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Picozoa

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Picozoa
Movement of aPicomonas judraskedacell
Animation of the 3D structure ofPicomonas judraskeda
Scientific classificationEdit this classification
(unranked): Archaeplastida
Phylum: Picozoa
Seenivasan, Sausen, Medlin, Melkonian, 2013[1]
Genera

Picozoa,Picobiliphyta,Picobiliphytes,orBiliphytesareprotistsof aphylumof marine unicellularheterotrophiceukaryoteswith a size of less than about 3 micrometers. They were formerly treated aseukaryoticalgaeand the smallest member ofphotosynthetic picoplanktonbefore it was discovered they do not perform photosynthesis.[2]The first species identified therein isPicomonas judraskeda.[1]They probably belong in theArchaeplastidaas sister of theRhodophyta.[3][4][5]

They were formerly placed within thecryptomonads-haptophytes assemblage.[6]

Discovery[edit]

At the end of the 1990s the European project "Picodiv" clarified whichorganismsoccur inpicoplankton.In addition, for a period of two years, samples were taken in the Atlantic, in the Mediterranean, before the coast of Scotland, Alaska and Norway.[7][citation needed]Picobiliphyta were found particularly within the nutrient-poor ranges from cold coastal seas, where they can constitute up to 50 percent of thebiomass.[citation needed]

Affinities to other organisms[edit]

Picomonas judraskeda

Picozoa were first detected using18S ribosomal RNAgenes in 2007.[8]The identity of new organisms was deduced from a comparison of familiar and unfamiliar gene sequences. “The gene sequences found in these algae could not be associated with any previously known group of organisms”, explain Klaus Valentin andLinda Medlin,co-authors of the study andmolecular biologistsat theAlfred Wegener Institute for Polar and Marine ResearchinBremerhaven.[9]The algae in this study were found in plankton samples originating from various regions of the North Atlantic and the Mediterranean. The scientists have discovered a group of organisms which, despite being completely new to science, have a wide distribution. “This is a good indication for how much there is still to discover in the oceans, especially using molecular tools”, says Valentin.[9]

Apart from the unfamiliar gene sequences, the researchers also detectedphycobiliproteins.[10]Inred algae,for example, these proteins occur as pigments. But in this newly discovered group of algae, the phycobiliproteins appear to be contained inside theplastids,[11]where thephotosynthesisoccurs. Hence, it provides a clear indication that the researchers are dealing with previously unidentified group of algae. Referring to their small size and the presence of phycobiliproteins, the researchers named the new group "Picobiliphyta".[8]

Two studies published in 2011 found the hypothesis that biliphytes, or picobiliphytes, were photosynthetic was likely to be false. A 2011 study by an international team from the Monterey Bay Aquarium Research Institute, Dalhousie University and the Natural History Museum London found that cells in the Pacific Ocean did not have fluorescence indicative of photosynthetic pigments, and concluded "...biliphytes are likely not obligate photoautotrophs but rather facultative mixotrophs or phagotrophs, whereby transient detection of orange fluorescence could represent ingested prey items (e.g., the cyanobacterium Synechococcus)".[12]A study later in 2011, conducted by researchers atRutgers UniversityandBigelow Laboratory for Ocean Sciences,used whole genome shotgun sequence data from three individual picobiliphyte cells to show absence of plastid-targeted or photosystem proteins within the fragments of nuclear genome sequence they reconstructed. This again suggested that picobiliphytes areheterotrophs.[13][14]

Most recently, Seenivasan working in conjunction withMichael Melkonian(University of Cologne) and Linda Medlin (Marine Biological Association of the UK) formally described the picobiliphytes as the heterotrophic nanoflagellate phylum, Picozoa, and published thin sections of the cells.[1]Several unique features in the cell, such as a feeding organelle, substantiate their unique phylogenetic position, an unusual movement, and heterotrophic mode of nutrition. No traces of viral or bacterial particles were found inside these heterotrophic cells, which prompted these authors to suggest that they feed on very small organic particles.[1]

See also[edit]

References[edit]

  1. ^abcdSeenivasan R, Sausen N, Medlin LK, Melkonian M (2013). Waller RF (ed.)."Picomonas judraskeda gen. et sp. nov.: the first identified member of the Picozoa phylum nov., a widespread group of picoeukaryotes, formerly known as 'picobiliphytes'".PLOS ONE.8(3): e59565.Bibcode:2013PLoSO...859565S.doi:10.1371/journal.pone.0059565.PMC3608682.PMID23555709.
  2. ^Moreira D, López-García P (May 2014)."The rise and fall of Picobiliphytes: how assumed autotrophs turned out to be heterotrophs".BioEssays.36(5): 468–474.doi:10.1002/bies.201300176.PMC4133654.PMID24615955.
  3. ^Burki F, Kaplan M, Tikhonenkov DV, Zlatogursky V, Minh BQ, Radaykina LV, et al. (January 2016)."Untangling the early diversification of eukaryotes: a phylogenomic study of the evolutionary origins of Centrohelida, Haptophyta and Cryptista".Proceedings. Biological Sciences.283(1823): 20152802.doi:10.1098/rspb.2015.2802.PMC4795036.PMID26817772.
  4. ^Lax G, Eglit Y, Eme L, Bertrand EM, Roger AJ, Simpson AG (December 2018). "Hemimastigophora is a novel supra-kingdom-level lineage of eukaryotes".Nature.564(7736): 410–414.Bibcode:2018Natur.564..410L.doi:10.1038/s41586-018-0708-8.PMID30429611.S2CID205570993.
  5. ^Cavalier-Smith T, Chao EE, Lewis R (December 2015)."Multiple origins of Heliozoa from flagellate ancestors: New cryptist subphylum Corbihelia, superclass Corbistoma, and monophyly of Haptista, Cryptista, Hacrobia and Chromista".Molecular Phylogenetics and Evolution.93:331–362.doi:10.1016/j.ympev.2015.07.004.PMID26234272.
  6. ^Keeling P, Leander BS (28 October 2009) [8 September 2000]."Eukaryotes".Tree of Life Web Project.Retrieved2009-06-17.
  7. ^Massana R, Guillou L, Díez B, Pedrós-Alió C (September 2002)."Unveiling the organisms behind novel eukaryotic ribosomal DNA sequences from the ocean".Applied and Environmental Microbiology.68(9): 4554–4558.Bibcode:2002ApEnM..68.4554M.doi:10.1128/AEM.68.9.4554-4558.2002.PMC124113.PMID12200313.
  8. ^abNot F, Valentin K, Romari K, Lovejoy C, Massana R, Töbe K, et al. (January 2007)."Picobiliphytes: A Marine Picoplanktonic Algal Group with Unknown Affinities to Other Eukaryotes"(PDF).Science.315(5809): 253–255.Bibcode:2007Sci...315..253N.doi:10.1126/science.1136264.PMID17218530.S2CID22285394.
  9. ^ab"New Group Of Algae Discovered: Picobiliphytes".ScienceDaily.January 15, 2007.Retrieved2021-11-01.
  10. ^Hearn K (11 January 2007)."Bizarre New Form of Life Found in Arctic Ocean, Scientists Announce".National Geographic News.Archived fromthe originalon 11 February 2008.Retrieved2009-06-17.
  11. ^Aronsson H, Sandelius AS (2008).The Chloroplast: Interactions with the Environment (Plant Cell Monographs).Berlin: Springer. p. 9.ISBN978-3-540-68692-7.
  12. ^Kim E, Harrison JW, Sudek S, Jones MD, Wilcox HM, Richards TA, et al. (January 2011)."Newly identified and diverse plastid-bearing branch on the eukaryotic tree of life".Proceedings of the National Academy of Sciences of the United States of America.108(4): 1496–1500.Bibcode:2011PNAS..108.1496K.doi:10.1073/pnas.1013337108.PMC3029697.PMID21205890.
  13. ^Yoon HS, Price DC, Stepanauskas R, Rajah VD, Sieracki ME, Wilson WH, et al. (May 2011). "Single-cell genomics reveals organismal interactions in uncultivated marine protists".Science.332(6030): 714–717.Bibcode:2011Sci...332..714Y.doi:10.1126/science.1203163.PMID21551060.S2CID34343205.
  14. ^Worden AZ, Dupont C, Allen AE (June 2011)."Genomes of uncultured eukaryotes: sorting FACS from fiction".Genome Biology.12(6): 117.doi:10.1186/gb-2011-12-6-117.PMC3218834.PMID21722350.

External links[edit]

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