Pirsonia
| Pirsonia | |
|---|---|
 | |
| Scanning electron micrograph of Pirsonia diadema auxosomes infecting the diatom Coscinodiscus radiatus. Scale bar: 5 μm | |
Scientific classification  | |
| Domain: | Eukaryota |
| Clade: | Sar |
| Clade: | Stramenopiles |
| Phylum: | Bigyromonadea |
| Class: | Pirsonea |
| Order: | Pirsoniales |
| Family: | Pirsoniaceae |
| Genus: | Pirsonia Schnepf, Debres & Elbrachter 1990[1] |
| Type species | |
| Pirsonia guinardie Schnepf, Drebes & Elbrächter 1990[1] | |
| Species | |
 | |
| Geographical distribution of environmental DNA sequences assigned to Pirsonia, as recorded through the Tara Oceans expedition | |
Pirsonia is a genus of marine single-celled parasitoids of diatoms. It has a distinct life cycle: flagellate cells differentiate into 'auxosomes' when contacting the surface of a host diatom, and feed through another cell type, the 'trophosome', which develops inside the host and digests its cytoplasm.
The genus Pirsonia was described in 1990. It is the only parasitic genus in the order Pirsoniales, a group of otherwise free-living marine stramenopiles. To date, six species have been described and reported from across the globe. One species formerly assigned to Pirsonia due to its similar lifestyle, P. mucosa, is an evolutionarily distant cercozoan that was eventually assigned to its own genus, Pseudopirsonia.
Description
[edit]Species of Pirsonia are parasitoid nanoflagellates with small and flexible cells and a unique feeding mode and life cycle. The flagellate stages (zoospores) of Pirsonia have a flagellar organization similar to other Stramenopiles, a diverse lineage of protists characterized by tripartite hair-like extensions called mastigonemes present in one of the two flagella. Zoospore sizes range from 6 to 13 μm in length and 3 to 6 μm in width; the shorter anterior flagellum measures 15 to 25 μm, while the longer posterior flagellum measures 15 to 40 μm. Cyst formation has only been observed in a few species.[2]
The life cycle of Pirsonia begins with motile zoospores with two flagella attaching to the frustule of a diatom host. The zoospores lose their flagella and differentiate into 'auxosomes', the main parasitic cell bodies that remain on the surface of the frustule. These auxosomes squeeze a pseudopod into the cell, either through the natural tubular openings of the frustule (rimoportulae or labiate processes) or between the girdle bands. This pseudopod then transforms into a 'trophosome', a different cell type that phagocytes and digests the contents of the diatom cytoplasm (i.e., the protoplast). The digestive material is carried to the auxosome, which consequently grows and divides. After the death of the host cell, the auxosomes detach from the trophosomes and transform into motile 'flagellate mother cells', which eventually divide and differentiate into zoospores, completing the life cycle.[2][3]
Ecology
[edit]Pirsonia is a genus of marine parasitoids with a global distribution.[3] They specialize in infecting planktonic diatoms. As parasitoids, they infect, consume and kill their diatom hosts.[2] Their life cycle is rapid and highly virulent, capable of causing total diatom population collapse in culture.[3]
Evolution
[edit]The genus Pirsonia is located within Bigyromonada, a group of Stramenopiles closely related to the Pseudofungi, which contains a major parasitic group, the oomycetes. Bigyromonads are mostly free-living heterotrophic flagellates. For instance, the genus Koktebelia, one of the closest relatives of Pirsonia, is a free-living predator of other eukaryotes. The sister clade of Pirsonia, Noirmoutieria, is another free-living phagotroph that consumes heterotrophic flagellates and diatoms. As such, Pirsonia represents an independent and recent evolution towards parasitism within the Stramenopiles. The cladogram below summarizes the position of Pirsonia among Stramenopiles, highlighting the transitions to parasitism with *.[3][4]
Taxonomy
[edit]The genus Pirsonia and its type species Pirsonia guinardie were described in 1990 by E. Schnepf, G. Drebes and M. Elbrächter. The species was discovered parasitizing the centric marine diatom Guinardia flaccida in the North Sea. Due to its unique life cycle, with differentiation into trophosome and auxosome, it was left with no certain taxonomic position (as Mastigophora incertae sedis).[1] Electron microscopy observations revealed that the flagellate stages of Pirsonia present stramenopile flagella, with tripartite hair-like extensions (mastigonemes). However, there were some differences with the typical stramenopile organization of the flagellar cytoskeleton, leading the authors to wait for genetic analyses to establish its position within the stramenopiles. Six species were added to the genus: P. diadema, P. eucampiae, P. formosa, P. mucosa, P. punctigerae and P. verrucosa.[5][6]
The first molecular phylogenetic analysis that included species of Pirsonia was published in 2004. It confirmed the position of all species firmly within the stramenopiles, near the hyphochytrids, with the exception of P. mucosa which was revealed to be a cercozoan and placed under a separate genus Pseudopirsonia.[2] A second analysis in 2006 confirmed these findings, and the genus was placed into its own family Pirsoniaceae and order Pirsoniales (under the botanical code, Pirsoniida under the zoological code).[7][8] Pirsonia was the sole genus of Pirsoniales until 2022, when additional genera Feodosia and Koktebelia were described, followed by Bordeauxia, Bullionia and Noirmoutieria in 2024. In these studies, another species P. chemainus was described, bringing the total to six.[9][4]
Species
[edit]| Name | Diatom hosts | Type locality | Ref |
|---|---|---|---|
| Pirsonia chemainus Tikhonenkov, Cho & Keeling in Cho et al. 2022 | Unknown hosts | Strait of Georgia, Canada | [9] |
| Pirsonia diadema Kühn in Kühn et al. 1996 | Coscinodiscus granii, C. radiatus, C. wailesii | Wadden Sea (near Helgoland) | [6][3] |
| Pirsonia eucampiae Kühn in Kühn et al. 1996 | Eucampia zodiacus | Wadden Sea (near List) | [6] |
| Pirsonia formosa Kühn in Kühn et al. 1996 | Rhizosolenia setigera, Leptocylindrus danicus, Cerataulina pelagica | Wadden Sea (near Helgoland) | [6] |
| Pirsonia guinardie Schnepf, Debres & Elbrachter 1990 | Guinardia flaccida | Wadden Sea (near List) | [1] |
| Pirsonia punctigerae Schweikert & Schnepf 1977 | Thalassiosira punctigerae | Wadden Sea (near List) | [5] |
| Pirsonia verrucosa Kühn in Kühn et al. 1996 | Guinardia delicatula | Wadden Sea (near Helgoland) | [6][10] |
References
[edit]- 1 2 3 4 Schnepf, E.; Drebes, G.; Elbrächter, M. (1990). "Pirsonia guinardiae, gen. et spec. nov.: A parasitic flagellate on the marine diatom Guinardia flaccida with an unusual mode of food uptake". Helgoländer Meeresuntersuchungen. 44 (2): 275–293. doi:10.1007/BF02365468. ISSN 0174-3597.
- 1 2 3 4 Kühn, Stefanie; Medlin, Linda; Eller, Gundula (2004). "Phylogenetic Position of the Parasitoid Nanoflagellate Pirsonia inferred from Nuclear-Encoded Small Subunit Ribosomal DNA and a Description of Pseudopirsonia n. gen. and Pseudopirsonia mucosa (Drebes) comb. nov". Protist. 155 (2): 143–156. doi:10.1078/143446104774199556.
- 1 2 3 4 5 Mathur, Varsha; Irwin, Nicholas A. T.; Galindo, Luis Javier; Alacid, Elisabet; Moog, Kevin; et al. (21 July 2026). "Molecular and cellular insights into the parasitic infection of bloom-forming marine diatoms by Pirsonia diadema". Nature Microbiology. 11 (9): 2478–2492. doi:10.1038/s41564-026-02421-4. PMC 13524835. PMID 42481696.
- 1 2 Prokina, Kristina I.; Yubuki, Naoji; Tikhonenkov, Denis V.; Ciobanu, Maria Christina; López‐García, Purificación; Moreira, David (2024). "Refurbishing the marine parasitoid order Pirsoniales with newly (re)described marine and freshwater free‐living predators". Journal of Eukaryotic Microbiology. 71 (6) e13061. doi:10.1111/jeu.13061. ISSN 1066-5234. PMC 11603286. PMID 39350673.
- 1 2 Schweikert, Michael; Schnepf, Eberhard (1997). "Light and electron microscopical observations on Pirsonia punctigerae spec, nov., a nanoflagellate feeding on the marine centric diatom Thalassiosira punctigera". European Journal of Protistology. 33 (2): 168–177. doi:10.1016/S0932-4739(97)80033-8.
- 1 2 3 4 5 Kühn, S. F.; Drebes, G.; Schnepf, E. (1996). "Five new species of the nanoflagellate Pirsonia in the German Bight, North Sea, feeding on planktic diatoms". Helgoländer Meeresuntersuchungen. 50 (2): 205–222. doi:10.1007/BF02367152. ISSN 0174-3597.
- ↑ Cavalier-Smith, Thomas; Chao, Ema E-Y. (22 March 2006). "Phylogeny and Megasystematics of Phagotrophic Heterokonts (Kingdom Chromista)". Journal of Molecular Evolution. 62 (4): 388–420. doi:10.1007/s00239-004-0353-8. ISSN 0022-2844.
- ↑ Cavalier-Smith, Thomas (5 September 2017). "Kingdom Chromista and its eight phyla: a new synthesis emphasising periplastid protein targeting, cytoskeletal and periplastid evolution, and ancient divergences". Protoplasma. 255 (1): 297–357. doi:10.1007/s00709-017-1147-3. PMC 5756292. PMID 28875267.
- 1 2 Cho, Anna; Tikhonenkov, Denis V.; Hehenberger, Elisabeth; Karnkowska, Anna; Mylnikov, Alexander P.; Keeling, Patrick J. (2022). "Monophyly of diverse Bigyromonadea and their impact on phylogenomic relationships within stramenopiles" (PDF). Molecular Phylogenetics and Evolution. 171 (107468) 107468. doi:10.1016/j.ympev.2022.107468. ISSN 1055-7903. PMID 35358688. S2CID 247815732.
- ↑ Tillmann, Urban; Hesse, Karl-Jürgen; Tillmann, Anette (1999). "Large-scale parasitic infection of diatoms in the Northfrisian Wadden Sea". Journal of Sea Research. 42 (3): 255–261. doi:10.1016/S1385-1101(99)00029-5.