The Crenarchaeota (also known as Crenarchaea or eocytes) are archaea that have been classified as a phylum of the Archaea domain.[1][2][3] Initially, the Crenarchaeota were thought to be sulfur-dependent extremophiles but recent studies have identified characteristic Crenarchaeota environmental rRNA indicating the organisms may be the most abundant archaea in the marine environment.[4] Originally, they were separated from the other archaea based on rRNA sequences; other physiological features, such as lack of histones, have supported this division, although some crenarchaea were found to have histones.[5] Until recently all cultured Crenarchaea had been thermophilic or hyperthermophilic organisms, some of which have the ability to grow at up to 113 °C.[6] These organisms stain Gram negative and are morphologically diverse, having rod, cocci, filamentous and oddly-shaped cells.[7]
One of the best characterized members of the Crenarcheota is Sulfolobus solfataricus. This organism was originally isolated from geothermally heated sulfuric springs in Italy, and grows at 80 °C and pH of 2–4.[8] Since its initial characterization by Wolfram Zillig, a pioneer in thermophile and archaean research, similar species in the same genus have been found around the world. Unlike the vast majority of cultured thermophiles, Sulfolobus grows aerobically and chemoorganotrophically (gaining its energy from organic sources such as sugars). These factors allow a much easier growth under laboratory conditions than anaerobic organisms and have led to Sulfolobus becoming a model organism for the study of hyperthermophiles and a large group of diverse viruses that replicate within them.
Marine species
Beginning in 1992, data were published that reported sequences of genes belonging to the Crenarchaea in marine environments.[9],[10] Since then, analysis of the abundant lipids from the membranes of Crenarchaea taken from the open ocean have been used to determine the concentration of these “low temperature Crenarchaea” (See TEX-86). Based on these measurements of their signature lipids, Crenarchaea are thought to be very abundant and one of the main contributors to the fixation of carbon .[citation needed] DNA sequences from Crenarchaea have also been found in soil and freshwater environments, suggesting that this phylum is ubiquitous to most environments.[11]
In 2005, evidence of the first cultured “low temperature Crenarchaea” was published. Named Nitrosopumilus maritimus, it is an ammonia-oxidizing organism isolated from a marine aquarium tank and grown at 28 °C.[12]
The eocyte hypothesis proposed in the 1980s by James Lake suggests that eukaryotes emerged within the prokaryotic eocytes.[14]
One possible piece of evidence supporting a close relationship between Crenarchaea and eukaryotes is the presence of a homolog of the RNA polymerase subunit Rbp-8 in Crenarchea but not in Euryarchaea[15]
↑"Pyrolobus fumarii, gen. and sp. nov., represents a novel group of archaea, extending the upper temperature limit for life to 113 °C". Extremophiles1 (1): 14–21. 1997. doi:10.1007/s007920050010. PMID9680332.
↑"The Sulfolobus-"Caldariellard" group: Taxonomy on the basis of the structure of DNA-dependent RNA polymerases". Arch. Microbiol.125 (3): 259–269. 1980. doi:10.1007/BF00446886.
↑Kwapisz, M; Beckouët, F; Thuriaux, P (2008). "Early evolution of eukaryotic DNA-dependent RNA polymerases". Trends Genet.24 (5): 211–5. doi:10.1016/j.tig.2008.02.002. PMID18384908.
Further reading
Scientific journals
Cavalier-Smith, T (2002). "The neomuran origin of archaebacteria, the negibacterial root of the universal tree and bacterial megaclassification". Int. J. Syst. Evol. Microbiol.52 (Pt 1): 7–76. doi:10.1099/00207713-52-1-7. PMID11837318.
Stackebrandt, E; Frederiksen W; Garrity GM; Grimont PA; Kampfer P; Maiden MC; Nesme X; Rossello-Mora R et al. (2002). "Report of the ad hoc committee for the re-evaluation of the species definition in bacteriology". Int. J. Syst. Evol. Microbiol.52 (Pt 3): 1043–1047. doi:10.1099/ijs.0.02360-0. PMID12054223.
Gurtler, V; Mayall BC (2001). "Genomic approaches to typing, taxonomy and evolution of bacterial isolates". Int. J. Syst. Evol. Microbiol.51 (Pt 1): 3–16. doi:10.1099/00207713-51-1-3. PMID11211268.
Dalevi, D; Hugenholtz P; Blackall LL (2001). "A multiple-outgroup approach to resolving division-level phylogenetic relationships using 16S rDNA data". Int. J. Syst. Evol. Microbiol.51 (Pt 2): 385–391. doi:10.1099/00207713-51-2-385. PMID11321083.
Keswani, J; Whitman WB (2001). "Relationship of 16S rRNA sequence similarity to DNA hybridization in prokaryotes". Int. J. Syst. Evol. Microbiol.51 (Pt 2): 667–678. doi:10.1099/00207713-51-2-667. PMID11321113.
Young, JM (2001). "Implications of alternative classifications and horizontal gene transfer for bacterial taxonomy". Int. J. Syst. Evol. Microbiol.51 (Pt 3): 945–953. doi:10.1099/00207713-51-3-945. PMID11411719.
Christensen, H; Bisgaard M; Frederiksen W; Mutters R; Kuhnert P; Olsen JE (2001). "Is characterization of a single isolate sufficient for valid publication of a new genus or species? Proposal to modify recommendation 30b of the Bacteriological Code (1990 Revision)". Int. J. Syst. Evol. Microbiol.51 (Pt 6): 2221–2225. doi:10.1099/00207713-51-6-2221. PMID11760965.
Christensen, H; Angen O; Mutters R; Olsen JE; Bisgaard M (2000). "DNA-DNA hybridization determined in micro-wells using covalent attachment of DNA". Int. J. Syst. Evol. Microbiol.50 (3): 1095–1102. doi:10.1099/00207713-50-3-1095. PMID10843050.
Xu, HX; Kawamura Y; Li N; Zhao L; Li TM; Li ZY; Shu S; Ezaki T (2000). "A rapid method for determining the G+C content of bacterial chromosomes by monitoring fluorescence intensity during DNA denaturation in a capillary tube". Int. J. Syst. Evol. Microbiol.50 (4): 1463–1469. doi:10.1099/00207713-50-4-1463. PMID10939651.
Young, JM (2000). "Suggestions for avoiding on-going confusion from the Bacteriological Code". Int. J. Syst. Evol. Microbiol.50 (4): 1687–1689. doi:10.1099/00207713-50-4-1687. PMID10939677.
Hansmann, S; Martin W (2000). "Phylogeny of 33 ribosomal and six other proteins encoded in an ancient gene cluster that is conserved across prokaryotic genomes: influence of excluding poorly alignable sites from analysis". Int. J. Syst. Evol. Microbiol.50 (4): 1655–1663. doi:10.1099/00207713-50-4-1655. PMID10939673.
Tindall, BJ (1999). "Proposal to change the Rule governing the designation of type strains deposited under culture collection numbers allocated for patent purposes". Int. J. Syst. Bacteriol.49 (3): 1317–1319. doi:10.1099/00207713-49-3-1317. PMID10490293.
Tindall, BJ (1999). "Proposal to change Rule 18a, Rule 18f and Rule 30 to limit the retroactive consequences of changes accepted by the ICSB". Int. J. Syst. Bacteriol.49 (3): 1321–1322. doi:10.1099/00207713-49-3-1321. PMID10425797.
Tindall, BJ (1999). "Proposals to update and make changes to the Bacteriological Code". Int. J. Syst. Bacteriol.49 (3): 1309–1312. doi:10.1099/00207713-49-3-1309. PMID10425795.
Burggraf, S; Huber H; Stetter KO (1997). "Reclassification of the crenarchael orders and families in accordance with 16S rRNA sequence data". Int. J. Syst. Bacteriol.47 (3): 657–660. doi:10.1099/00207713-47-3-657. PMID9226896.
Palys, T; Nakamura LK; Cohan FM (1997). "Discovery and classification of ecological diversity in the bacterial world: the role of DNA sequence data". Int. J. Syst. Bacteriol.47 (4): 1145–1156. doi:10.1099/00207713-47-4-1145. PMID9336922.
Euzeby, JP (1997). "List of Bacterial Names with Standing in Nomenclature: a folder available on the Internet". Int. J. Syst. Bacteriol.47 (2): 590–592. doi:10.1099/00207713-47-2-590. PMID9103655.
Clayton, RA; Sutton G; Hinkle PS Jr; Bult C; Fields C (1995). "Intraspecific variation in small-subunit rRNA sequences in GenBank: why single sequences may not adequately represent prokaryotic taxa". Int. J. Syst. Bacteriol.45 (3): 595–599. doi:10.1099/00207713-45-3-595. PMID8590690.
Murray, RG; Schleifer KH (1994). "Taxonomic notes: a proposal for recording the properties of putative taxa of procaryotes". Int. J. Syst. Bacteriol.44 (1): 174–176. doi:10.1099/00207713-44-1-174. PMID8123559.
Winker, S; Woese CR (1991). "A definition of the domains Archaea, Bacteria and Eucarya in terms of small subunit ribosomal RNA characteristics". Syst. Appl. Microbiol.14 (4): 305–310. doi:10.1016/s0723-2020(11)80303-6. PMID11540071.