearch.org/content/journal/ijsem/10.1099/ijs.0.019042-0) The LPSN, the official nomenclatural record of the DSMZ, lists Fervidicoccales as validly published under the [International Code of Nomenclature of Prokaryotes](https://www.edgepedia.org/international-code-of-nomenclature-of-prokaryotes) (ICNP) with the taxonomic status of correct name.[3](https://lpsn.dsmz.de/order/fervidicoccales) The SeqCode Registry likewise records the name as Valid (ICNP), ranked as an order within Archaea > Thermoproteota > Thermoprotei, with Fervidicoccaceae as its only child taxon.[7](https://registry.seqco.de/names/7502) The genus Fervidicoccus is the nomenclatural type of both the family and the order, and contains exactly one validly published child taxon, Fervidicoccus fontis Perevalova et al. 2010.[2](https://lpsn.dsmz.de/genus/fervidicoccus)
Genome-based taxonomy disagrees with this placement. The Genome Taxonomy Database (GTDB), version v220, does not recognize Fervidicoccales as a separate order; it recovers the group as o__[Sulfolobales](https://www.edgepedia.org/sulfolobales) within the class Thermoprotei_A, while LPSN (last updated February 2025) continues to list Fervidicoccales as a correct name under Thermoproteota.[6](https://doi.org/10.1002/9781118960608.obm00126) This disagreement between the ICNP-based and genome-based taxonomies remains unresolved.
## Discovery and known members
Two strains, Kam940T and Kam1507b, which shared 99% 16S rRNA gene sequence identity, were isolated from terrestrial hot springs of the Uzon caldera on the Kamchatka peninsula.[1](https://www.microbiologyresearch.org/content/journal/ijsem/10.1099/ijs.0.019042-0) The type strain, Kam940, was isolated from sediment and water of hot springs in the East Thermal Field of the caldera; its complete genome assembly is GCA_000258425 and its 16S rRNA sequence (1269 bp) is EF552404.[4](https://bacdive.dsmz.de/strain/17820) Kam940T was designated the type strain of Fervidicoccus fontis (=DSM 19380T =VKM B-2539T).[1](https://www.microbiologyresearch.org/content/journal/ijsem/10.1099/ijs.0.019042-0) F. fontis remains the only cultured representative of the order and of the family.[6](https://doi.org/10.1002/9781118960608.obm00126) • [8](https://doi.org/10.1002/9781118960608.fbm00268)
## Physiology and habitat
Fervidicoccales are extremely thermophilic, obligately anaerobic, organotrophic microorganisms.[6](https://doi.org/10.1002/9781118960608.obm00126) The type strain grows between 55 and 85 °C, with an optimum at 65–70 °C and a doubling time of 6.1 hours, and between pH 4.5 and 7.5, with optimum growth at pH 5.5–6.0.[1](https://www.microbiologyresearch.org/content/journal/ijsem/10.1099/ijs.0.019042-0) [Metabolism](https://www.edgepedia.org/metabolism) rests on a narrow substrate spectrum: beef extract, gelatin, peptone, pyruvate, sucrose, and yeast extract. Sulfate, sulfite, thiosulfate, and nitrate did not stimulate growth, and 100% H₂ inhibited growth on peptone, so no electron acceptor tested enhanced cultivation.[1](https://www.microbiologyresearch.org/content/journal/ijsem/10.1099/ijs.0.019042-0) Bergey's Manual summarizes the organism as an anaerobic organotroph growing optimally on peptides at 65–70 °C and pH 6.0.[8](https://doi.org/10.1002/9781118960608.fbm00268)
Beyond the two Kamchatkan isolates, 16S rRNA genes belonging to the order have been detected in terrestrial hot springs of [Yellowstone National Park](https://www.edgepedia.org/yellowstone-national-park), Iceland, New Zealand, Kamchatka, and the [Kuril Islands](https://www.edgepedia.org/kuril-islands) (Russia), at temperatures of 55–84 °C and neutral or slightly acidic pH.[6](https://doi.org/10.1002/9781118960608.obm00126) The closest known relatives of the isolates are uncultured clones from hot springs in Yellowstone and Iceland.[1](https://www.microbiologyresearch.org/content/journal/ijsem/10.1099/ijs.0.019042-0)
## Genome and molecular features
The complete circular chromosome of F. fontis Kam940T (GenBank CP003423) encodes 1385 protein genes and 45 RNA genes.[5](https://www.kegg.jp/kegg-bin/show_organism?org=T01936) The genome is small, about 1.3 Mb, and its G+C content is 37 mol%.[9](https://www.academia.edu/144679123/Fervidicoccus_fontis_gen_nov_sp_nov_an_anaerobic_thermophilic_crenarchaeote_from_terrestrial_hot_springs_and_proposal_of_Fervidicoccaceae_fam_nov_and_Fervidicoccales_ord_nov) • [1](https://www.microbiologyresearch.org/content/journal/ijsem/10.1099/ijs.0.019042-0)
The gene content matches the peptide-based physiology. The genome encodes several extracellular proteases and no other extracellular hydrolases, and no complete pathways of carbohydrate catabolism were found, despite sucrose supporting growth.[9](https://www.academia.edu/144679123/Fervidicoccus_fontis_gen_nov_sp_nov_an_anaerobic_thermophilic_crenarchaeote_from_terrestrial_hot_springs_and_proposal_of_Fervidicoccaceae_fam_nov_and_Fervidicoccales_ord_nov) Two [NiFe]-hydrogenases are encoded: a membrane-bound energy-converting hydrogenase and a cytoplasmic one.[9](https://www.academia.edu/144679123/Fervidicoccus_fontis_gen_nov_sp_nov_an_anaerobic_thermophilic_crenarchaeote_from_terrestrial_hot_springs_and_proposal_of_Fervidicoccaceae_fam_nov_and_Fervidicoccales_ord_nov) Certain genomic features of F. fontis correlate with its adaptation to temperatures of 60–80 °C.[6](https://doi.org/10.1002/9781118960608.obm00126)
## Comparison with other crenarchaeal orders
Within the class Thermoprotei, Fervidicoccales stands apart on both sequence and physiology. 16S rRNA analysis showed the isolates to be no more than 89% identical to any cultured member of the class, forming an independent lineage adjacent to the orders Desulfurococcales and Acidilobales.[1](https://www.microbiologyresearch.org/content/journal/ijsem/10.1099/ijs.0.019042-0) Phylogenetic markers and the distribution of blastp hits support this distinct position as a separate lineage adjoining Desulfurococcales.[6](https://doi.org/10.1002/9781118960608.obm00126) Physiologically, the genomic features of F. fontis point to adaptation to 60–80 °C, which is lower than the temperatures preferred by Desulfurococcales.[6](https://doi.org/10.1002/9781118960608.obm00126) Its pH optimum of 5.5–6.0 also places it among the slightly acidophilic rather than strongly acidophilic hot-spring archaea, consistent with growth at pH 4.5–7.5.[1](https://www.microbiologyresearch.org/content/journal/ijsem/10.1099/ijs.0.019042-0)
## Recent developments
No new validly published Fervidicoccales species have appeared since the 2010 description of F. fontis; the genus still contains one validly published child taxon.[2](https://lpsn.dsmz.de/genus/fervidicoccus) What has shifted is classification in genome-based systems: GTDB version v220 recovers the group as o__Sulfolobales within class Thermoprotei_A rather than as its own order, while the LPSN reaffirmed Fervidicoccales as a correct name in its February 2025 update.[6](https://doi.org/10.1002/9781118960608.obm00126) • [3](https://lpsn.dsmz.de/order/fervidicoccales)
## References
1. [Fervidicoccus fontis gen. nov., sp. nov., an anaerobic, thermophilic crenarchaeote from terrestrial hot springs, and proposal of Fervidicoccaceae fam. nov. and Fervidicoccales ord. nov. (IJSEM, 2010)](https://www.microbiologyresearch.org/content/journal/ijsem/10.1099/ijs.0.019042-0)
2. [Genus: Fervidicoccus (LPSN)](https://lpsn.dsmz.de/genus/fervidicoccus)
3. [Order: Fervidicoccales (LPSN)](https://lpsn.dsmz.de/order/fervidicoccales)
4. [Fervidicoccus fontis Kam940 | Type strain | BacDiveID:17820](https://bacdive.dsmz.de/strain/17820)
5. [KEGG GENOME: Fervidicoccus fontis](https://www.kegg.jp/kegg-bin/show_organism?org=T01936)
6. [Fervidicoccales (Bergey's Manual of Systematics of Archaea and Bacteria)](https://doi.org/10.1002/9781118960608.obm00126)
7. [Fervidicoccales | SeqCode Registry](https://registry.seqco.de/names/7502)
8. [Fervidicoccaceae (Bergey's Manual of Systematics of Archaea and Bacteria)](https://doi.org/10.1002/9781118960608.fbm00268)
9. [Fervidicoccus fontis gen. nov., sp. nov. (PDF, includes genome analysis abstract, Extremophiles 2013)](https://www.academia.edu/144679123/Fervidicoccus_fontis_gen_nov_sp_nov_an_anaerobic_thermophilic_crenarchaeote_from_terrestrial_hot_springs_and_proposal_of_Fervidicoccaceae_fam_nov_and_Fervidicoccales_ord_nov)
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*Topic: Encyclopedia › Life and health › Microorganisms and fungi › Archaea › Archaeal taxonomy and diversity › Crenarchaeota and TACK superphylum › Crenarchaeal orders (Thermoprotei) › Fervicoccales*
*Initially written Sep 17, 2026 · Reviewed: Sep 30, 2026 · Edited: Sep 30, 2026; Oct 11, 2026; Oct 15, 2026 · Last review: Sep 30, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license