Green sulfur bacteria: Difference between revisions

Green sulfur bacteria
	Green sulfur bacteria in a Winogradsky column
Scientific classification
Domain:	Bacteria
(unranked):	Bacteroidota–Chlorobiota group
Phylum:	Chlorobiota; Iino et al. 2021
Class:	"Chlorobia"; Garrity and Holt 2001
Order:	Chlorobiales; Gibbons and Murray 1978 (Approved Lists 1980)
Families and Genera
	Chlorobiaceae Copeland 1956 (Approved Lists 1980) Ancalochloris Gorlenko and Lebedeva 1971 (Approved Lists 1980); Chlorobaculum Imhoff 2003; Chlorobium Nadson 1906 (Approved Lists 1980); Chloroherpeton Gibson et al. 1985; "Chloroplana" Dubinina and Gorlenko 1975; "Clathrochloris" Geitler 1925; Pelodictyon Lauterborn 1913 (Approved Lists 1980); Prosthecochloris Gorlenko 1970 (Approved Lists 1980); ; "Candidatus Thermochlorobacteriaceae" Liu et al. 2012 "Candidatus Thermochlorobacter" Liu et al. 2012; ;
Synonyms
	Chlorobiota: "Chlorobi" Iino et al. 2010; "Chlorobi" Garrity and Holt 2001; "Chlorobaeota" Oren et al. 2015; "Chlorobiota" Whitman et al. 2018; ; Chlorobiota: "Chlorobia" Whitman et al. 2018; Chlorobea Cavalier-Smith 2002; "Chlorobiia" Cavalier-Smith 2020; ; Chlorobiales: "Chlorobiales" Garrity and Holt 2001; ; Chlorobiaceae: "Chlorobiaceae" Garrity and Holt 2001; ;

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The green sulfur bacteria are a phylum of obligately anaerobic photoautotrophic bacteria that metabolize sulfur.^[4]

Green sulfur bacteria are nonmotile (except Chloroherpeton thalassium, which may glide) and capable of anoxygenic photosynthesis.^[4]^[5] They live in anaerobic aquatic environments.^[6] In contrast to plants, green sulfur bacteria mainly use sulfide ions as electron donors.^[7] They are autotrophs that utilize the reverse tricarboxylic acid cycle to perform carbon fixation.^[8] They are also mixotrophs and reduce nitrogen.^[9]^[10]

Characteristics

Green sulfur bacteria are gram-negative rod or spherical shaped bacteria. Some types of green sulfur bacteria have gas vacuoles that allow for movement. They are photolithoautotrophs, and use light energy and reduced sulfur compounds as the electron source.^[11] Electron donors include H₂, H₂S, S. The major photosynthetic pigment in these bacteria is Bacteriochlorophylls c or d in green species and e in brown species, and is located in the chlorosomes and plasma membranes.^[12] Chlorosomes are a unique feature that allow them to capture light in low-light conditions.^[13]

Habitat

The majority of green sulfur bacteria are mesophilic, preferring moderate temperatures, and all live in aquatic environments. They require anaerobic conditions and reduced sulfur; they are usually found in the top millimeters of sediment. They are capable of photosynthesis in low light conditions. ^[14]

The Black Sea, an extremely anoxic environment, was found to house a large population of green sulfur bacteria at about 100 m depth. Due to the lack of light available in this region of the sea, most bacteria were photosynthetically inactive. The photosynthetic activity detected in the sulfide chemocline suggests that the bacteria need very little energy for cellular maintenance.^[15]

A species of green sulfur bacteria has been found living near a black smoker off the coast of Mexico at a depth of 2,500 m in the Pacific Ocean. At this depth, the bacterium, designated GSB1, lives off the dim glow of the thermal vent since no sunlight can penetrate to that depth.^[16]

Green sulfur bacteria has also been found living on coral reef colonies in Taiwan, they make up the majority of a "green layer" on these colonies. They likely play a role in the coral system, and there could be a symbiotic relationship between the bacteria and the coral host.^[17] The coral could provide an anaerobic environment and a source of carbon for the bacteria. The bacteria can provide nutrients and detoxify the coral by oxidizing sulfide.^[18]

One type of green sulfur bacteria, Chlorobium tepidum, has been found in sulfur springs. These organisms are thermophilic, unlike most other green sulfur bacteria.^[19]

Phylogeny

The currently accepted phylogeny is based on 16S rRNA-based LTP release 123 by The All-Species Living Tree Project.^[20]

Ignavibacteriota (outgroup)

Chlorobiota

Chloroherpeton thalassium Gibson et al. 1985

Prosthecochloris

	P. aestuarii Gorlenko 1970 emend. Imhoff 2003 (type sp.)

	P. vibrioformis (Pelsh 1936) Imhoff 2003

Chlorobium chlorovibrioides (Gorlenko et al. 1974) Imhoff 2003

Chlorobaculum

	C. tepidum (Wahlund et al. 1996) Imhoff 2003 (type sp.)

	C. thiosulfatiphilum Imhoff 2003

Chlorobium

C. luteolum (Schmidle 1901) emend. Imhoff 2003

C. phaeovibrioides Pfennig 1968 emend. Imhoff 2003

C. limicola Nadson 1906 emend. Imhoff 2003 (type sp.)

	C. clathratiforme (Szafer 1911) emend. Imhoff 2003

	C. phaeobacteroides Pfennig 1968 emend. Imhoff 2003

Specific characteristics of genera

Green sulfur bacteria are family Chlorobiaceae. There are four genera; Chloroherpeton, Prosthecochloris, Chlorobium and Chlorobaculum. Characteristics used to distinguish between these genera include some metabolic properties, pigments, cell morphology and absorption spectra. However, it is difficult to distinguish these properties and therefore the taxonomic division is sometimes unclear.^[21]

Generally, Chlorobium are rod or vibroid shaped and some species contain gas vesicles. They can develop as single or aggregate cells. They can be green or dark brown. The green strains use photosynthetic pigments Bchl c or d with chlorobactene carotenoids and the brown strains use photosynthetic pigment Bchl e with isorenieratene carotenoids. Low amounts of salt are required for growth.^[21]

Prosthecochloris are made up of vibroid, ovid or rod shaped cells. They start as single cells that form appendages that do not branch, referred to as non-branching prosthecae. They can also form gas vesicles. The photosynthetic pigments present include Bchl c, d or e. Furthermore, salt is necessary for growth.^[21]

Chlorobaculum develop as single cells and are generally vibroid or rod-shaped. Some of these can form gas vesicles. The photosynthetic pigments in this genus are Bchl c, d or e. Some species require NaCl (sodium chloride) for growth. Members of this genus used to be a part of the genus Chlorobium, but have formed a separate lineage.^[21]

The genus Chloroherpeton is unique because members of this genus are motile. They are flexing long rods, and can move by gliding. They are green in color and contain the photosynthetic pigment Bchl c as well as γ-carotene. Salt is required for growth.^[21]

Metabolism

Photosynthesis

The green sulfur bacteria use a Type I reaction center for photosynthesis. Type I reaction centers are the bacterial homologue of photosystem I (PSI) in plants and cyanobacteria. The GSB reaction centers contain bacteriochlorophyll a and are known as P840 reaction centers due to the excitation wavelength of 840 nm that powers the flow of electrons. In green sulfur bacteria the reaction center is associated with a large antena complex called the chlorosome that captures and funnels light energy to the reaction center. The chlorosomes have a peak absorption in the far red region of the spectrum between 720-750 nm because they contain bacteriochlorophyll c, d and e.^[22] A protein complex called the Fenna-Matthews-Olson complex (FMO) is physically located between the chlorosomes and the P840 RC. The FMO complex helps efficiently transfer the energy absorbed by the antena to the reaction center.

PSI and Type I reaction centers are able to reduce ferredoxin (Fd), a strong reductant that can be used to fix CO
₂ and reduce NADPH. Once the reaction center (RC) has given an electron to Fd it becomes an oxidizing agent (P840⁺) with a reduction potential of around +300 mV. While this is not positive enough to strip electrons from water to synthesize O
₂ (E
₀ = +820 mV), it can accept electrons from other sources like H
₂S, thiosulphate or Fe²⁺
ions.^[23] This transport of electrons from donors like H
₂S to the acceptor Fd is called linear electron flow or linear electron transport. The oxidation of sulfide ions leads to the production of sulfur as a waste product that accumulates as globules on the extracellular side of the membrane. These globules of sulfur give green sulfur bacteria their name. When sulfide is depleted, the sulfur globules are consumed and further oxidized to sulfate. However, the pathway of sulfur oxidation is not well-understood.^[7]

Instead of passing the electrons onto Fd, the Fe-S clusters in the P840 reaction center can transfer the electrons to menaquinone (MQ:MQH
₂) which returns the electrons to the P840⁺ via an electron transport chain (ETC). On the way back to the RC the electrons from MQH2 pass through a cytochrome bc₁ complex (similar to the complex III of mitochondria) that pumps H⁺
ions across the membrane. The electrochemical potential of the protons across the membrane is used to synthesize ATP by the F_oF₁ ATP synthase. This cyclic electron transport is responsible for converting light energy into cellular energy in the form of ATP.^[22]

Sulfur metabolism

Green sulfur bacteria oxidize inorganic sulfur compounds to use as electron donors for anaerobic photosynthesis, specifically in carbon dioxide fixation. They usually prefer to utilize sulfide over other sulfur compounds as an electron donor, however they can utilize thiosulfate or H₂.^[24] The intermediate is usually sulfur, which is deposited outside of the cell,^[25] and the end product is sulfate. The sulfur, which is deposited extracellularly, is in the form of sulfur globules, which can be later oxidized completely.^[24]

The mechanisms of sulfur oxidation in green sulfur bacteria are not well characterized. Some enzymes thought to be involved in sulfide oxidation include flavocytochrome c, sulfide:quinone oxidoreductase and the Sox system. Flavocytochrome can catalyze the transfer of electrons to cytochromes from sulfide, and these cytochromes could then move the electrons to the photosynthetic reaction center. However, not all green sulfur bacteria produce this enzyme, demonstrating that it is not needed for the oxidation of sulfide. Sulfide:quinone oxidoreductase (SQR) also helps with electron transport, but, when alone, has been found to produce decreased rates of sulfide oxidation in green sulfur bacteria, suggesting that there is a different, more effective mechanism.^[24] However, most green sulfur bacteria contain a homolog of the SQR gene.^[26] The oxidation of thiosulfate to sulfate could be catalyzed by the enzymes in the Sox system.^[24]

It is thought that the enzymes and genes related to sulfur metabolism were obtained via horizontal gene transfer during the evolution of green sulfur bacteria.^[26]

Carbon fixation

Green sulfur bacteria are photoautotrophs: they not only get energy from light, they can grow using carbon dioxide as their sole source of carbon. They fix carbon dioxide using the reverse tricarboxylic acid cycle (rTCA) cycle^[8] where energy is consumed to reduce carbon dioxide, rather than oxidize as seen in the forward TCA cycle,^[8] in order to synthesize pyruvate and acetate. These molecules are used as the raw materials to synthesize all the building blocks a cell needs to generate macromolecules. The rTCA cycle is highly energy efficient enabling the bacteria to grow under low light conditions.^[27] However it has several oxygen sensitive enzymes that limits its efficiency in aerobic conditions.^[27]

The reactions of reversal of the oxidative tricarboxylic acid cycle are catalyzed by four enzymes:^[8]

pyruvate:ferredoxin (Fd) oxidoreductase:
acetyl-CoA + CO2 + 2Fdred + 2H+ ⇌ pyruvate + CoA + 2Fdox
ATP citrate lyase:
ACL, acetyl-CoA + oxaloacetate + ADP + Pi ⇌ citrate + CoA + ATP
α-keto-glutarate:ferredoxin oxidoreductase:
succinyl-CoA + CO2 + 2Fdred + 2H+ ⇌ α-ketoglutarate + CoA + 2Fdox
fumarare reductase
succinate + acceptor ⇌ fumarate + reduced acceptor

However, the oxidative TCA cycle (OTCA) still is present in green sulfur bacteria. The OTCA can assimilate acetate, however the OTCA appears to be incomplete in green sulfur bacteria due to the location and down regulation of the gene during phototrophic growth.^[8]

Mixotrophy

Green sulfur bacteria are obligate photoautotrophs: they cannot grow in the absence of light even if they are provided with organic matter.^[8]^[23] However they exhibit a form of mixotrophy where they can consume simple organic compounds in the presence of light and CO₂.^[8]

Nitrogen fixation

The majority of green sulfur bacteria are diazotrophs: they can reduce nitrogen to ammonia which is then used to synthesize amino acids.^[28]

References

^ Gibbons NE, Murray RGE. (1978). "Proposals Concerning the Higher Taxa of Bacteria". International Journal of Systematic Bacteriology. 28: 1–6. doi:10.1099/00207713-28-1-1.
^ Garrity GM, Holt JG. (2001). "Phylum BXI. Chlorobi phy. nov.". In Boone DR, Castenholz RW, Garrity GM. (eds.). Bergey's Manual of Systematic Bacteriology. Vol. 1 (The Archaea and the deeply branching and phototrophic Bacteria) (2nd ed.). New York, NY: Springer–Verlag. pp. 601–623.
^ Oren A, Garrity GM (2021). "Valid publication of the names of forty-two phyla of prokaryotes". Int J Syst Evol Microbiol. 71 (10): 5056. doi:10.1099/ijsem.0.005056. PMID 34694987. S2CID 239887308.
^ ^a ^b Bryant DA, Frigaard NU (November 2006). "Prokaryotic photosynthesis and phototrophy illuminated". Trends in Microbiology. 14 (11): 488–96. doi:10.1016/j.tim.2006.09.001. PMID 16997562.
^ Green BR (2003). Light-Harvesting Antennas in Photosynthesis. p. 8. ISBN 0792363353.
^ Kushkevych, Ivan; Procházka, Jiří; Gajdács, Márió; Rittmann, Simon K.-M. R.; Vítězová, Monika (2021-06-15). "Molecular Physiology of Anaerobic Phototrophic Purple and Green Sulfur Bacteria". International Journal of Molecular Sciences. 22 (12): 6398. doi:10.3390/ijms22126398. ISSN 1422-0067. PMC 8232776. PMID 34203823.
^ ^a ^b Sakurai H, Ogawa T, Shiga M, Inoue K (June 2010). "Inorganic sulfur oxidizing system in green sulfur bacteria". Photosynthesis Research. 104 (2–3): 163–76. doi:10.1007/s11120-010-9531-2. PMID 20143161. S2CID 1091791.
^ ^a ^b ^c ^d ^e ^f ^g Tang KH, Blankenship RE (November 2010). "Both forward and reverse TCA cycles operate in green sulfur bacteria". The Journal of Biological Chemistry. 285 (46): 35848–54. doi:10.1074/jbc.M110.157834. PMC 2975208. PMID 20650900.
^ Wahlund, Thomas (1993). "Nitrogen Fixation by the Thermophilic Green Sulfur Bacterium Chlorobium tepidum". Journal of Bacteriology. 175 (2): 474–478. doi:10.1128/jb.175.2.474-478.1993. PMC 196162. PMID 8093448.
^ Feng, Xueyang; Tang, Kuo-Hsiang; Blankenship, Robert E.; Tang, Yinjie J. (2010-12-10). "Metabolic Flux Analysis of the Mixotrophic Metabolisms in the Green Sulfur Bacterium Chlorobaculum tepidum*". Journal of Biological Chemistry. 285 (50): 39544–39550. doi:10.1074/jbc.M110.162958. ISSN 0021-9258. PMC 2998096. PMID 20937805.
^ "Green Sulfur Bacteria - an overview | ScienceDirect Topics". www.sciencedirect.com. Retrieved 2022-04-22.
^ Kushkevych, Ivan; Procházka, Jiří; Gajdács, Márió; Rittmann, Simon K.-M. R.; Vítězová, Monika (2021-06-15). "Molecular Physiology of Anaerobic Phototrophic Purple and Green Sulfur Bacteria". International Journal of Molecular Sciences. 22 (12): 6398. doi:10.3390/ijms22126398. ISSN 1422-0067. PMC 8232776. PMID 34203823.
^ John Wiley & Sons, Ltd, ed. (2001-05-30). eLS (1 ed.). Wiley. doi:10.1002/9780470015902.a0000458.pub2. ISBN 978-0-470-01617-6.
^ Kushkevych, Ivan; Procházka, Jiří; Gajdács, Márió; Rittmann, Simon K.-M. R.; Vítězová, Monika (2021-06-15). "Molecular Physiology of Anaerobic Phototrophic Purple and Green Sulfur Bacteria". International Journal of Molecular Sciences. 22 (12): 6398. doi:10.3390/ijms22126398. ISSN 1422-0067. PMC 8232776. PMID 34203823.
^ Marschall E, Jogler M, Hessge U, Overmann J (May 2010). "Large-scale distribution and activity patterns of an extremely low-light-adapted population of green sulfur bacteria in the Black Sea". Environmental Microbiology. 12 (5): 1348–62. doi:10.1111/j.1462-2920.2010.02178.x. PMID 20236170.
^ Beatty JT, Overmann J, Lince MT, Manske AK, Lang AS, Blankenship RE, Van Dover CL, Martinson TA, Plumley FG (June 2005). "An obligately photosynthetic bacterial anaerobe from a deep-sea hydrothermal vent". Proceedings of the National Academy of Sciences of the United States of America. 102 (26): 9306–10. Bibcode:2005PNAS..102.9306B. doi:10.1073/pnas.0503674102. PMC 1166624. PMID 15967984.
^ Yang, Shan-Hua; Lee, Sonny T. M.; Huang, Chang-Rung; Tseng, Ching-Hung; Chiang, Pei-Wen; Chen, Chung-Pin; Chen, Hsing-Ju; Tang, Sen-Lin (2016-02-26). "Prevalence of potential nitrogen-fixing, green sulfur bacteria in the skeleton of reef-building coral Isopora palifera". Limnology and Oceanography. 61 (3): 1078–1086. Bibcode:2016LimOc..61.1078Y. doi:10.1002/lno.10277. ISSN 0024-3590. S2CID 87463811.
^ Cai, Lin; Zhou, Guowei; Tian, Ren-Mao; Tong, Haoya; Zhang, Weipeng; Sun, Jin; Ding, Wei; Wong, Yue Him; Xie, James Y.; Qiu, Jian-Wen; Liu, Sheng (2017-08-24). "Metagenomic analysis reveals a green sulfur bacterium as a potential coral symbiont". Scientific Reports. 7 (1): 9320. Bibcode:2017NatSR...7.9320C. doi:10.1038/s41598-017-09032-4. ISSN 2045-2322. PMC 5571212. PMID 28839161.
^ Kushkevych, Ivan; Procházka, Jiří; Gajdács, Márió; Rittmann, Simon K.-M. R.; Vítězová, Monika (2021-06-15). "Molecular Physiology of Anaerobic Phototrophic Purple and Green Sulfur Bacteria". International Journal of Molecular Sciences. 22 (12): 6398. doi:10.3390/ijms22126398. ISSN 1422-0067. PMC 8232776. PMID 34203823.
^ See the All-Species Living Tree Project [1]. Data extracted from the "16S rRNA-based LTP release 123 (full tree)" (PDF). Silva Comprehensive Ribosomal RNA Database. Retrieved 2016-03-20.
^ ^a ^b ^c ^d ^e Bryantseva, Irina A.; Tarasov, Alexey L.; Kostrikina, Nadezhda A.; Gaisin, Vasil A.; Grouzdev, Denis S.; Gorlenko, Vladimir M. (2019-12-01). "Prosthecochloris marina sp. nov., a new green sulfur bacterium from the coastal zone of the South China Sea". Archives of Microbiology. 201 (10): 1399–1404. doi:10.1007/s00203-019-01707-y. ISSN 1432-072X. PMID 31338544. S2CID 198190182.
^ ^a ^b Hauska G, Schoedl T, Remigy H, Tsiotis G (October 2001). "The reaction center of green sulfur bacteria(1)". Biochimica et Biophysica Acta. 1507 (1–3): 260–77. doi:10.1016/S0005-2728(01)00200-6. PMID 11687219.
^ ^a ^b Ligrone, Roberto (2019). "Moving to the Light: The Evolution of Photosynthesis". In Roberto Ligrone (ed.). Biological Innovations that Built the World: A Four-billion-year Journey through Life and Earth History. Cham: Springer International Publishing. pp. 99–127. doi:10.1007/978-3-030-16057-9_4. ISBN 978-3-030-16057-9. S2CID 189992218. Retrieved 2021-01-29.
^ ^a ^b ^c ^d Frigaard, Niels-Ulrik; Dahl, Christiane (2008-01-01), Poole, Robert K. (ed.), "Sulfur Metabolism in Phototrophic Sulfur Bacteria", Advances in Microbial Physiology, vol. 54, Academic Press, pp. 103–200, retrieved 2022-04-22
^ van Gemerden, Hans (1986-10-01). "Production of elemental sulfur by green and purple sulfur bacteria". Archives of Microbiology. 146 (1): 52–56. doi:10.1007/BF00690158. ISSN 1432-072X. S2CID 30812886.
^ ^a ^b Gregersen, Lea; Bryant, Donald; Frigaard, Niels-Ulrik (2011). "Mechanisms and Evolution of Oxidative Sulfur Metabolism in Green Sulfur Bacteria". Frontiers in Microbiology. 2: 116. doi:10.3389/fmicb.2011.00116. ISSN 1664-302X. PMC 3153061. PMID 21833341.
^ ^a ^b Bar-Even, Arren; Noor, Elad; Milo, Ron (2012). "A survey of carbon fixation pathways through a quantitative lens". Journal of Experimental Botany. 63 (6): 2325–2342. doi:10.1093/jxb/err417. ISSN 1460-2431. PMID 22200662.
^ Madigan, Michael T. (1995). "Microbiology of Nitrogen Fixation by Anoxygenic Photosynthetic Bacteria". In Robert E. Blankenship; Michael T. Madigan; Carl E. Bauer (eds.). Anoxygenic Photosynthetic Bacteria. Advances in Photosynthesis and Respiration. Vol. 2. Dordrecht: Springer Netherlands. pp. 915–928. doi:10.1007/0-306-47954-0_42. ISBN 978-0-306-47954-0.

External links

"The Family Chlorobiaceae". The Prokaryotes. Archived from the original on November 17, 2003. Retrieved July 5, 2005.

[1] Gibbons NE, Murray RGE. (1978). "Proposals Concerning the Higher Taxa of Bacteria". International Journal of Systematic Bacteriology. 28: 1–6. doi:10.1099/00207713-28-1-1.

[2] Garrity GM, Holt JG. (2001). "Phylum BXI. Chlorobi phy. nov.". In Boone DR, Castenholz RW, Garrity GM. (eds.). Bergey's Manual of Systematic Bacteriology. Vol. 1 (The Archaea and the deeply branching and phototrophic Bacteria) (2nd ed.). New York, NY: Springer–Verlag. pp. 601–623.

[3] Oren A, Garrity GM (2021). "Valid publication of the names of forty-two phyla of prokaryotes". Int J Syst Evol Microbiol. 71 (10): 5056. doi:10.1099/ijsem.0.005056. PMID 34694987. S2CID 239887308.

[pmid16997562-4] Bryant DA, Frigaard NU (November 2006). "Prokaryotic photosynthesis and phototrophy illuminated". Trends in Microbiology. 14 (11): 488–96. doi:10.1016/j.tim.2006.09.001. PMID 16997562.

[beverleygreen-5] Green BR (2003). Light-Harvesting Antennas in Photosynthesis. p. 8. ISBN 0792363353.

[6] Kushkevych, Ivan; Procházka, Jiří; Gajdács, Márió; Rittmann, Simon K.-M. R.; Vítězová, Monika (2021-06-15). "Molecular Physiology of Anaerobic Phototrophic Purple and Green Sulfur Bacteria". International Journal of Molecular Sciences. 22 (12): 6398. doi:10.3390/ijms22126398. ISSN 1422-0067. PMC 8232776. PMID 34203823.

[pmid20143161-7] Sakurai H, Ogawa T, Shiga M, Inoue K (June 2010). "Inorganic sulfur oxidizing system in green sulfur bacteria". Photosynthesis Research. 104 (2–3): 163–76. doi:10.1007/s11120-010-9531-2. PMID 20143161. S2CID 1091791.

[pmid20650900-8] ^ ^a ^b ^c ^d ^e ^f ^g Tang KH, Blankenship RE (November 2010). "Both forward and reverse TCA cycles operate in green sulfur bacteria". The Journal of Biological Chemistry. 285 (46): 35848–54. doi:10.1074/jbc.M110.157834. PMC 2975208. PMID 20650900.

[9] Wahlund, Thomas (1993). "Nitrogen Fixation by the Thermophilic Green Sulfur Bacterium Chlorobium tepidum". Journal of Bacteriology. 175 (2): 474–478. doi:10.1128/jb.175.2.474-478.1993. PMC 196162. PMID 8093448.

[10] Feng, Xueyang; Tang, Kuo-Hsiang; Blankenship, Robert E.; Tang, Yinjie J. (2010-12-10). "Metabolic Flux Analysis of the Mixotrophic Metabolisms in the Green Sulfur Bacterium Chlorobaculum tepidum*". Journal of Biological Chemistry. 285 (50): 39544–39550. doi:10.1074/jbc.M110.162958. ISSN 0021-9258. PMC 2998096. PMID 20937805.

[11] "Green Sulfur Bacteria - an overview | ScienceDirect Topics". www.sciencedirect.com. Retrieved 2022-04-22.

[12] Kushkevych, Ivan; Procházka, Jiří; Gajdács, Márió; Rittmann, Simon K.-M. R.; Vítězová, Monika (2021-06-15). "Molecular Physiology of Anaerobic Phototrophic Purple and Green Sulfur Bacteria". International Journal of Molecular Sciences. 22 (12): 6398. doi:10.3390/ijms22126398. ISSN 1422-0067. PMC 8232776. PMID 34203823.

[13] John Wiley & Sons, Ltd, ed. (2001-05-30). eLS (1 ed.). Wiley. doi:10.1002/9780470015902.a0000458.pub2. ISBN 978-0-470-01617-6.

[14] Kushkevych, Ivan; Procházka, Jiří; Gajdács, Márió; Rittmann, Simon K.-M. R.; Vítězová, Monika (2021-06-15). "Molecular Physiology of Anaerobic Phototrophic Purple and Green Sulfur Bacteria". International Journal of Molecular Sciences. 22 (12): 6398. doi:10.3390/ijms22126398. ISSN 1422-0067. PMC 8232776. PMID 34203823.

[pmid20236170-15] Marschall E, Jogler M, Hessge U, Overmann J (May 2010). "Large-scale distribution and activity patterns of an extremely low-light-adapted population of green sulfur bacteria in the Black Sea". Environmental Microbiology. 12 (5): 1348–62. doi:10.1111/j.1462-2920.2010.02178.x. PMID 20236170.

[pmid15967984-16] Beatty JT, Overmann J, Lince MT, Manske AK, Lang AS, Blankenship RE, Van Dover CL, Martinson TA, Plumley FG (June 2005). "An obligately photosynthetic bacterial anaerobe from a deep-sea hydrothermal vent". Proceedings of the National Academy of Sciences of the United States of America. 102 (26): 9306–10. Bibcode:2005PNAS..102.9306B. doi:10.1073/pnas.0503674102. PMC 1166624. PMID 15967984.

[17] Yang, Shan-Hua; Lee, Sonny T. M.; Huang, Chang-Rung; Tseng, Ching-Hung; Chiang, Pei-Wen; Chen, Chung-Pin; Chen, Hsing-Ju; Tang, Sen-Lin (2016-02-26). "Prevalence of potential nitrogen-fixing, green sulfur bacteria in the skeleton of reef-building coral Isopora palifera". Limnology and Oceanography. 61 (3): 1078–1086. Bibcode:2016LimOc..61.1078Y. doi:10.1002/lno.10277. ISSN 0024-3590. S2CID 87463811.

[18] Cai, Lin; Zhou, Guowei; Tian, Ren-Mao; Tong, Haoya; Zhang, Weipeng; Sun, Jin; Ding, Wei; Wong, Yue Him; Xie, James Y.; Qiu, Jian-Wen; Liu, Sheng (2017-08-24). "Metagenomic analysis reveals a green sulfur bacterium as a potential coral symbiont". Scientific Reports. 7 (1): 9320. Bibcode:2017NatSR...7.9320C. doi:10.1038/s41598-017-09032-4. ISSN 2045-2322. PMC 5571212. PMID 28839161.

[19] Kushkevych, Ivan; Procházka, Jiří; Gajdács, Márió; Rittmann, Simon K.-M. R.; Vítězová, Monika (2021-06-15). "Molecular Physiology of Anaerobic Phototrophic Purple and Green Sulfur Bacteria". International Journal of Molecular Sciences. 22 (12): 6398. doi:10.3390/ijms22126398. ISSN 1422-0067. PMC 8232776. PMID 34203823.

[20] See the All-Species Living Tree Project [1]. Data extracted from the "16S rRNA-based LTP release 123 (full tree)" (PDF). Silva Comprehensive Ribosomal RNA Database. Retrieved 2016-03-20.

[:0-21] Bryantseva, Irina A.; Tarasov, Alexey L.; Kostrikina, Nadezhda A.; Gaisin, Vasil A.; Grouzdev, Denis S.; Gorlenko, Vladimir M. (2019-12-01). "Prosthecochloris marina sp. nov., a new green sulfur bacterium from the coastal zone of the South China Sea". Archives of Microbiology. 201 (10): 1399–1404. doi:10.1007/s00203-019-01707-y. ISSN 1432-072X. PMID 31338544. S2CID 198190182.

[Hauska2001-22] Hauska G, Schoedl T, Remigy H, Tsiotis G (October 2001). "The reaction center of green sulfur bacteria(1)". Biochimica et Biophysica Acta. 1507 (1–3): 260–77. doi:10.1016/S0005-2728(01)00200-6. PMID 11687219.

[Ligrone2019-23] Ligrone, Roberto (2019). "Moving to the Light: The Evolution of Photosynthesis". In Roberto Ligrone (ed.). Biological Innovations that Built the World: A Four-billion-year Journey through Life and Earth History. Cham: Springer International Publishing. pp. 99–127. doi:10.1007/978-3-030-16057-9_4. ISBN 978-3-030-16057-9. S2CID 189992218. Retrieved 2021-01-29.

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[:2-26] Gregersen, Lea; Bryant, Donald; Frigaard, Niels-Ulrik (2011). "Mechanisms and Evolution of Oxidative Sulfur Metabolism in Green Sulfur Bacteria". Frontiers in Microbiology. 2: 116. doi:10.3389/fmicb.2011.00116. ISSN 1664-302X. PMC 3153061. PMID 21833341.

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@@ Line 4: / Line 4: @@
 | image_caption = Green sulfur bacteria in a [[Winogradsky column]]
 | display_parents = 3
-| grandparent_authority = Iino et al. 2021<ref>{{cite journal | vauthors = Oren A, Garrity GM | title = Valid publication of the names of forty-two phyla of prokaryotes | journal = Int J Syst Evol Microbiol | year = 2021 | volume = 71 | issue = 10 | pages = 5056 | doi = 10.1099/ijsem.0.005056 | pmid = 34694987 | url = https://www.microbiologyresearch.org/pubmed/content/journal/ijsem/10.1099/ijsem.0.005056}}</ref>
+| grandparent_authority = Iino et al. 2021<ref>{{cite journal | vauthors = Oren A, Garrity GM | title = Valid publication of the names of forty-two phyla of prokaryotes | journal = Int J Syst Evol Microbiol | year = 2021 | volume = 71 | issue = 10 | pages = 5056 | doi = 10.1099/ijsem.0.005056 | pmid = 34694987 | s2cid = 239887308 | url = https://www.microbiologyresearch.org/pubmed/content/journal/ijsem/10.1099/ijsem.0.005056}}</ref>
 | parent_authority = Garrity and Holt 2001<ref>{{cite book | vauthors = Garrity GM, ((Holt JG.)) | chapter = Phylum BXI. ''Chlorobi'' phy. nov. | veditors = Boone DR, Castenholz RW, ((Garrity GM.)) | title = Bergey's Manual of Systematic Bacteriology | edition = 2nd | volume = 1 (The Archaea and the deeply branching and phototrophic Bacteria) | publisher = Springer–Verlag | location = New York, NY | year = 2001 | pages = 601–623}}</ref>
 | taxon = Chlorobiales
@@ Line 40: / Line 40: @@
 The '''green sulfur bacteria''' are a [[phylum]] of obligately [[anaerobic organism|anaerobic]] [[photoautotrophic]] [[bacteria]] that metabolize sulfur.<ref name=pmid16997562>{{cite journal | vauthors = Bryant DA, Frigaard NU | title = Prokaryotic photosynthesis and phototrophy illuminated | journal = Trends in Microbiology | volume = 14 | issue = 11 | pages = 488–96 | date = November 2006 | pmid = 16997562 | doi = 10.1016/j.tim.2006.09.001 }}</ref>
-Green sulfur bacteria are [[motility|nonmotile]] (except ''Chloroherpeton thalassium'', which may glide) and capable of [[anoxygenic photosynthesis]].<ref name=pmid16997562/><ref name=beverleygreen>{{Cite book|title = Light-Harvesting Antennas in Photosynthesis|last = Green|first = Beverley R. | name-list-style = vanc |year = 2003|isbn = 0792363353|pages = 8}}</ref> They live in anaerobic aquatic environments.<ref>{{Cite journal |last=Kushkevych |first=Ivan |last2=Procházka |first2=Jiří |last3=Gajdács |first3=Márió |last4=Rittmann |first4=Simon K.-M. R. |last5=Vítězová |first5=Monika |date=2021-06-15 |title=Molecular Physiology of Anaerobic Phototrophic Purple and Green Sulfur Bacteria |url=https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8232776/ |journal=International Journal of Molecular Sciences |volume=22 |issue=12 |pages=6398 |doi=10.3390/ijms22126398 |issn=1422-0067 |pmc=8232776 |pmid=34203823}}</ref> In contrast to plants, green sulfur bacteria mainly use sulfide ions as electron donors.<ref name=pmid20143161>{{cite journal | vauthors = Sakurai H, Ogawa T, Shiga M, Inoue K | title = Inorganic sulfur oxidizing system in green sulfur bacteria | journal = Photosynthesis Research | volume = 104 | issue = 2–3 | pages = 163–76 | date = June 2010 | pmid = 20143161 | doi = 10.1007/s11120-010-9531-2 | s2cid = 1091791 }}</ref> They are [[autotroph]]s that utilize the [[reverse Krebs cycle|reverse tricarboxylic acid cycle]] to perform [[carbon fixation]].<ref name=pmid20650900>{{cite journal | vauthors = Tang KH, Blankenship RE | title = Both forward and reverse TCA cycles operate in green sulfur bacteria | journal = The Journal of Biological Chemistry | volume = 285 | issue = 46 | pages = 35848–54 | date = November 2010 | pmid = 20650900 | pmc = 2975208 | doi = 10.1074/jbc.M110.157834 | doi-access = free }}</ref>  They are also mixotrophs and reduce nitrogen.<ref>{{Cite journal |last=Wahlund |first=Thomas |date=1993 |title=Nitrogen Fixation by the Thermophilic Green Sulfur Bacterium Chlorobium tepidum |url=https://www.ncbi.nlm.nih.gov/pmc/articles/PMC196162/pdf/jbacter00044-0180.pdf |journal=Journal of Bacteriology |volume=175 |pages=474-478}}</ref><ref>{{Cite journal |last=Feng |first=Xueyang |last2=Tang |first2=Kuo-Hsiang |last3=Blankenship |first3=Robert E. |last4=Tang |first4=Yinjie J. |date=2010-12-10 |title=Metabolic Flux Analysis of the Mixotrophic Metabolisms in the Green Sulfur Bacterium Chlorobaculum tepidum* |url=https://www.jbc.org/article/S0021-9258(20)60650-0/abstract |journal=Journal of Biological Chemistry |language=English |volume=285 |issue=50 |pages=39544–39550 |doi=10.1074/jbc.M110.162958 |issn=0021-9258 |pmid=20937805}}</ref>
+Green sulfur bacteria are [[motility|nonmotile]] (except ''Chloroherpeton thalassium'', which may glide) and capable of [[anoxygenic photosynthesis]].<ref name=pmid16997562/><ref name=beverleygreen>{{Cite book|title = Light-Harvesting Antennas in Photosynthesis|last = Green|first = Beverley R. | name-list-style = vanc |year = 2003|isbn = 0792363353|pages = 8}}</ref> They live in anaerobic aquatic environments.<ref>{{Cite journal |last1=Kushkevych |first1=Ivan |last2=Procházka |first2=Jiří |last3=Gajdács |first3=Márió |last4=Rittmann |first4=Simon K.-M. R. |last5=Vítězová |first5=Monika |date=2021-06-15 |title=Molecular Physiology of Anaerobic Phototrophic Purple and Green Sulfur Bacteria |journal=International Journal of Molecular Sciences |volume=22 |issue=12 |pages=6398 |doi=10.3390/ijms22126398 |issn=1422-0067 |pmc=8232776 |pmid=34203823|doi-access=free }}</ref> In contrast to plants, green sulfur bacteria mainly use sulfide ions as electron donors.<ref name=pmid20143161>{{cite journal | vauthors = Sakurai H, Ogawa T, Shiga M, Inoue K | title = Inorganic sulfur oxidizing system in green sulfur bacteria | journal = Photosynthesis Research | volume = 104 | issue = 2–3 | pages = 163–76 | date = June 2010 | pmid = 20143161 | doi = 10.1007/s11120-010-9531-2 | s2cid = 1091791 }}</ref> They are [[autotroph]]s that utilize the [[reverse Krebs cycle|reverse tricarboxylic acid cycle]] to perform [[carbon fixation]].<ref name=pmid20650900>{{cite journal | vauthors = Tang KH, Blankenship RE | title = Both forward and reverse TCA cycles operate in green sulfur bacteria | journal = The Journal of Biological Chemistry | volume = 285 | issue = 46 | pages = 35848–54 | date = November 2010 | pmid = 20650900 | pmc = 2975208 | doi = 10.1074/jbc.M110.157834 | doi-access = free }}</ref>  They are also mixotrophs and reduce nitrogen.<ref>{{Cite journal |last=Wahlund |first=Thomas |date=1993 |title=Nitrogen Fixation by the Thermophilic Green Sulfur Bacterium Chlorobium tepidum |journal=Journal of Bacteriology |volume=175 |issue=2 |pages=474–478|doi=10.1128/jb.175.2.474-478.1993 |pmid=8093448 |pmc=196162 }}</ref><ref>{{Cite journal |last1=Feng |first1=Xueyang |last2=Tang |first2=Kuo-Hsiang |last3=Blankenship |first3=Robert E. |last4=Tang |first4=Yinjie J. |date=2010-12-10 |title=Metabolic Flux Analysis of the Mixotrophic Metabolisms in the Green Sulfur Bacterium Chlorobaculum tepidum* |url=https://www.jbc.org/article/S0021-9258(20)60650-0/abstract |journal=Journal of Biological Chemistry |language=English |volume=285 |issue=50 |pages=39544–39550 |doi=10.1074/jbc.M110.162958 |issn=0021-9258 |pmid=20937805|pmc=2998096 |doi-access=free }}</ref>
 ==Characteristics==
-Green sulfur bacteria are [[Gram-negative bacteria|gram-negative]] rod or spherical shaped bacteria. Some types of green sulfur bacteria have gas vacuoles that allow for movement. They are photolithoautotrophs, and use light energy and reduced sulfur compounds as the electron source.<ref>{{Cite web |title=Green Sulfur Bacteria - an overview {{!}} ScienceDirect Topics |url=https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/green-sulfur-bacteria#:~:text=Green%20sulfur%20bacteria%20such%20as,and%20are%20strictly%20anaerobic%20photoautotrophs. |access-date=2022-04-22 |website=www.sciencedirect.com}}</ref> Electron donors include  H<sub>2</sub>, H<sub>2</sub>S, S. The major photosynthetic pigment in these bacteria is [[Bacteriochlorophyll|Bacteriochlorophylls]] ''c'' or ''d'' in green species and ''e'' in brown species, and is located in the chlorosomes and plasma membranes.<ref>{{Cite journal |last=Kushkevych |first=Ivan |last2=Procházka |first2=Jiří |last3=Gajdács |first3=Márió |last4=Rittmann |first4=Simon K.-M. R. |last5=Vítězová |first5=Monika |date=2021-06-15 |title=Molecular Physiology of Anaerobic Phototrophic Purple and Green Sulfur Bacteria |url=https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8232776/ |journal=International Journal of Molecular Sciences |volume=22 |issue=12 |pages=6398 |doi=10.3390/ijms22126398 |issn=1422-0067 |pmc=8232776 |pmid=34203823}}</ref> [[Chlorosome|Chlorosomes]] are a unique feature that allow them to capture light in low-light conditions.<ref>{{Cite book |url=https://onlinelibrary.wiley.com/doi/book/10.1002/047001590X |title=eLS |date=2001-05-30 |publisher=Wiley |isbn=978-0-470-01617-6 |editor-last=John Wiley & Sons, Ltd |edition=1 |language=en |doi=10.1002/9780470015902.a0000458.pub2}}</ref>
+Green sulfur bacteria are [[Gram-negative bacteria|gram-negative]] rod or spherical shaped bacteria. Some types of green sulfur bacteria have gas vacuoles that allow for movement. They are photolithoautotrophs, and use light energy and reduced sulfur compounds as the electron source.<ref>{{Cite web |title=Green Sulfur Bacteria - an overview {{!}} ScienceDirect Topics |url=https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/green-sulfur-bacteria#:~:text=Green%20sulfur%20bacteria%20such%20as,and%20are%20strictly%20anaerobic%20photoautotrophs. |access-date=2022-04-22 |website=www.sciencedirect.com}}</ref> Electron donors include  H<sub>2</sub>, H<sub>2</sub>S, S. The major photosynthetic pigment in these bacteria is [[Bacteriochlorophyll|Bacteriochlorophylls]] ''c'' or ''d'' in green species and ''e'' in brown species, and is located in the chlorosomes and plasma membranes.<ref>{{Cite journal |last1=Kushkevych |first1=Ivan |last2=Procházka |first2=Jiří |last3=Gajdács |first3=Márió |last4=Rittmann |first4=Simon K.-M. R. |last5=Vítězová |first5=Monika |date=2021-06-15 |title=Molecular Physiology of Anaerobic Phototrophic Purple and Green Sulfur Bacteria |journal=International Journal of Molecular Sciences |volume=22 |issue=12 |pages=6398 |doi=10.3390/ijms22126398 |issn=1422-0067 |pmc=8232776 |pmid=34203823|doi-access=free }}</ref> [[Chlorosome|Chlorosomes]] are a unique feature that allow them to capture light in low-light conditions.<ref>{{Cite book |url=https://onlinelibrary.wiley.com/doi/book/10.1002/047001590X |title=eLS |date=2001-05-30 |publisher=Wiley |isbn=978-0-470-01617-6 |editor-last=John Wiley & Sons, Ltd |edition=1 |language=en |doi=10.1002/9780470015902.a0000458.pub2}}</ref>
 ==Habitat==
-The majority of green sulfur bacteria are [[Mesophile|mesophilic]], preferring moderate temperatures, and all live in aquatic environments. They require anaerobic conditions and reduced sulfur; they are usually found in the top millimeters of sediment. They are capable of photosynthesis in low light conditions. <ref>{{Cite journal |last=Kushkevych |first=Ivan |last2=Procházka |first2=Jiří |last3=Gajdács |first3=Márió |last4=Rittmann |first4=Simon K.-M. R. |last5=Vítězová |first5=Monika |date=2021-06-15 |title=Molecular Physiology of Anaerobic Phototrophic Purple and Green Sulfur Bacteria |url=https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8232776/ |journal=International Journal of Molecular Sciences |volume=22 |issue=12 |pages=6398 |doi=10.3390/ijms22126398 |issn=1422-0067 |pmc=8232776 |pmid=34203823}}</ref>
+The majority of green sulfur bacteria are [[Mesophile|mesophilic]], preferring moderate temperatures, and all live in aquatic environments. They require anaerobic conditions and reduced sulfur; they are usually found in the top millimeters of sediment. They are capable of photosynthesis in low light conditions. <ref>{{Cite journal |last1=Kushkevych |first1=Ivan |last2=Procházka |first2=Jiří |last3=Gajdács |first3=Márió |last4=Rittmann |first4=Simon K.-M. R. |last5=Vítězová |first5=Monika |date=2021-06-15 |title=Molecular Physiology of Anaerobic Phototrophic Purple and Green Sulfur Bacteria |journal=International Journal of Molecular Sciences |volume=22 |issue=12 |pages=6398 |doi=10.3390/ijms22126398 |issn=1422-0067 |pmc=8232776 |pmid=34203823|doi-access=free }}</ref>
 The [[Black Sea]], an extremely anoxic environment, was found to house a large population of green sulfur bacteria at about 100 m depth.  Due to the lack of light available in this region of the sea, most bacteria were photosynthetically inactive.  The photosynthetic activity detected in the sulfide [[chemocline]] suggests that the bacteria need very little energy for cellular maintenance.<ref name="pmid20236170">{{cite journal |vauthors=Marschall E, Jogler M, Hessge U, Overmann J |date=May 2010 |title=Large-scale distribution and activity patterns of an extremely low-light-adapted population of green sulfur bacteria in the Black Sea |journal=Environmental Microbiology |volume=12 |issue=5 |pages=1348–62 |doi=10.1111/j.1462-2920.2010.02178.x |pmid=20236170}}</ref>
@@ Line 53: / Line 53: @@
 A species of green sulfur bacteria has been found living near a [[black smoker]] off the coast of [[Mexico]] at a depth of 2,500 m in the [[Pacific Ocean]].  At this depth, the bacterium, designated GSB1, lives off the dim glow of the thermal vent since no sunlight can penetrate to that depth.<ref name=pmid15967984>{{cite journal | vauthors = Beatty JT, Overmann J, Lince MT, Manske AK, Lang AS, Blankenship RE, Van Dover CL, Martinson TA, Plumley FG | title = An obligately photosynthetic bacterial anaerobe from a deep-sea hydrothermal vent | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 102 | issue = 26 | pages = 9306–10 | date = June 2005 | pmid = 15967984 | pmc = 1166624 | doi = 10.1073/pnas.0503674102 | bibcode = 2005PNAS..102.9306B | doi-access = free }}</ref>
-Green sulfur bacteria has also been found living on coral reef colonies in Taiwan, they make up the majority of a "green layer" on these colonies.  They likely play a role in the coral system, and there could be a symbiotic relationship between the bacteria and the coral host.'''<ref>{{Cite journal|last=Yang|first=Shan-Hua|last2=Lee|first2=Sonny T. M.|last3=Huang|first3=Chang-Rung|last4=Tseng|first4=Ching-Hung|last5=Chiang|first5=Pei-Wen|last6=Chen|first6=Chung-Pin|last7=Chen|first7=Hsing-Ju|last8=Tang|first8=Sen-Lin|date=2016-02-26|title=Prevalence of potential nitrogen-fixing, green sulfur bacteria in the skeleton of reef-building coral Isopora palifera|url=https://aslopubs.onlinelibrary.wiley.com/doi/pdfdirect/10.1002/lno.10277|journal=Limnology and Oceanography|volume=61|issue=3|pages=1078–1086|doi=10.1002/lno.10277|issn=0024-3590}}</ref>''' The coral could provide an anaerobic environment and  a source of carbon for the bacteria. The bacteria can provide nutrients and detoxify the coral by oxidizing sulfide.<ref>{{Cite journal |last=Cai |first=Lin |last2=Zhou |first2=Guowei |last3=Tian |first3=Ren-Mao |last4=Tong |first4=Haoya |last5=Zhang |first5=Weipeng |last6=Sun |first6=Jin |last7=Ding |first7=Wei |last8=Wong |first8=Yue Him |last9=Xie |first9=James Y. |last10=Qiu |first10=Jian-Wen |last11=Liu |first11=Sheng |date=2017-08-24 |title=Metagenomic analysis reveals a green sulfur bacterium as a potential coral symbiont |url=https://www.nature.com/articles/s41598-017-09032-4 |journal=Scientific Reports |language=en |volume=7 |issue=1 |pages=9320 |doi=10.1038/s41598-017-09032-4 |issn=2045-2322}}</ref>
+Green sulfur bacteria has also been found living on coral reef colonies in Taiwan, they make up the majority of a "green layer" on these colonies.  They likely play a role in the coral system, and there could be a symbiotic relationship between the bacteria and the coral host.'''<ref>{{Cite journal|last1=Yang|first1=Shan-Hua|last2=Lee|first2=Sonny T. M.|last3=Huang|first3=Chang-Rung|last4=Tseng|first4=Ching-Hung|last5=Chiang|first5=Pei-Wen|last6=Chen|first6=Chung-Pin|last7=Chen|first7=Hsing-Ju|last8=Tang|first8=Sen-Lin|date=2016-02-26|title=Prevalence of potential nitrogen-fixing, green sulfur bacteria in the skeleton of reef-building coral Isopora palifera|url=https://aslopubs.onlinelibrary.wiley.com/doi/pdfdirect/10.1002/lno.10277|journal=Limnology and Oceanography|volume=61|issue=3|pages=1078–1086|doi=10.1002/lno.10277|bibcode=2016LimOc..61.1078Y|s2cid=87463811|issn=0024-3590}}</ref>''' The coral could provide an anaerobic environment and  a source of carbon for the bacteria. The bacteria can provide nutrients and detoxify the coral by oxidizing sulfide.<ref>{{Cite journal |last1=Cai |first1=Lin |last2=Zhou |first2=Guowei |last3=Tian |first3=Ren-Mao |last4=Tong |first4=Haoya |last5=Zhang |first5=Weipeng |last6=Sun |first6=Jin |last7=Ding |first7=Wei |last8=Wong |first8=Yue Him |last9=Xie |first9=James Y. |last10=Qiu |first10=Jian-Wen |last11=Liu |first11=Sheng |date=2017-08-24 |title=Metagenomic analysis reveals a green sulfur bacterium as a potential coral symbiont |journal=Scientific Reports |language=en |volume=7 |issue=1 |pages=9320 |doi=10.1038/s41598-017-09032-4 |pmid=28839161 |pmc=5571212 |bibcode=2017NatSR...7.9320C |issn=2045-2322}}</ref>
-One type of green sulfur bacteria, Chlorobium tepidum, has been found in sulfur springs. These organisms are thermophilic, unlike most other green sulfur bacteria.<ref>{{Cite journal |last=Kushkevych |first=Ivan |last2=Procházka |first2=Jiří |last3=Gajdács |first3=Márió |last4=Rittmann |first4=Simon K.-M. R. |last5=Vítězová |first5=Monika |date=2021-06-15 |title=Molecular Physiology of Anaerobic Phototrophic Purple and Green Sulfur Bacteria |url=https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8232776/ |journal=International Journal of Molecular Sciences |volume=22 |issue=12 |pages=6398 |doi=10.3390/ijms22126398 |issn=1422-0067 |pmc=8232776 |pmid=34203823}}</ref>
+One type of green sulfur bacteria, Chlorobium tepidum, has been found in sulfur springs. These organisms are thermophilic, unlike most other green sulfur bacteria.<ref>{{Cite journal |last1=Kushkevych |first1=Ivan |last2=Procházka |first2=Jiří |last3=Gajdács |first3=Márió |last4=Rittmann |first4=Simon K.-M. R. |last5=Vítězová |first5=Monika |date=2021-06-15 |title=Molecular Physiology of Anaerobic Phototrophic Purple and Green Sulfur Bacteria |journal=International Journal of Molecular Sciences |volume=22 |issue=12 |pages=6398 |doi=10.3390/ijms22126398 |issn=1422-0067 |pmc=8232776 |pmid=34203823|doi-access=free }}</ref>
 ==Phylogeny==
@@ Line 103: / Line 103: @@
 === Specific characteristics of genera ===
-Green sulfur bacteria are family Chlorobiaceae. There are four genera; ''Chloroherpeton'', ''Prosthecochloris'', ''Chlorobium'' and ''Chlorobaculum''. Characteristics used to distinguish between these genera include some metabolic properties, pigments, cell morphology and absorption spectra. However, it is difficult to distinguish these properties and therefore the taxonomic division is sometimes unclear.<ref name=":0">{{Cite journal |last=Bryantseva |first=Irina A. |last2=Tarasov |first2=Alexey L. |last3=Kostrikina |first3=Nadezhda A. |last4=Gaisin |first4=Vasil A. |last5=Grouzdev |first5=Denis S. |last6=Gorlenko |first6=Vladimir M. |date=2019-12-01 |title=Prosthecochloris marina sp. nov., a new green sulfur bacterium from the coastal zone of the South China Sea |url=https://doi.org/10.1007/s00203-019-01707-y |journal=Archives of Microbiology |language=en |volume=201 |issue=10 |pages=1399–1404 |doi=10.1007/s00203-019-01707-y |issn=1432-072X}}</ref>
+Green sulfur bacteria are family Chlorobiaceae. There are four genera; ''Chloroherpeton'', ''Prosthecochloris'', ''Chlorobium'' and ''Chlorobaculum''. Characteristics used to distinguish between these genera include some metabolic properties, pigments, cell morphology and absorption spectra. However, it is difficult to distinguish these properties and therefore the taxonomic division is sometimes unclear.<ref name=":0">{{Cite journal |last1=Bryantseva |first1=Irina A. |last2=Tarasov |first2=Alexey L. |last3=Kostrikina |first3=Nadezhda A. |last4=Gaisin |first4=Vasil A. |last5=Grouzdev |first5=Denis S. |last6=Gorlenko |first6=Vladimir M. |date=2019-12-01 |title=Prosthecochloris marina sp. nov., a new green sulfur bacterium from the coastal zone of the South China Sea |url=https://doi.org/10.1007/s00203-019-01707-y |journal=Archives of Microbiology |language=en |volume=201 |issue=10 |pages=1399–1404 |doi=10.1007/s00203-019-01707-y |pmid=31338544 |s2cid=198190182 |issn=1432-072X}}</ref>
 Generally, ''Chlorobium'' are rod or vibroid shaped and some species contain gas vesicles. They can develop as single or aggregate cells. They can be green or dark brown. The green strains use photosynthetic pigments Bchl ''c'' or ''d'' with chlorobactene carotenoids and the brown strains use photosynthetic pigment  Bchl ''e'' with isorenieratene carotenoids. Low amounts of salt are required for growth.<ref name=":0" />
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 The green sulfur bacteria use a Type I reaction center for photosynthesis. Type I reaction centers are the bacterial [[Homology (biology)|homologue]] of [[photosystem I]] (PSI) in plants and [[cyanobacteria]]. The GSB reaction centers contain [[bacteriochlorophyll]] a and are known as '''P840''' reaction centers due to the excitation wavelength of 840&nbsp;nm that powers the flow of electrons. In green sulfur bacteria the reaction center is associated with a large antena complex called the [[chlorosome]] that captures and funnels light energy to the reaction center. The chlorosomes have a peak absorption in the [[far red]] region of the spectrum between 720-750&nbsp;nm because they contain bacteriochlorophyll c, d and e.<ref name=Hauska2001>{{cite journal | vauthors = Hauska G, Schoedl T, Remigy H, Tsiotis G | title = The reaction center of green sulfur bacteria(1) | journal = Biochimica et Biophysica Acta | volume = 1507 | issue = 1–3 | pages = 260–77 | date = October 2001 | pmid = 11687219 | doi = 10.1016/S0005-2728(01)00200-6 | doi-access = free }}</ref> A protein complex called the [[Fenna-Matthews-Olson complex]] (FMO) is physically located between the chlorosomes and the P840 RC. The FMO complex helps efficiently transfer the energy absorbed by the antena to the reaction center.
-PSI and Type I reaction centers are able to reduce [[ferredoxin]] (Fd), a strong reductant that can be used to fix {{chem|CO|2}} and reduce [[NADPH]]. Once the reaction center (RC) has given an electron to Fd it becomes an oxidizing agent (P840<sup>+</sup>) with a [[reduction potential]] of around +300 mV. While this is not positive enough to strip electrons from water to synthesize {{chem|O|2}} ({{chem|E|''0''}} = +820 mV), it can accept electrons from other sources like {{chem|H|2|S}}, [[thiosulphate]] or {{chem|Fe|2+}} ions.<ref name=Ligrone2019>{{Cite book| publisher = Springer International Publishing| isbn = 978-3-030-16057-9| pages = 99–127| editor = Roberto Ligrone | last = Ligrone| first = Roberto| title = Biological Innovations that Built the World: A Four-billion-year Journey through Life and Earth History| chapter = Moving to the Light: The Evolution of Photosynthesis| location = Cham| access-date = 2021-01-29| date = 2019| doi = 10.1007/978-3-030-16057-9_4| chapter-url = https://doi.org/10.1007/978-3-030-16057-9_4}}</ref> This transport of electrons from donors like {{chem|H|2|S}} to the acceptor Fd is called linear electron flow or linear electron transport. The oxidation of sulfide ions leads to the production of sulfur as a waste product that accumulates as globules on the extracellular side of the membrane. These globules of sulfur give green sulfur bacteria their name. When sulfide is depleted, the sulfur globules are consumed and further oxidized to sulfate.  However, the pathway of sulfur oxidation is not well-understood.<ref name=pmid20143161/>
+PSI and Type I reaction centers are able to reduce [[ferredoxin]] (Fd), a strong reductant that can be used to fix {{chem|CO|2}} and reduce [[NADPH]]. Once the reaction center (RC) has given an electron to Fd it becomes an oxidizing agent (P840<sup>+</sup>) with a [[reduction potential]] of around +300 mV. While this is not positive enough to strip electrons from water to synthesize {{chem|O|2}} ({{chem|E|''0''}} = +820 mV), it can accept electrons from other sources like {{chem|H|2|S}}, [[thiosulphate]] or {{chem|Fe|2+}} ions.<ref name=Ligrone2019>{{Cite book| publisher = Springer International Publishing| isbn = 978-3-030-16057-9| pages = 99–127| editor = Roberto Ligrone | last = Ligrone| first = Roberto| title = Biological Innovations that Built the World: A Four-billion-year Journey through Life and Earth History| chapter = Moving to the Light: The Evolution of Photosynthesis| location = Cham| access-date = 2021-01-29| date = 2019| doi = 10.1007/978-3-030-16057-9_4| s2cid = 189992218| chapter-url = https://doi.org/10.1007/978-3-030-16057-9_4}}</ref> This transport of electrons from donors like {{chem|H|2|S}} to the acceptor Fd is called linear electron flow or linear electron transport. The oxidation of sulfide ions leads to the production of sulfur as a waste product that accumulates as globules on the extracellular side of the membrane. These globules of sulfur give green sulfur bacteria their name. When sulfide is depleted, the sulfur globules are consumed and further oxidized to sulfate.  However, the pathway of sulfur oxidation is not well-understood.<ref name=pmid20143161/>
 Instead of passing the electrons onto Fd, the Fe-S clusters in the P840 reaction center can transfer the electrons to [[menaquinone]] (MQ:{{chem|MQH|2}}) which returns the electrons to the P840<sup>+</sup> via an [[electron transport chain]] (ETC). On the way back to the RC the electrons from MQH2 pass through a cytochrome bc<sub>1</sub> complex (similar to the [[complex III]] of mitochondria) that pumps {{chem|H|+}} ions across the membrane. The [[electrochemical potential]] of the protons across the membrane is used to synthesize [[Adenosine triphosphate|ATP]] by the F<sub>o</sub>F<sub>1</sub> [[ATP synthase]]. This cyclic electron transport is responsible for converting light energy into cellular energy in the form of ATP.<ref name="Hauska2001" />
 === Sulfur metabolism ===
-Green sulfur bacteria oxidize inorganic sulfur compounds to use as electron donors for anaerobic photosynthesis, specifically in carbon dioxide fixation. They usually prefer to utilize sulfide over other sulfur compounds as an electron donor, however they can utilize thiosulfate or H<sub>2</sub>.<ref name=":1">{{Citation |last=Frigaard |first=Niels-Ulrik |title=Sulfur Metabolism in Phototrophic Sulfur Bacteria |date=2008-01-01 |url=https://www.sciencedirect.com/science/article/pii/S0065291108000027 |work=Advances in Microbial Physiology |volume=54 |pages=103–200 |editor-last=Poole |editor-first=Robert K. |publisher=Academic Press |language=en |access-date=2022-04-22 |last2=Dahl |first2=Christiane}}</ref> The intermediate is usually sulfur, which is deposited outside of the cell,<ref>{{Cite journal |last=van Gemerden |first=Hans |date=1986-10-01 |title=Production of elemental sulfur by green and purple sulfur bacteria |url=https://doi.org/10.1007/BF00690158 |journal=Archives of Microbiology |language=en |volume=146 |issue=1 |pages=52–56 |doi=10.1007/BF00690158 |issn=1432-072X}}</ref> and the end product is sulfate. The sulfur, which is deposited extracellularly, is in the form of sulfur globules, which can be later oxidized completely.<ref name=":1" />
+Green sulfur bacteria oxidize inorganic sulfur compounds to use as electron donors for anaerobic photosynthesis, specifically in carbon dioxide fixation. They usually prefer to utilize sulfide over other sulfur compounds as an electron donor, however they can utilize thiosulfate or H<sub>2</sub>.<ref name=":1">{{Citation |last1=Frigaard |first1=Niels-Ulrik |title=Sulfur Metabolism in Phototrophic Sulfur Bacteria |date=2008-01-01 |url=https://www.sciencedirect.com/science/article/pii/S0065291108000027 |work=Advances in Microbial Physiology |volume=54 |pages=103–200 |editor-last=Poole |editor-first=Robert K. |publisher=Academic Press |language=en |access-date=2022-04-22 |last2=Dahl |first2=Christiane}}</ref> The intermediate is usually sulfur, which is deposited outside of the cell,<ref>{{Cite journal |last=van Gemerden |first=Hans |date=1986-10-01 |title=Production of elemental sulfur by green and purple sulfur bacteria |url=https://doi.org/10.1007/BF00690158 |journal=Archives of Microbiology |language=en |volume=146 |issue=1 |pages=52–56 |doi=10.1007/BF00690158 |s2cid=30812886 |issn=1432-072X}}</ref> and the end product is sulfate. The sulfur, which is deposited extracellularly, is in the form of sulfur globules, which can be later oxidized completely.<ref name=":1" />
-The mechanisms of sulfur oxidation in green sulfur bacteria are not well characterized. Some enzymes thought to be involved in sulfide oxidation include flavocytochrome c, sulfide:quinone oxidoreductase and the Sox system. Flavocytochrome can catalyze the transfer of electrons to cytochromes from sulfide, and these cytochromes could then move the electrons to the photosynthetic reaction center. However, not all green sulfur bacteria produce this enzyme, demonstrating that it is not needed for the oxidation of sulfide. Sulfide:quinone oxidoreductase (SQR) also helps with electron transport, but, when alone, has been found to produce decreased rates of sulfide oxidation in green sulfur bacteria, suggesting that there is a different, more effective mechanism.<ref name=":1" /> However, most green sulfur bacteria contain a homolog of the SQR gene.<ref name=":2">{{Cite journal |last=Gregersen |first=Lea |last2=Bryant |first2=Donald |last3=Frigaard |first3=Niels-Ulrik |date=2011 |title=Mechanisms and Evolution of Oxidative Sulfur Metabolism in Green Sulfur Bacteria |url=https://www.frontiersin.org/article/10.3389/fmicb.2011.00116 |journal=Frontiers in Microbiology |volume=2 |doi=10.3389/fmicb.2011.00116/full#:~:text=green%20sulfur%20bacteria%20(gsb;%20order,where%20light%20and%20sulfide%20coincide |issn=1664-302X}}</ref> The oxidation of thiosulfate to sulfate could be catalyzed by the enzymes in the Sox system.<ref name=":1" />
+The mechanisms of sulfur oxidation in green sulfur bacteria are not well characterized. Some enzymes thought to be involved in sulfide oxidation include flavocytochrome c, sulfide:quinone oxidoreductase and the Sox system. Flavocytochrome can catalyze the transfer of electrons to cytochromes from sulfide, and these cytochromes could then move the electrons to the photosynthetic reaction center. However, not all green sulfur bacteria produce this enzyme, demonstrating that it is not needed for the oxidation of sulfide. Sulfide:quinone oxidoreductase (SQR) also helps with electron transport, but, when alone, has been found to produce decreased rates of sulfide oxidation in green sulfur bacteria, suggesting that there is a different, more effective mechanism.<ref name=":1" /> However, most green sulfur bacteria contain a homolog of the SQR gene.<ref name=":2">{{Cite journal |last1=Gregersen |first1=Lea |last2=Bryant |first2=Donald |last3=Frigaard |first3=Niels-Ulrik |date=2011 |title=Mechanisms and Evolution of Oxidative Sulfur Metabolism in Green Sulfur Bacteria |journal=Frontiers in Microbiology |volume=2 |page=116 |doi=10.3389/fmicb.2011.00116 |pmid=21833341 |pmc=3153061 |issn=1664-302X|doi-access=free }}</ref> The oxidation of thiosulfate to sulfate could be catalyzed by the enzymes in the Sox system.<ref name=":1" />
 It is thought that the enzymes and genes related to sulfur metabolism were obtained via [[horizontal gene transfer]] during the evolution of green sulfur bacteria.<ref name=":2" />