Oxymonad

The Oxymonads (or Oxymonadida) are a group of flagellated protists found exclusively in the intestines of animals, mostly termites and other wood-eating insects. Along with the similar parabasalid flagellates, they harbor the symbiotic bacteria that are responsible for breaking down cellulose. There is no evidence for presence of mitochondria (not even anaerobic mitochondrion-like organelles like hydrogenosomes or mitosomes) in oxymonads^[1] and three species have been shown to completely lack any molecular markers of mitochondria.^[2]

Oxymonads
Monocercomonoides melolanthae
Scientific classification
Domain:	Eukaryota
(unranked):	Excavata
Phylum:	Metamonada
Class:	Preaxostyla
Order:	Oxymonadida Grassé 1952 emend. Cavalier-Smith 2003
Families
Oxymonadidae Polymastigidae Pyrsonymphidae Saccinobaculidae
Synonyms
Oxymonadales Polymastigales Engler 1898 Polymastigida Calkins 1902 Polymastigina Blochmann 1895 Polymastigoda Seligo 1886 Pyrsonymphales Pyrsonymphida Grassé 1952

It includes e.g. Dinenympha, Pyrsonympha, Oxymonas,^[3] Streblomastix,^[4] Monocercomonoides, and Blattamonas.^[5]

Characteristics

Most Oxymonads are around 50 μm in size and have a single nucleus, associated with four flagella. Their basal bodies give rise to several long sheets of microtubules, which form an organelle called an axostyle, but different in structure from the axostyles of parabasalids. The cell may use the axostyle to swim, as the sheets slide past one another and cause it to undulate. An associated fiber called the preaxostyle separates the flagella into two pairs. A few oxymonads have multiple nuclei, flagella, and axostyles.

Representation of an Oxymonad

1. Flagella (two pairs)
2. Basal bodies
3. Nucleus
4. Motile axostyle
5. Endoplasmic reticulum, the transport network for molecules going to specific parts of the cell
6. Reduced Golgi apparatus; modifies proteins and sends them out of the cell
7. Pinocytic pore, for filter feeding
8. Endosome, sorts material
9. Membrane-bound granules

Relationship to Trimastix and Paratrimastix

The free-living flagellates Trimastix and Paratrimastix are closely related to the oxymonads.^[6][7] They lack aerobic mitochondria and have four flagella separated by a preaxostyle, but unlike the oxymonads have a feeding groove. This character places the Oxymonads, Trimastix, and Paratrimastix among the Excavata, and in particular they may belong to the metamonads. Molecular phylogenetic studies indeed place Preaxostyla (oxymonads, Trimastix, and Paratrimastix) in Metamonada.^[8][9]

Taxonomy

Cladogram of Oxymonadida[10]

Polymastigidae Saccinobaculidae Oxymonadidae Opisthomitus Pyrsonymphidae

• Order Oxymonadida Grassé 1952 emend. Cavalier-Smith 2003^[11]
  • Family Oxymonadidae Kirby 1928 [Oxymonadaceae; Oxymonadinae Cleveland 1934]
    • Genus ?Metasaccinobaculus Freitas 1945
    • Genus Barroella Zeliff 1944 [Kirbyella Zeliff 1930 non Kirkaldy 1906 non Bolivar 1909]
    • Genus Microrhopalodina Grassé & Foa 1911 [Proboscidiella Kofoid & Swezy 1926]
    • Genus Opisthomitus Grassé 1952 non Duboscq & Grassé 1934
    • Genus Oxymonas Janicki 1915
    • Genus Sauromonas Grassé & Hollande 1952
  • Family Polymastigidae Bütschli 1884 [Polymastiginae Kirby 1931; Polymastigaceae; Streblomastigaceae; Streblomastigidae Kofoid & Swezy 1919]
    • Genus ?Paranotila Cleveland 1966
    • Genus ?Tubulimonoides Krishnamurthy & Sultana 1976
    • Genus Blattamonas Treitli et al. 2018
    • Genus Brachymonas (Grassé 1952) Treitli et al. 2018 non Hiraishi et al. 1995
    • Genus Monocercomonoides Travis 1932
    • Genus Polymastix Bütschli 1884 non Gruber 1884
    • Genus Streblomastix Kofoid & Swezy 1920
  • Family Pyrsonymphidae Grassé 1892 [Pyrsonymphaceae; Pyrsonymphinae Kirby 1937 nom. nud.; Dinenymphidae Grassé 1911; Dinenymphinae Cleveland et al. 1934; Dinenymphaceae]
    • Genus Dinenympha Leidy 1877 [Pyrsonympha (Dinenympha) (Leidy 1877) Koidzumi 1921]
    • Genus Pyrsonympha Leidy 1877 [Pyrsonema Kent 1881; Lophophora Comes 1910 non Coulter 1894 non Kraatz 1895 non Moeschler 1890]
  • Family Saccinobaculidae Brugerolle & Lee 2002 ex Cavalier-Smith 2012 [Saccinobaculinae Cleveland et al. 1934]
    • Genus Notila Cleveland 1950
    • Genus Saccinobaculus Cleveland-Hall & Sanders & Collier 1934

References

1. Hampl, Vladimir (2016), Archibald, John M.; Simpson, Alastair G.B.; Slamovits, Claudio H.; Margulis, Lynn (eds.), "Preaxostyla", Handbook of the Protists, Cham: Springer International Publishing, pp. 1–36, doi:10.1007/978-3-319-32669-6_8-1, ISBN 978-3-319-32669-6, retrieved 2024-04-15
2. Novák, Lukáš V. F.; Treitli, Sebastian C.; Pyrih, Jan; Hałakuc, Paweł; Pipaliya, Shweta V.; Vacek, Vojtěch; Brzoň, Ondřej; Soukal, Petr; Eme, Laura; Dacks, Joel B.; Karnkowska, Anna; Eliáš, Marek; Hampl, Vladimír (2023-12-07). Dutcher, Susan K. (ed.). "Genomics of Preaxostyla Flagellates Illuminates the Path Towards the Loss of Mitochondria". PLOS Genetics. 19 (12): e1011050. doi:10.1371/journal.pgen.1011050. ISSN 1553-7404. PMC 10703272. PMID 38060519.
3. Moriya S, Dacks JB, Takagi A, et al. (2003). "Molecular phylogeny of three oxymonad genera: Pyrsonympha, Dinenympha and Oxymonas". J. Eukaryot. Microbiol. 50 (3): 190–7. doi:10.1111/j.1550-7408.2003.tb00115.x. PMID 12836875. S2CID 26831383.
4. Treitli, Sebastian C.; Kolisko, Martin; Husník, Filip; Keeling, Patrick J.; Hampl, Vladimír (2019-09-24). "Revealing the metabolic capacity of Streblomastix strix and its bacterial symbionts using single-cell metagenomics". Proceedings of the National Academy of Sciences. 116 (39): 19675–19684. Bibcode:2019PNAS..11619675T. doi:10.1073/pnas.1910793116. ISSN 0027-8424. PMC 6765251. PMID 31492817.
5. Treitli, Sebastian C.; Kotyk, Michael; Yubuki, Naoji; Jirounková, Eliška; Vlasáková, Jitka; Smejkalová, Pavla; Šípek, Petr; Čepička, Ivan; Hampl, Vladimír (November 2018). "Molecular and Morphological Diversity of the Oxymonad Genera Monocercomonoides and Blattamonas gen. nov". Protist. 169 (5): 744–783. doi:10.1016/j.protis.2018.06.005. PMID 30138782.
6. Dacks JB, Silberman JD, Simpson AG, et al. (June 2001). "Oxymonads are closely related to the excavate taxon Trimastix". Mol. Biol. Evol. 18 (6): 1034–44. doi:10.1093/oxfordjournals.molbev.a003875. PMID 11371592.
7. Zhang, Qianqian; Táborský, Petr; Silberman, Jeffrey D.; Pánek, Tomáš; Čepička, Ivan; Simpson, Alastair G.B. (September 2015). "Marine Isolates of Trimastix marina Form a Plesiomorphic Deep-branching Lineage within Preaxostyla, Separate from Other Known Trimastigids (Paratrimastix n. gen.)". Protist. 166 (4): 468–491. doi:10.1016/j.protis.2015.07.003. PMID 26312987.
8. Zhang, Qianqian; Táborský, Petr; Silberman, Jeffrey D.; Pánek, Tomáš; Čepička, Ivan; Simpson, Alastair G.B. (September 2015). "Marine Isolates of Trimastix marina Form a Plesiomorphic Deep-branching Lineage within Preaxostyla, Separate from Other Known Trimastigids (Paratrimastix n. gen.)". Protist. 166 (4): 468–491. doi:10.1016/j.protis.2015.07.003. PMID 26312987.
9. Stairs, Courtney W.; Táborský, Petr; Salomaki, Eric D.; Kolisko, Martin; Pánek, Tomáš; Eme, Laura; Hradilová, Miluše; Vlček, Čestmír; Jerlström-Hultqvist, Jon; Roger, Andrew J.; Čepička, Ivan (December 2021). "Anaeramoebae are a divergent lineage of eukaryotes that shed light on the transition from anaerobic mitochondria to hydrogenosomes". Current Biology. 31 (24): 5605–5612.e5. Bibcode:2021CBio...31E5605S. doi:10.1016/j.cub.2021.10.010. PMID 34710348.
10. Treitlia, Sebastian C.; Kotykb, Michael; Yubukia, Naoji; Jirounkováa, Eliska; Vlasáková, Jitka; Smejkalováa, Pavla; Sípek, Petr; Cepicka, Ivan; Hampl, Vladimír (2018). "Molecular and Morphological Diversity of the Oxymonad Genera Monocercomonoides and Blattamonas gen. nov". Protist. 169 (5): 744–783. doi:10.1016/j.protis.2018.06.005. PMID 30138782.
11. "Part 1- Virae, Prokarya, Protists, Fungi". Collection of genus-group names in a systematic arrangement. Archived from the original on 14 August 2016. Retrieved 30 June 2016.