Editing Photosynthesis (section)

===Photosynthetic prokaryotic lineages===
Early photosynthetic systems, such as those in [[Green sulfur bacteria|green]] and [[purple sulfur]] and [[Chloroflexota|green]] and [[purple nonsulfur bacteria]], are thought to have been [[Anoxygenic photosynthesis|anoxygenic]], and used various other molecules than water as [[electron donor]]s. Green and purple sulfur bacteria are thought to have used [[hydrogen]] and [[sulfur]] as electron donors. Green nonsulfur bacteria used various [[amino acid|amino]] and other [[organic acid]]s as electron donors. Purple nonsulfur bacteria used a variety of nonspecific organic molecules. The use of these molecules is consistent with the geological evidence that Earth's early atmosphere was highly [[Reducing environment|reducing]] at [[History of Earth#Hadean and Archean Eons|that time]].<ref>{{cite book |vauthors= Gale J |date= 2009 |title= Astrobiology of Earth: The emergence, evolution and future of life on a planet in turmoil |publisher= Oxford University Press |isbn= 978-0-19-154835-2 |pages= 112–113 |url= https://books.google.com/books?id=64zn0nxDVUYC&pg=PA112 |access-date= 2019-04-17 |archive-url= https://web.archive.org/web/20230119181850/https://books.google.com/books?id=64zn0nxDVUYC&pg=PA112 |archive-date= 2023-01-19 |url-status= live }}</ref>

With a possible exception of [[Asgard (archaea)|Heimdallarchaeota]], photosynthesis is not found in [[archaea]].<ref>{{cite journal |vauthors= Liu R, Cai R, Zhang J, Sun C |title= Heimdallarchaeota harness light energy through photosynthesis. |journal= bioRxiv |date= February 2020 |doi= 10.1101/2020.02.20.957134 |s2cid= 213816522 }}</ref> [[Haloarchaea]] are [[photoheterotroph]]ic; they can absorb energy from the sun, but do not harvest carbon from the atmosphere and are therefore not photosynthetic.<ref>{{cite journal |vauthors= DasSarma S, Schwieterman EW |date= June 2021 |title= Early evolution of purple retinal pigments on Earth and implications for exoplanet biosignatures |journal= International Journal of Astrobiology |volume= 20 |issue= 3 |pages= 241–250 |arxiv= 1810.05150 |bibcode= 2021IJAsB..20..241D |doi= 10.1017/S1473550418000423 |doi-access= free |s2cid= 119341330 }} {{lay source |template=cite news |url= https://www.cbc.ca/radio/quirks/oct-27-2018-neanderthal-nursing-antarctica-s-singing-snows-fish-and-hook-injuries-a-1.4878288/purple-reign-life-on-earth-might-once-have-been-dominated-by-purple-microorganisms-1.4878298 |title= Purple reign: life on Earth might once have been dominated by purple microorganisms |date= 26 October 2018 |work= CBC/Radio-Canada }}</ref> Instead of chlorophyll they use rhodopsins, which convert light-energy to ion gradients but cannot mediate electron transfer reactions.<ref>{{cite journal |vauthors= Hamilton TL |date= August 2019 |title= The trouble with oxygen: The ecophysiology of extant phototrophs and implications for the evolution of oxygenic photosynthesis |journal= Free Radical Biology & Medicine |volume= 140 |pages= 233–249 |doi= 10.1016/j.freeradbiomed.2019.05.003 |doi-access= free |pmid= 31078729 |s2cid= 153285864 }}</ref><ref>{{cite journal |vauthors= Sharma AK, Walsh DA, Bapteste E, Rodriguez-Valera F, Ford Doolittle W, Papke RT |date= May 2007 |title= Evolution of rhodopsin ion pumps in haloarchaea |journal= BMC Evolutionary Biology |volume= 7 |issue= 1 |pages= 79 |bibcode= 2007BMCEE...7...79S |doi= 10.1186/1471-2148-7-79 |doi-access= free |pmc= 1885257 |pmid= 17511874 }}</ref>

In [[bacteria]] eight photosynthetic lineages are currently known:<ref>{{cite journal |vauthors= Xiong J |title= Photosynthesis: what color was its origin? |journal= Genome Biology |volume= 7 |issue= 12 |pages= 245 |date= 2006 |pmid= 17210067 |pmc= 1794423 |doi= 10.1186/gb-2006-7-12-245 |doi-access= free }}</ref><ref>{{cite journal |vauthors= Paoli L, Ruscheweyh HJ, Forneris CC, Hubrich F, Kautsar S, Bhushan A, Lotti A, Clayssen Q, Salazar G, Milanese A, Carlström CI, Papadopoulou C, Gehrig D, Karasikov M, Mustafa H, Larralde M, Carroll LM, Sánchez P, Zayed AA, Cronin DR, Acinas SG, Bork P, Bowler C, Delmont TO, Gasol JM, Gossert AD, Kahles A, Sullivan MB, Wincker P, Zeller G, Robinson SL, Piel J, Sunagawa S |display-authors= 6 |date= July 2022 |title= Biosynthetic potential of the global ocean microbiome |journal= Nature |volume= 607 |issue= 7917 |pages= 111–118 |doi= 10.1038/s43705-022-00201-9 |doi-access= free |pmc= 9758169 |pmid= 35732736 }}</ref><ref>{{cite journal |vauthors= He Z, Ferlez B, Kurashov V, Tank M, Golbeck JH, Bryant DA |title= Reaction centers of the thermophilic microaerophile, Chloracidobacterium thermophilum (Acidobacteria) I: biochemical and biophysical characterization |journal= Photosynthesis Research |volume= 142 |issue= 1 |pages= 87–103 |date= October 2019 |pmid= 31161318 |doi= 10.1007/s11120-019-00650-9 |bibcode= 2019PhoRe.142...87H |s2cid= 254941681 |url= https://scholarworks.montana.edu/xmlui/handle/1/15841 }}</ref><ref>{{cite journal |vauthors= Zeng Y, Feng F, Medová H, Dean J, Koblížek M |date= May 2014 |title= Functional type 2 photosynthetic reaction centers found in the rare bacterial phylum Gemmatimonadetes |journal= Proceedings of the National Academy of Sciences of the United States of America |volume= 111 |issue= 21 |pages= 7795–7800 |bibcode= 2014PNAS..111.7795Z |doi= 10.1073/pnas.1400295111 |doi-access= free |pmc= 4040607 |pmid= 24821787 }}</ref>

*[[Cyanobacteria]], the only prokaryotes performing oxygenic photosynthesis and the only prokaryotes that contain two types of photosystems (type I (RCI), also known as Fe-S type, and type II (RCII), also known as quinone type). The seven remaining prokaryotes have [[anoxygenic photosynthesis]] and use versions of either type I or type II.
*[[Green sulfur bacteria|Chlorobi]] (green sulfur bacteria) Type I
*[[Heliobacteria]] Type I
*[[Chloracidobacterium]] Type I
*[[Pseudomonadota|Proteobacteria]] (purple sulfur bacteria and purple non-sulfur bacteria) Type II (see: [[Purple bacteria]])
*[[Chloroflexota]] (green non-sulfur bacteria) Type II
*[[Gemmatimonadota]] Type II
*Eremiobacterota Type II