Prochloron

{{Short description|Genus of bacteria}}

{{Automatic taxobox

| image =

| taxon = Prochloron

| authority = R.A.Lewin, 1977

| subdivision_ranks = Species

| subdivision =

• P. didemni (Lewin, 1977) = Synechocystis didemni{{cite book|last1= Kühl|first1= Michael|first2= Anthony W.D.|last2= Larkum|chapter= The Microenvironment and Photosynthetic Performance of Prochloron sp. in Symbiosis with Didemnid Ascidians|title= Cellular origin and life in extreme habitats|publisher= Kluwer Academic Publisheres|volume= 3: Symbiosis, mechanisms and model systems|editor= Seckbach, J.|date= 2002|location= Dordrecht|pages= 273–290|url= http://bioold.science.ku.dk/mkuhl/pages/PDF/Kuhl&Larkum_2002.pdf}}

}}

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.{{cite journal|last1= La Roche|first1= J.|last2= van der Staay|first2= G.W.M.|last3= Ducret|first3= A.|last4= Aebersold|first4= R.|last5= Li|first5= R.|last6= Golden|first6= S.S.|last7= Hiller|first7= R.G.|last8= Wrench|first8= P.M.|last9= Larkum|first9= A.W.D.|last10= Green|first10= B.R.|year= 1996|title= Independent evolution of the prochlorophyte and green plant chlorophyll a/b light-harvesting proteins|journal= Proceedings of the National Academy of Sciences|volume= 93|issue= 26|pages= 15244–48|doi=10.1073/pnas.93.26.15244|pmc= 26388|pmid=8986795|bibcode= 1996PNAS...9315244L|doi-access= free}}

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. 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.{{cite journal |last1=Withers |first1=NW |last2=Alberte |first2=RS |last3=Lewin |first3=RA |last4=Thornder |first4=JP |last5=Britton |first5=G |last6=Goodwin |first6=TW |title=Photosynthetic unit size, carotenoids, and chlorophyll-protein composition of Prochloron sp., a prokaryotic green alga |journal= Proceedings of the National Academy of Sciences|date=May 1978 |volume=75 |issue=5 |pages=2301–2305 |doi=10.1073/pnas.75.5.2301 |pmid=16592528|pmc=392540 |bibcode=1978PNAS...75.2301W |doi-access=free }}{{cite journal |last1=Kuhl |first1=M |last2=Behrendt |first2=L |last3=Trampe |first3=E. |last4=Qvortrup |first4=K |last5=Schreiber |first5=U |last6=Borisov |first6=S. |last7=Larkum |first7=A |title=Microenvironmental Ecology of the chlorophyll b-containing Symbiotic Cyanabacterium Prochloron in the Didemnid Ascidian Lissoclinum patella |journal= Frontiers in Microbiology|date=November 2012 |volume=3 |page=402 |doi=10.3389/fmicb.2012.00402 |pmid=23226144 |pmc=3510431 |doi-access=free }}

Strictly speaking the name "Prochloron" {{au|Lewin 1977}} was not validly published under either ICNP or ICNafp. The two codes do each have a valid version of the genus:

• Prochloron {{au|Lewin 1977 ex Hoffmann and Greuter 1993}}, valid under ICNafp
• Prochloron {{au|(ex Lewin 1977) Florenzano et al. 1986}}, valid under ICNP by being published in Int. J. Syst. Bacteriol.

== Species ==

The only taxonomically valid species is P. didemni. Again there is a version in each of the two Codes.