Prochlorococcus

Taxobox
name = "Prochlorococcus"

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image_width = 200px
image_caption =
regnum = Bacteria
divisio = Cyanobacteria
ordo = Synechococcales
familia = Synechococcaceae
genus = "Prochlorococcus"
genus_authority = Chisholm et al., 1992
subdivision_ranks = Species
subdivision = "P. marinus"

"Prochlorococcus" is a genus of very small (0.6 µm) marine cyanobacteria with an unusual pigmentation (chlorophyll "b") belonging to photosynthetic picoplankton. It is probably the most abundant photosynthetic organism on Earth.

Overview

Although there had been several earlier records of very small chlorophyll-"b"-containing cyanobacteria in the ocean [cite journal |quotes=no |author=P. W. Johnson & J. M. Sieburth |year=1979 |title=Chroococcoid cyanobacteria in the sea: a ubiquitous and diverse phototrophic biomass |journal=Limnology and Oceanography |volume=24 |pages=928–935] [cite journal |quotes=no |author=W. W. C. Gieskes & G. W. Kraay |year=1983 |title=Unknown chlorophyll "a" derivatives in the North Sea and the tropical Atlantic Ocean revealed by HPLC analysis |journal=Limnology and Oceanography |volume=28 |pages=757–766] , "Prochlorococcus" was actually discovered in 1986 [cite journal |quotes=no |author=S. W. Chisholm, R. J. Olson, E. R. Zettler, J. Waterbury, R. Goericke & N. Welschmeyer |year=1988 |title=A novel free-living prochlorophyte occurs at high cell concentrations in the oceanic euphotic zone |journal=Nature |volume=334 |pages=340–343 |doi=10.1038/334340a0] by Sallie W. (Penny) Chisholm of the Massachusetts Institute of Technology, Robert J. Olson of the Woods Hole Oceanographic Institution, and other collaborators in the Sargasso Sea using flow cytometry. The first culture of "Prochlorococcus" was isolated in the Sargasso Sea in 1988 (strain SS120) and shortly another strain was obtained from the Mediterranean Sea (strain MED). The name "Prochlorococcus" [cite journal |quotes=no |author=Sallie W. Chisholm, S. L. Frankel, R. Goericke, R. J. Olson, B. Palenik, J. B. Waterbury, L. West-Johnsrud & E. R. Zettler |year=1992 |title="Prochlorococcus marinus" nov. gen. nov. sp.: an oxyphototrophic marine prokaryote containing divinyl chlorophyll a and b |journal=Archives of Microbiology |volume=157 |pages=297–300 |doi=10.1007/BF00245165] originated from the fact it was originally assumed that "Prochlorococcus" was related to "Prochloron" and other chlorophyll "b" containing bacteria, called prochlorophytes, but it is now known that prochlorophytes form several separate phylogenetic groups within the cyanobacteria subgroup of the bacteria kingdom.

Marine cyanobacteria are to date the smallest known photosynthetic organisms: "Prochlorococcus" is the smallest at just 0.5 to 0.8 micrometres across. Possibly they are also the most plentiful species on Earth: a single millilitre of surface seawater may contain 100,000 cells or more. Worldwide, there are estimated to be 100 octillion (10²⁹) individuals. [cite web |url=http://antwrp.gsfc.nasa.gov/apod/ap060927.html |title=DGF |publisher=NASA] "Prochlorococcus" is ubiquitous between 40°N and 40°S and dominates in the oligotrophic (nutrient poor) regions of the oceans [cite journal |quotes=no |author=F. Partensky, W. R. Hess & D. Vaulot |year=1999 |title="Prochlorococcus", a marine photosynthetic prokaryote of global significance |journal=Microbiology and Molecular Biology Reviews |volume=63 |pages=106–127] . The bacterium accounts for an estimated 20% of the oxygen in the earth's atmosphere, and forms part of the base of the ocean food chain. [http://www.npr.org/templates/story/story.php?storyId=91448837 The Most Important Microbe You've Never Heard Of] ]

The light harvesting pigment complement of "Prochlorococcus" is unique, consisting predominantly of divinyl derivatives of chlorophyll a (Chl a2) and b (Chl b2) and lacking monovinyl chlorophylls. "Prochlorococcus" occupies two distinct niches, leading to the nomenclature of the low light (LL) and high light (HL) groups [cite journal |quotes=no |author=N. J. West & D. J. Scanlan |year=1999 |title=Niche-partitioning of "Prochlorococcus" in a stratified water column in the eastern North Atlantic Ocean |journal=Applied and Environmental Microbiology |volume=65 |pages=2585–2591] , which vary in pigment ratios (LL possess a high ration of chlorophyll b2: a2 and HL low b2: a2), light requirements, nitrogen and phosphorus utilization, copper and virus sensitivity. These "ecotypes" can be differentiated on the basis of the sequence of their ribosomal RNA gene. Recently the genomes of several strains of "Prochlorococcus" have been sequenced [cite journal |quotes=no |author=G. Rocap, F. W. Larimer, J. Lamerdin, S. Malfatti, P. Chain, N. A. Ahlgren, A. Arellano, M. Coleman, L. Hauser, W. R. Hess, Z. I. Johnson, M. Land, D. Lindell, A. F. Post, W. Regala, M. Shah, S. L. Shaw, C. Steglich, M. B. Sullivan, C. S. Ting, A. Tolonen, E. A. Webb, E. R. Zinser & S. W. Chisholm |year=2003 |title=Genome divergence in two "Prochlorococcus" ecotypes reflects oceanic niche differentiation |journal=Nature |volume=424 |pages=1042–1047 |url=http://web.mit.edu/mbsulli/www/Rocap-etal-2003.pdf |doi=10.1038/nature01947] [cite journal |quotes=no |author=A. Dufresne, M. Salanoubat, F. Partensky, F. Artiguenave, I. M. Axmann, V. Barbe, S. Duprat, M. Y. Galperin, E. V. Koonin, F. Le Gall, K. S. Makarova, M. Ostrowski, S. Oztas, C. Robert, I. B. Rogozin, D. J. Scanlan, N. Tandeau de Marsac, J. Weissenbach, P. Wincker, Y. I. Wolf & W. R. Hess |year=2003 |title=Genome sequence of the cyanobacterium "Prochlorococcus marinus" SS120, a nearly minimal oxyphototrophic genome |journal=Proceedings of the National Academy of Sciences |volume=100 |pages=10020–10025 |url=http://www.pnas.org/cgi/content/abstract/100/17/10020 |doi=10.1073/pnas.1733211100 |pmid=12917486] .

References

Further reading

*cite journal |quotes=no |author=L. Campbell, H. A. Nolla & D. Vaulot |year=1994 |title=The importance of "Prochlorococcus" to community structure in the central North Pacific Ocean |journal=Limnology and Oceanography |volume=39 |pages=954–961
*cite journal |quotes=no |author=Jagroop Pandhal, Phillip C. Wright & Catherine A. Biggs |year=2007 |title=A quantitative proteomic analysis of light adaptation in a globally significant marine cyanobacterium "Prochlorococcus marinus" MED4 |journal=Journal of Proteome Research |volume=6 |issue=3 |pages=996–1005 |id=doi|10.1021/pr060460c S1535-3893(06)00460-X |doi=10.1021/pr060460c
*cite journal |quotes=no |author=Steve Nadis |title=The cells that rule the seas: the ocean’s tiniest inhabitants, notes biological researcher Sallie W. Chisholm, hold the key to understanding the biosphere — and what happens when humans disrupt it |journal=Scientific American |year=2003 |pages=52f |url=http://sciam.com/article.cfm?chanID=sa022&articleID=0005BE47-0078-1FA8-807883414B7F0000

See also

* Photosynthetic picoplankton
* "Synechococcus"

External links

*cite web |url=http://www.algaebase.org/search/genus/detail/?genus_id=46076 |title="Prochlorococcus" S.W. Chisholm, S.L. Frankel, R. Goericke, R.J. Olson, B. Palenik, J.B. Waterbury, L. West-Johnsrud & E.R. Zettler 1992: 299 |author=M. D. Guiry |date= |work=AlgaeBase
* [http://www.npr.org/templates/story/story.php?storyId=91448837 The Most Important Microbe You've Never Heard Of] : NPR Story on "Prochlorococcus"