Breviatea

Breviatea
	Breviata anathema
Scientific classification
Domain:	Eukaryota
Clade:	Amorphea
Clade:	Obazoa
Class:	Breviatea; Cavalier-Smith, 2004
Order:	Breviatida; Cavalier-Smith, 2004
Family:	Breviatidae; Cavalier-Smith, 2013
Genera
	Breviata; Subulatomonas; Lenisia; Pygsuia;
Diversity
	4 species

Breviatea, commonly known as breviate amoebae,^[3] are a group of free-living, amitochondriate protists with uncertain phylogenetic position.^[4] They are biflagellate, and can live in anaerobic (oxygen-free) environments.^[4]^[3]^[5] They are currently placed in the Obazoa clade.^[6] They likely do not possess vinculin proteins.^[6] Their metabolism relies on fermentative production of ATP as an adaptation to their low-oxygen environment.^[4]

The lineage emerged roughly one billion years ago, at a time when the oxygen content of the Earth's oceans was low, and they thus developed anaerobic lifestyles. Together with Apusomonads, they are the closest relatives of the Opisthokonts, a group that includes animals and fungi.^[3]^[7]

Characteristics

Mitochondrion-related organelles

Mitochondrion-related organelles (MROs) are organelles that evolved from a degradation of ancestral, fully functional mitochondria. Among Breviatea, MROs are present in Pygsuia, Breviata and Subulatomonas. In the cells of Pygsuia, for which the complete transcriptome is known, there is a single smooth MRO that lacks a mitochondrial genome and most components of the electron transport chain. Of the citric acid cycle enzymes, which are present in the mitochondria in other organisms, only two are present in Pygsuia: fumarase and succinate dehydrogenase. In contrast, Lenisia cells contain multiple MROs with cristae.^[7]

Evolution

Breviatea is a clade of basal eukaryotes. They are closely related to the apusomonads and the Opisthokonta supergroup, and together they compose the larger clade Obazoa, which is the sister group to Amoebozoa.^[3] Within Breviatea, the four known species are distributed into smaller clades of two species each: one uniting Breviata with Subulatomonas, and one uniting Lenisia with Pygsuia.^[4]

Breviatea

	Breviata anathema

	Subulatomonas tetraspora

	Lenisia limosa

	Pygsuia biforma

Apusomonadida

Opisthokonta

	Holozoa

	Holomycota

Taxonomy

History

The class Breviatea was created in 2004 by British protozoologist Thomas Cavalier-Smith to group a problematic taxon previously known as ‘Mastigamoeba invertens’. This organism, initially classified in the Archamoebae within phylum Amoebozoa, appeared to strongly diverge in phylogenetic trees based on ribosomal RNA and had a structure very different from other Archamoebae. Because of these results, ‘M. invertens’ was separated into the order Breviatida, contained in the monotypic class Breviatea.^[2] The organism was eventually renamed Breviata anathema.^[8] A family-level rank for these amoebae, Breviatidae, was formally described by the same author in 2013.^[1]

Classification

There are currently four accepted genera, each containing only one species.

Breviata Walker, Dacks & Embley, 2006^[8]
- Breviata anathema Walker, Dacks & Embley, 2006
Lenisia Hamann et al., 2016^[4]
- Lenisia limosa Hamann et al., 2016
Pygsuia Brown et al., 2013^[3]
- Pygsuia biforma Brown et al., 2013
Subulatomonas Katz et al., 2011^[9]
- Subulatomonas tetraspora Katz et al., 2011

References

^ ^a ^b Cavalier-Smith, Thomas (May 2013). "Early evolution of eukaryote feeding modes, cell structural diversity, and classification of the protozoan phyla Loukozoa, Sulcozoa, and Choanozoa". European Journal of Protistology. 49 (2): 115–178 Document online. doi:10.1016/j.ejop.2012.06.001. ISSN 0932-4739. PMID 23085100.
^ ^a ^b ^c Cavalier-Smith, Thomas; Chao, Ema E.-Y.; Oates, Brian (2004). "Molecular phylogeny of Amoebozoa and the evolutionary significance of the unikont Phalansterium". European Journal of Protistology. 40: 21–48. doi:10.1016/j.ejop.2003.10.001.
^ ^a ^b ^c ^d ^e Brown, Matthew W.; Sharpe, Susan C.; Silberman, Jeffrey D.; Heiss, Aaron A.; Lang, B. Franz; Simpson, Alastair G. B.; Roger, Andrew J. (2013-10-22). "Phylogenomics demonstrates that breviate flagellates are related to opisthokonts and apusomonads". Proceedings of the Royal Society B: Biological Sciences. 280 (1769): 20131755. doi:10.1098/rspb.2013.1755. ISSN 0962-8452. PMC 3768317. PMID 23986111.
^ ^a ^b ^c ^d ^e Hamann, Emmo; Gruber-Vodicka, Harald; Kleiner, Manuel; et al. (2016-06-09). "Environmental Breviatea harbor mutualistic Arcobacter epibionts". Nature. 534 (7606): 254–258. Bibcode:2016Natur.534..254H. doi:10.1038/nature18297. ISSN 0028-0836. PMC 4900452. PMID 27279223.
^ Elsas, Jan Dirk van; Trevors, Jack T.; Rosado, Alexandre Soares; Nannipieri, Paolo (2019-04-05). Modern Soil Microbiology, Third Edition. CRC Press. ISBN 978-0-429-60240-5.
^ ^a ^b Kang, Seungho; Tice, Alexander K.; Stairs, Courtney W.; Jones, Robert E.; Lahr, Daniel J. G.; Brown, Matthew W. (2021-07-26). "The integrin-mediated adhesive complex in the ancestor of animals, fungi, and amoebae". Current Biology. 31 (14): 3073–3085.e3. doi:10.1016/j.cub.2021.04.076. ISSN 0960-9822. PMID 34077702. S2CID 235273235.
^ ^a ^b Leger, Michelle M.; Kolísko, Martin; Stairs, Courtney W.; Simpson, Alastair G. B. (2019). "Mitochondrion-Related Organelles in Free-Living Protists". In Tachezy, Jan (ed.). Hydrogenosomes and Mitosomes: Mitochondria of Anaerobic Eukaryotes. Microbiology Monographs. Vol. 9 (2nd ed.). Springer Cham. doi:10.1007/978-3-030-17941-0. ISBN 978-3-030-17941-0. S2CID 199511756.
^ ^a ^b Walker, Giselle; Dacks, Joel B.; Embley, T. Martin (2006). "Ultrastructural Description of Breviata anathema, N. Gen., N. Sp., the Organism Previously Studied as "Mastigamoeba invertens"". Journal of Eukaryotic Microbiology. 53 (2): 65–78. doi:10.1111/j.1550-7408.2005.00087.x. PMID 16579808. S2CID 31046569.
^ Katz, Laura A.; Grant, Jessica; Parfrey, Laura Wegener; Gant, Anastasia; O’Kelly, Charles J.; Anderson, O. Roger; Molestina, Robert E.; Nerad, Thomas (November 2011). "Subulatomonas tetraspora nov. gen. nov. sp. is a Member of a Previously Unrecognized Major Clade of Eukaryotes". Protist. 162 (5): 762–773. doi:10.1016/j.protis.2011.05.002. PMID 21723191.