Schizochytrium

Schizochytrium is a genus of unicellular eukaryotes in the family Thraustochytriaceae, which are found in coastal marine habitats. They are assigned to the Stramenopiles (heterokonts), a group which also contains kelp and various microalgae.

Schizochytrium
Scientific classification
(unranked):
SAR
Superphylum:
Heterokonta
Class:
Labyrinthulomycetes
Order:
Labyrinthulales
Family:
Thraustochytriaceae
Genus:
Schizochytrium

S. Goldst. & Belsky emend. T. Booth & C. E. Mill. [1]
Species

S. aggregatum[2]
S. limacinum[3]
S. minutum[2]

Lifecycle

Several stages occur in its lifecycle. The feeding form has a stiff, rounded body with cellular extensions used in feeding. Cells can transform into mobile flagellated cells with stiff tripartite hairs typical of the Stramenopiles. Cells can also grow and divide to form a cluster of cells which may become a sorus that produces biflagellated zoospores.

Relation to humans

Certain species produce large amounts of docosahexaenoic acid (DHA)[4] and are grown commercially for production of this oil for animal feeds, biomass, biofuels and direct human consumption in supplements and additives.[5]

In 2016, juvenile Nile tilapia were given a feed containing dried Schizochytrium in place of fish oil. When compared to a control group raised on regular feed, they exhibited higher weight gain and better feed conversion, and their flesh was higher in omega-3 fatty acids.[6][7] A 2020 study showed similar results and combined the feed with Nannochloropsis oculata for an entirely fish-free feed.[8][9]

DHA synthesis in Schizochytrium

DHA synthesis in Schizochytrium does not involve membrane-bound desaturases or fatty acid elongation enzymes such as those described for other eukaryotes.[10][11] Instead it is thought that DHA synthesis in Schizochytrium occurs via a Polyketide synthase (PKS)-based pathway, although the primary structures of the Polyketide synthases do not conform to any known class of PKS proteins.[10][12] Homology between Shewanella and Schizochytrium PKS genes suggests that the genes involved in this pathway underwent lateral gene transfer.[10]

References
  1. Rinka Yokoyama & Daiske Honda (2007). "Taxonomic rearrangement of the genus Schizochytrium sensu lato based on morphology, chemotaxonomic characteristics, and 18S rRNA gene phylogeny (Thraustochytriaceae, Labyrinthulomycetes): emendation for Schizochytrium and erection of Aurantiochytrium and Oblongichytrium gen. nov". Mycoscience. 48 (4): 199–211. doi:10.1007/s10267-006-0362-0.
  2. "Schizochytrium". www.uniprot.org.
  3. Honda, Daiske; Yokochi, Toshihiro; Nakahara, Toro; Erata, Mayumi; Higashihara, Takanori (April 1998). "Schizochytrium limacinum sp. nov., a new thraustochytrid from a mangrove area in the west Pacific Ocean". Mycological Research. 102 (4): 439–448. doi:10.1017/S0953756297005170.
  4. Yue Jiang; King-Wai Fan; Raymond Tsz-Yeung Wong & Feng Chen (2004). "Fatty acid composition and squalene content of the marine microalga Schizochytrium mangrovei". Journal of Agricultural and Food Chemistry. 52 (5): 1196–1200. doi:10.1021/jf035004c. PMID 14995120.
  5. Whoriskey, Peter (5 June 2017). "How millions of cartons of 'organic' milk contain an oil brewed in industrial vats of algae". The Washington Post. Retrieved 9 June 2017.
  6. Coxworth, Ben (June 6, 2016). "Scientists take the fish out of fish food". www.gizmag.com. Retrieved 2016-06-08.
  7. Sarker, Pallab K.; Kapuscinski, Anne R.; Lanois, Alison J.; Livesey, Erin D.; Bernhard, Katie P.; Coley, Mariah L. (2016-06-03). "Towards Sustainable Aquafeeds: Complete Substitution of Fish Oil with Marine Microalga Schizochytrium sp. Improves Growth and Fatty Acid Deposition in Juvenile Nile Tilapia ( Oreochromis niloticus )". PLOS ONE. 11 (6): e0156684. Bibcode:2016PLoSO..1156684S. doi:10.1371/journal.pone.0156684. ISSN 1932-6203. PMC 4892564. PMID 27258552.
  8. "Research breakthrough achieves fish-free aquaculture feed that raises key standards". phys.org. Retrieved 9 December 2020.
  9. Sarker, Pallab K.; Kapuscinski, Anne R.; McKuin, Brandi; Fitzgerald, Devin S.; Nash, Hannah M.; Greenwood, Connor (12 November 2020). "Microalgae-blend tilapia feed eliminates fishmeal and fish oil, improves growth, and is cost viable". Scientific Reports. 10 (1): 19328. doi:10.1038/s41598-020-75289-x. ISSN 2045-2322. PMC 7665073. PMID 33184333. Retrieved 9 December 2020. Available under CC BY 4.0.
  10. Metz, James G.; Roessler, Paul; Facciotti, Daniel; Levering, Charlene; Dittrich, Franziska; Lassner, Michael; Valentine, Ray; Lardizabal, Kathryn; Domergue, Frederic (2001-07-13). "Production of Polyunsaturated Fatty Acids by Polyketide Synthases in Both Prokaryotes and Eukaryotes". Science. 293 (5528): 290–293. doi:10.1126/science.1059593. ISSN 0036-8075. PMID 11452122.
  11. Matsuda, Takanori; Sakaguchi, Keishi; Hamaguchi, Rie; Kobayashi, Takumi; Abe, Eriko; Hama, Yoichiro; Hayashi, Masahiro; Honda, Daiske; Okita, Yuji (2012-06-01). "Analysis of Δ12-fatty acid desaturase function revealed that two distinct pathways are active for the synthesis of PUFAs in T. aureum ATCC 34304". Journal of Lipid Research. 53 (6): 1210–1222. doi:10.1194/jlr.M024935. ISSN 0022-2275. PMC 3351828. PMID 22368282.
  12. Huang, Jianzhong; Jiang, Xianzhang; Zhang, Xiaowei; Chen, Weihua; Tian, Baoyu; Shu, Zhengyu; Hu, Songnian (2008). "Expressed sequence tag analysis of marine fungus Schizochytrium producing docosahexaenoic acid". Journal of Biotechnology. 138 (1–2): 9–16. doi:10.1016/j.jbiotec.2008.07.1994. PMID 18755227.


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