Prochloron (from the Greek pro (before) and the Greek chloros (green) ) is a genus of unicellular oxygenic photosynthetic prokaryotes commonly found as an extracellular symbiont on coral reefs, particularly in didemnid ascidians (sea squirts). Part of the phylum cyanobacteria, it was theorized (endosymbiotic theory) that Prochloron is a predecessor of the photosynthetic components, chloroplasts, found in photosynthetic eukaryotic cells. However this theory is largely refuted by phylogenetic studies which indicate Prochloron is not on the same line of descent that lead to chloroplast-containing algae and land plants.[2]
| Prochloron | |
|---|---|
Scientific classification 
| |
| Domain: | Bacteria |
| Phylum: | Cyanobacteria |
| Class: | Cyanophyceae |
| Order: | Synechococcales |
| Family: | Prochloraceae |
| Genus: | Prochloron R.A.Lewin, 1977 |
| Species | |
Prochloron was discovered in 1975 by Ralph A. Lewin of the Scripps Institution of Oceanography. Prochloron is one of three known prochlorophytes, cyanobacteria that contain both chlorophyll a and b bound to a special light-harvesting protein.[2] Surprisingly, unlike most cyanobacteria Prochloron do not contain the red or blue pigments called phycobilins, seen in many species of cyanobacteria. Repeated unsuccessful attempts to culture Prochloron outside a host make them the only known obligate photosymbionts in the phylum Chordata.[3][4]
Species
editThe only taxonomically valid species is P. didemni.
References
edit- ^ Kühl, Michael; Larkum, Anthony W.D. (2002). "The Microenvironment and Photosynthetic Performance of Prochloron sp. in Symbiosis with Didemnid Ascidians". In Seckbach, J. (ed.). Cellular origin and life in extreme habitats (PDF). Vol. 3: Symbiosis, mechanisms and model systems. Dordrecht: Kluwer Academic Publisheres. pp. 273–290.
- ^ a b La Roche, J.; van der Staay, G.W.M.; Ducret, A.; Aebersold, R.; Li, R.; Golden, S.S.; Hiller, R.G.; Wrench, P.M.; Larkum, A.W.D.; Green, B.R. (1996). "Independent evolution of the prochlorophyte and green plant chlorophyll a/b light-harvesting proteins". Proceedings of the National Academy of Sciences. 93 (26): 15244–48. Bibcode:1996PNAS...9315244L. doi:10.1073/pnas.93.26.15244. PMC 26388. PMID 8986795.
- ^ Withers, NW; Alberte, RS; Lewin, RA; Thornder, JP; Britton, G; Goodwin, TW (May 1978). "Photosynthetic unit size, carotenoids, and chlorophyll-protein composition of Prochloron sp., a prokaryotic green alga". Proceedings of the National Academy of Sciences. 75 (5): 2301–2305. Bibcode:1978PNAS...75.2301W. doi:10.1073/pnas.75.5.2301. PMC 392540. PMID 16592528.
- ^ Kuhl, M; Behrendt, L; Trampe, E.; Qvortrup, K; Schreiber, U; Borisov, S.; Larkum, A (November 2012). "Microenvironmental Ecology of the chlorophyll b-containing Symbiotic Cyanabacterium Prochloron in the Didemnid Ascidian Lissoclinum patella". Frontiers in Microbiology. 3: 402. doi:10.3389/fmicb.2012.00402. PMC 3510431. PMID 23226144.
- Guiry, M.D.; Guiry, G.M. (2008). "Prochloron". AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. Retrieved 2009-02-21.
- Waterbury, John, et al. Little Things Matter A Lot. Oceanus Magazine. 2004, 43(2).
- Yellowlees, David; et al. (2008). "Metabolic interactions between algal symbionts and invertebrate hosts". Plant, Cell and Environment. 31 (5): 679–694. doi:10.1111/j.1365-3040.2008.01802.x. PMID 18315536.