Biology:Pelagibacterales
| "Pelagibacterales" | |
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| Microscopy image of SAR11 | |
| Scientific classification | |
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| Subclass: | Rickettsidae
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| Order: | "Pelagibacterales" Grote et al. 2012[1]
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The Pelagibacterales are an order in the Alphaproteobacteria composed of free-living marine bacteria that make up roughly one in three cells at the ocean's surface.[2][3][4] Overall, members of the Pelagibacterales are estimated to make up between a quarter and a half of all prokaryotic cells in the ocean.[5]
Initially, this taxon was known solely by metagenomic data and was known as the SAR11 clade. It was first placed in the Rickettsiales, but was later raised to the rank of order, and then placed as sister order to the Rickettsiales in the subclass Rickettsidae.[4] It includes the highly abundant marine species Pelagibacter ubique.
Bacteria in this order are unusually small.[6] Due to their small genome size and limited metabolic function, Pelagibacterales have become a model organism for 'streamlining theory'.[5]
P. ubique and related species are oligotrophs (scavengers) and feed on dissolved organic carbon and nitrogen.[3] They are unable to fix carbon or nitrogen, but can perform the TCA cycle with glyoxylate bypass and are able to synthesise all amino acids except glycine,[7] as well as some cofactors.[8] They also have an unusual and unexpected requirement for reduced sulfur.[9]
P. ubique and members of the oceanic subgroup I possess gluconeogenesis, but not a typical glycolysis pathway, whereas other subgroups are capable of typical glycolysis.[10]
Unlike Acaryochloris marina, P. ubique is not photosynthetic — specifically, it does not use light to increase the bond energy of an electron pair — but it does possess proteorhodopsin (including retinol biosynthesis) for ATP production from light.[11]
SAR11 bacteria are responsible for much of the dissolved methane in the ocean surface. They extract phosphate from methylphosphonic acid.[12]
Although the taxon derives its name from the type species P. ubique (status Candidatus species), this species has not yet been validly published, and therefore neither the order name nor the species name has official taxonomic standing.[13]
Subgroups
Currently, the order is divided into five subgroups:[14]
- Subgroup Ia, open ocean, crown group — includes P. ubique HTCC1062
- Subgroup Ib, open ocean, sister clade to Ia
- Subgroup II, coastal, basal to Ia + Ib
- Subgroup III, brackish, basal to I + II along with its sister clade IV
- Subgroup IV, also known as the LD12 clade, freshwater[15]
- Subgroup V, which includes alphaproteobacterium HIMB59, basal to the remainder
The above results in a cladogram of the Pelagibacterales as follows:
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Subgroup V (includes α-proteobacterium HIMB59) | |||||||||||||||||||||||||||||||
Phylogenetic placement and endosymbiotic theory
A 2011 study by researchers of the University of Hawaiʻi at Mānoa and Oregon State University, indicated that SAR11 could be the ancestor of mitochondria in most eukaryotic cells.[2] However, this result could represent a tree reconstruction artifact due to compositional bias.[16]
| Schematic ribosomal RNA phylogeny of Alphaproteobacteria | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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| The cladogram of Rickettsidae has been inferred by Ferla et al. [4] from the comparison of 16S + 23S ribosomal RNA sequences. |
References
- ↑ 1.0 1.1 "Streamlining and core genome conservation among highly divergent members of the SAR11 clade.". mBio 3 (5): 1–13. 2012. doi:10.1128/mBio.00252-12. PMID 22991429.
- ↑ 2.0 2.1 J. Cameron Thrash; Alex Boyd; Megan J. Huggett; Jana Grote; Paul Carini; Ryan J. Yoder; Barbara Robbertse; Joseph W. Spatafora et al. (June 2011). "Phylogenomic evidence for a common ancestor of mitochondria and the SAR11 clade". Scientific Reports 1: 13. doi:10.1038/srep00013. PMID 22355532. Bibcode: 2011NatSR...1E..13T.
- ↑ 3.0 3.1 "SAR11 clade dominates ocean surface bacterioplankton communities". Nature 420 (6917): 806–10. 2002. doi:10.1038/nature01240. PMID 12490947. Bibcode: 2002Natur.420..806M.
- ↑ 4.0 4.1 4.2 "New rRNA gene-based phylogenies of the Alphaproteobacteria provide perspective on major groups, mitochondrial ancestry and phylogenetic instability". PLOS One 8 (12): e83383. 2013. doi:10.1371/journal.pone.0083383. PMID 24349502.
- ↑ 5.0 5.1 Giovannoni, Stephen J. (2017-01-03). "SAR11 Bacteria: The Most Abundant Plankton in the Oceans". Annual Review of Marine Science 9: 231–255. doi:10.1146/annurev-marine-010814-015934. ISSN 1941-0611. PMID 27687974. Bibcode: 2017ARMS....9..231G.
- ↑ "Cultivation of the ubiquitous SAR11 marine bacterioplankton clade". Nature 418 (6898): 630–3. August 2002. doi:10.1038/nature00917. PMID 12167859. Bibcode: 2002Natur.418..630R.
- ↑ H. James Tripp; Michael S. Schwalbach; Michelle M. Meyer; Joshua B. Kitner; Ronald R. Breaker; Stephen J. Giovannoni (January 2009). "Unique glycine-activated riboswitch linked to glycine-serine auxotrophy in SAR11". Environmental Microbiology 11 (1): 230–8. doi:10.1111/j.1462-2920.2008.01758.x. PMID 19125817.
- ↑ Giovannoni, S. J.; Tripp, H. J.; Givan, S.; Podar, M.; Vergin, K. L.; Baptista, D.; Bibbs, L.; Eads, J. et al. (2005). "Genome Streamlining in a Cosmopolitan Oceanic Bacterium". Science 309 (5738): 1242–1245. doi:10.1126/science.1114057. PMID 16109880. Bibcode: 2005Sci...309.1242G.
- ↑ H. James Tripp; Joshua B. Kitner; Michael S. Schwalbach; John W. H. Dacey; Larry J. Wilhelm; Stephen J. Giovannoni (April 2008). "SAR11 marine bacteria require exogenous reduced sulfur for growth". Nature 452 (7188): 741–4. doi:10.1038/nature06776. PMID 18337719. Bibcode: 2008Natur.452..741T.
- ↑ Schwalbach, M. S.; Tripp, H. J.; Steindler, L.; Smith, D. P.; Giovannoni, S. J. (2010). "The presence of the glycolysis operon in SAR11 genomes is positively correlated with ocean productivity". Environmental Microbiology 12 (2): 490–500. doi:10.1111/j.1462-2920.2009.02092.x. PMID 19889000.
- ↑ Giovannoni, S. J.; Bibbs, L.; Cho, J. C.; Stapels, M. D.; Desiderio, R.; Vergin, K. L.; Rappé, M. S.; Laney, S. et al. (2005). "Proteorhodopsin in the ubiquitous marine bacterium SAR11". Nature 438 (7064): 82–85. doi:10.1038/nature04032. PMID 16267553. Bibcode: 2005Natur.438...82G.
- ↑ Carini, P.; White, A. E.; Campbell, E. O.; Giovannoni, S. J. (2014). "Methane production by phosphate-starved SAR11 chemoheterotrophic marine bacteria". Nature Communications 5: 4346. doi:10.1038/ncomms5346. PMID 25000228. Bibcode: 2014NatCo...5.4346C.
- ↑ Don J. Brenner; Noel R. Krieg; James T. Staley (July 26, 2005). George M. Garrity. ed. The Proteobacteria. Bergey's Manual of Systematic Bacteriology. 2C (2nd ed.). New York: Springer. pp. 1388. British Library no. GBA561951. ISBN 978-0-387-24145-6. https://archive.org/details/bergeysmanualofs00boon/page/1388.
- ↑ Robert M. Morris, K.L.V., Jang-Cheon Cho, Michael S. Rappé, Craig A. Carlson, Stephen J. Giovannoni, Temporal and Spatial Response of Bacterioplankton Lineages to Annual Convective Overturn at the Bermuda Atlantic Time-Series Study Site" Limnology and Oceanography 50(5) p. 1687-1696.
- ↑ Salcher, M.M., J. Pernthaler, and T. Posch, Seasonal bloom dynamics and ecophysiology of the freshwater sister clade of SAR11 bacteria 'that rule the waves' (LD12). ISME J, 2011.
- ↑ "The SAR11 group of alpha-proteobacteria is not related to the origin of mitochondria". PLOS ONE 7 (1): e30520. 2012. doi:10.1371/journal.pone.0030520. PMID 22291975. Bibcode: 2012PLoSO...730520R.
Wikidata ☰ Q7388740 entry
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