# Photoautotroph

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Organisms that use light and inorganic carbon to produce organic materials

[Winogradsky column](/source/Winogradsky_column) showing Photoautotrophs in purple and green

**Photoautotrophs** are [organisms](/source/Organism) that can utilize [light energy](/source/Light_energy) from [sunlight](/source/Sunlight), and [elements](/source/Chemical_element) (such as [carbon](/source/Carbon)) from [inorganic compounds](/source/Inorganic_compound), to produce [organic materials](/source/Organic_material) needed to sustain their own [metabolism](/source/Metabolism) (i.e. [autotrophy](/source/Autotrophy)). Such biological activities are known as [photosynthesis](/source/Photosynthesis), and examples of such organisms include [plants](/source/Plant), [algae](/source/Algae) and [cyanobacteria](/source/Cyanobacteria).

[Eukaryotic](/source/Eukaryotic) photoautotrophs absorb photonic energy through the [photopigment](/source/Photopigment) [chlorophyll](/source/Chlorophyll) (a [porphyrin](/source/Porphyrin) [derivative](/source/Derivative)) in their [endosymbiont](/source/Endosymbiont) [chloroplasts](/source/Chloroplast), while [prokaryotic](/source/Prokaryotic) photoautotrophs use chlorophylls and [bacteriochlorophylls](/source/Bacteriochlorophyll) present in free-floating [cytoplasmic](/source/Cytoplasm) [thylakoids](/source/Thylakoid). Plants, algae, and cyanobacteria perform [oxygenic photosynthesis](/source/Oxygenic_photosynthesis) that produces [oxygen](/source/Oxygen) as a [byproduct](/source/Byproduct), while some bacteria perform [anoxygenic photosynthesis](/source/Anoxygenic_photosynthesis).

## Origin and the Great Oxidation Event

Chemical and geological evidence indicate that photosynthetic [cyanobacteria](/source/Cyanobacteria) existed about 2.6 billion years ago and [anoxygenic photosynthesis](/source/Anoxygenic_photosynthesis) had been taking place since a billion years before that.[1] Oxygenic [photosynthesis](/source/Photosynthesis) was the primary source of free oxygen and led to the [Great Oxidation Event](/source/Great_Oxidation_Event) roughly 2.4 to 2.1 billion years ago during the [Neoarchean](/source/Neoarchean)-[Paleoproterozoic](/source/Paleoproterozoic) boundary.[2] Although the end of the Great Oxidation Event was marked by a significant decrease in gross [primary productivity](/source/Primary_production) that eclipsed extinction events,[3] the development of [aerobic respiration](/source/Cellular_respiration) enabled more energetic metabolism of organic molecules, leading to [symbiogenesis](/source/Symbiogenesis) and the [evolution](/source/Evolution) of [eukaryotes](/source/Eukaryote), and allowing the diversification of [complex life](/source/Complex_life) on Earth.

## Prokaryotic photoautotrophs

Prokaryotic photoautotrophs include [Cyanobacteria](/source/Cyanobacteria), [Pseudomonadota](/source/Pseudomonadota), [Chloroflexota](/source/Chloroflexota), [Acidobacteriota](/source/Acidobacteriota), [Chlorobiota](/source/Green_sulfur_bacteria), [Bacillota](/source/Bacillota), [Gemmatimonadota](/source/Gemmatimonadota), and Eremiobacterota.[4]

Cyanobacteria is the only prokaryotic group that performs oxygenic [photosynthesis](/source/Photosynthesis). Anoxygenic photosynthetic bacteria use [PSI](/source/Photosystem_I)- and [PSII](/source/Photosystem_II)-like [photosystems](/source/Photosystem), which are pigment protein complexes for capturing light. Both of these photosystems use [bacteriochlorophyll](/source/Bacteriochlorophyll). There are multiple hypotheses for how oxygenic photosynthesis evolved. The loss hypothesis states that PSI and PSII were present in anoxygenic ancestor cyanobacteria from which the different branches of anoxygenic bacteria evolved. The fusion hypothesis states that the photosystems merged later through [horizontal gene transfer](/source/Horizontal_gene_transfer).[5] The most recent hypothesis suggests that PSI and PSII diverged from an unknown common ancestor with a protein complex that was coded by one gene. These photosystems then specialized into the ones that are found today.[4]

## Eukaryotic photoautotrophs

Eukaryotic photoautotrophs include [red algae](/source/Red_algae), [haptophytes](/source/Haptophyte), [stramenopiles](/source/Stramenopile), [cryptophytes](/source/Cryptomonad), [chlorophytes](/source/Chlorophyta), and [land plants](/source/Embryophyte).[6] These organisms perform [photosynthesis](/source/Photosynthesis) through organelles called [chloroplasts](/source/Chloroplast) and are believed to have originated about 2 billion years ago.[1] Comparing the genes of chloroplast and cyanobacteria strongly suggests that chloroplasts evolved as a result of [endosymbiosis](/source/Endosymbiont) with [cyanobacteria](/source/Cyanobacteria) that gradually lost the genes required to be free-living. However, it is difficult to determine whether all chloroplasts originated from a single, primary endosymbiotic event, or multiple independent events.[1] Some [brachiopods](/source/Brachiopod) (*[Gigantoproductus](/source/Gigantoproductus)*) and [bivalves](/source/Bivalve) (*[Tridacna](/source/Tridacna)*) also evolved photoautotrophy.[7]

## References

1. ^ [***a***](#cite_ref-:0_1-0) [***b***](#cite_ref-:0_1-1) [***c***](#cite_ref-:0_1-2) Olson, John M.; [Blankenship, Robert E.](/source/Robert_E._Blankenship) (2004). ["Thinking About the Evolution of Photosynthesis"](http://link.springer.com/10.1023/B:PRES.0000030457.06495.83). *Photosynthesis Research*. **80** (1–3): 373–386. [Bibcode](/source/Bibcode_(identifier)):[2004PhoRe..80..373O](https://ui.adsabs.harvard.edu/abs/2004PhoRe..80..373O). [doi](/source/Doi_(identifier)):[10.1023/B:PRES.0000030457.06495.83](https://doi.org/10.1023%2FB%3APRES.0000030457.06495.83). [ISSN](/source/ISSN_(identifier)) [0166-8595](https://search.worldcat.org/issn/0166-8595). [PMID](/source/PMID_(identifier)) [16328834](https://pubmed.ncbi.nlm.nih.gov/16328834). [S2CID](/source/S2CID_(identifier)) [1720483](https://api.semanticscholar.org/CorpusID:1720483).

1. **[^](#cite_ref-2)** Hodgskiss, Malcolm S. W.; Crockford, Peter W.; Peng, Yongbo; Wing, Boswell A.; Horner, Tristan J. (27 August 2019). ["A productivity collapse to end Earth's Great Oxidation"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6717284). *Proceedings of the National Academy of Sciences*. **116** (35): 17207–17212. [Bibcode](/source/Bibcode_(identifier)):[2019PNAS..11617207H](https://ui.adsabs.harvard.edu/abs/2019PNAS..11617207H). [doi](/source/Doi_(identifier)):[10.1073/pnas.1900325116](https://doi.org/10.1073%2Fpnas.1900325116). [ISSN](/source/ISSN_(identifier)) [0027-8424](https://search.worldcat.org/issn/0027-8424). [PMC](/source/PMC_(identifier)) [6717284](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6717284). [PMID](/source/PMID_(identifier)) [31405980](https://pubmed.ncbi.nlm.nih.gov/31405980).

1. **[^](#cite_ref-3)** Lyons, Timothy W.; Reinhard, Christopher T.; Planavsky, Noah J. (February 2014). ["The rise of oxygen in Earth's early ocean and atmosphere"](http://www.nature.com/articles/nature13068). *Nature*. **506** (7488): 307–315. [Bibcode](/source/Bibcode_(identifier)):[2014Natur.506..307L](https://ui.adsabs.harvard.edu/abs/2014Natur.506..307L). [doi](/source/Doi_(identifier)):[10.1038/nature13068](https://doi.org/10.1038%2Fnature13068). [ISSN](/source/ISSN_(identifier)) [0028-0836](https://search.worldcat.org/issn/0028-0836). [PMID](/source/PMID_(identifier)) [24553238](https://pubmed.ncbi.nlm.nih.gov/24553238). [S2CID](/source/S2CID_(identifier)) [4443958](https://api.semanticscholar.org/CorpusID:4443958).

1. ^ [***a***](#cite_ref-:1_4-0) [***b***](#cite_ref-:1_4-1) Sánchez-Baracaldo, Patricia; Cardona, Tanai (February 2020). ["On the origin of oxygenic photosynthesis and Cyanobacteria"](https://doi.org/10.1111%2Fnph.16249). *New Phytologist*. **225** (4): 1440–1446. [doi](/source/Doi_(identifier)):[10.1111/nph.16249](https://doi.org/10.1111%2Fnph.16249). [hdl](/source/Hdl_(identifier)):[10044/1/74260](https://hdl.handle.net/10044%2F1%2F74260). [ISSN](/source/ISSN_(identifier)) [0028-646X](https://search.worldcat.org/issn/0028-646X). [PMID](/source/PMID_(identifier)) [31598981](https://pubmed.ncbi.nlm.nih.gov/31598981).

1. **[^](#cite_ref-:2_5-0)** Björn, Lars (June 2009). ["The evolution of photosynthesis and chloroplasts"](https://www.researchgate.net/publication/299247771). *[Current Science](/source/Current_Science)*. **96** (11): 1466–1474.

1. **[^](#cite_ref-6)** Yoon, Hwan Su; Hackett, Jeremiah D.; Ciniglia, Claudia; Pinto, Gabriele; Bhattacharya, Debashish (May 2004). ["A Molecular Timeline for the Origin of Photosynthetic Eukaryotes"](https://academic.oup.com/mbe/article-lookup/doi/10.1093/molbev/msh075). *Molecular Biology and Evolution*. **21** (5): 809–818. [doi](/source/Doi_(identifier)):[10.1093/molbev/msh075](https://doi.org/10.1093%2Fmolbev%2Fmsh075). [ISSN](/source/ISSN_(identifier)) [1537-1719](https://search.worldcat.org/issn/1537-1719). [PMID](/source/PMID_(identifier)) [14963099](https://pubmed.ncbi.nlm.nih.gov/14963099).

1. **[^](#cite_ref-7)** George R. McGhee, Jr. (2019). [*Convergent Evolution on Earth. Lessons for the Search for Extraterrestrial Life*](https://books.google.com/books?id=bL60DwAAQBAJ&dq=largest+Gigantoproductus+giganteus&pg=PA47). MIT Press. p. 47. [ISBN](/source/ISBN_(identifier)) [9780262354189](https://en.wikipedia.org/wiki/Special:BookSources/9780262354189). Retrieved 23 August 2022.

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Adapted from the Wikipedia article [Photoautotroph](https://en.wikipedia.org/wiki/Photoautotroph) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Photoautotroph?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.