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原生生物的发现在1865年被科学界所认可，但是由于它们难以在实验室中培养，故研究人员仍不能够对其基因组成窥探一二。目前对原生生物的归类仅限于对其形态及大小的观察。1 w J3 G# h) Q2 `" L0 Y4 S1 y
近日，研究人员在挪威首都奥斯陆附近一湖中发现“人类的最远亲”—— 一种单细胞有机物，这类生物将被归到生命进化树(wiki)上一个全新的分支。! M6 Q1 s) x4 w- |% E$ b5 g. J
研究报告发表在3月21号的期刊《分子生物学与进化》(Molecular Biology Evolution)上，研究人员已经能够培养足够的称之为 Collodictyon 的原生生物(一种单细胞的真核细胞，地球上最古老的生物之一)，并在实验室分析它的基因组。研究人员发现该有机物从遗传学角度来说并不属于之前发现的任何一界(目前共分为原生生物界、真菌界、植物界和动物界)。
- c0 u9 u8 t e+ x, N% B 这种具有包膜内构的有机物被叫做真核细胞，从基因方面来说它并不属于动物、植物、真菌、藻类、原生生物这五类最基本的生物群组中的任何一种。该有机物是人类目前已知的的真核细胞有机体中最古老的一种。 它形成于10亿年以前(误差大概不超过两三亿年)。研究员Shalchian-Tabrizi指出：它让人类对于地球早期生命形态有了更好的认识。
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; G t- j! T/ Y1 n& y" q7 |' y! _ Collodictyon 的特征：体长只有30到50 微米(相当于人类发丝的宽度)。以藻类为食，不喜群居。拥有四根鞭毛(运动器官)而不是类似于其他同类生物只有一到两根鞭毛。
" B3 e: G: T8 C9 W4 u9 S之所以称其为奇葩是因为该生物的一些罕见特征同时与两种不同的真核界生物有着联系，原核生物和变形虫。4 A+ P; W. Y# {! k
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奥斯陆大学的研究员 Dag Klaveness 称：在经过与世界各地上百个基因数据库的基因数据比较后，只有一小部分的基因组与之前在西藏发现的生物基因序列相匹配。0 `1 z3 l4 o3 ~, V, @
研究人员认为该有机物应属于生命演化树的一个全新分支，虽然他们不能确定在遗传信息匮乏的情况下是否能将其归类于之前被归类为原生生物的有机物的相同的组别。因为它同两种截然不同的生物具有相同的特征。研究人员认为这种生物的祖先可能是这几种生物的共同祖先，包括变形虫和原生生物。如果假设成立，这将被视为人类已知的最古老的真核生物，是所有其他真核生物，包括人类的祖先。[via LiveScience] + S# y3 d5 K6 }, Q. R$ q N
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# B6 }; K( {, F) _/ ?科学家在名为阿斯(As)的小湖污泥中发现Collodictyon. 阿斯湖位于奥斯陆以南30公里。
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【来源】http://jandan.net/2012/04/30/collodictyon.html; {. k% m( ^/ |4 h+ ?1 j/ W
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Molecular Biology and Evolutionmbe.oxfordjournals.org - Mol Biol Evol (2012) doi: 10.1093/molbev/mss001 First published online: January 6, 2012 - T V3 f- B( S/ \
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Collodictyon – an ancient lineage in the tree of eukaryotes + Author Affiliations - 1Microbial Evolution Research Group (MERG), Department of Biology, University of Oslo, Oslo, Norway
- 2Canadian Institute for Advanced Research, Botany Department, University of British Columbia, Vancouver, British Columbia, Canada ' Y$ ]3 Q0 u4 W2 a" Y/ H& |, c
- ↵*Corresponding author Kamran Shalchian-Tabrizi Phone: +47 41045328 E-mail: Kamran@bio.uio.no- S: A( }/ K5 O9 P: x2 x
- Received March 3, 2011.
- Revision received June 3, 2011.
- Revision received August 27, 2011.
- Revision received November 25, 2011.
- Accepted December 16, 2011.
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AbstractThe current consensus for the eukaryote tree of life consists of several large assemblages (supergroups) that are hypothesized to describe the existing diversity. Phylogenomic analyses have shed light on the evolutionary relationships within and between supergroups as well as placed newly sequenced enigmatic species close to known lineages. Yet, a few eukaryote species remain of unknown origin and could represent key evolutionary forms for inferring ancient genomic and cellular characteristics of eukaryotes. Here, we investigate the evolutionary origin of the poorly studied protist Collodictyon (subphylum Diphylatia), by sequencing a cDNA library as well as the 18S and 28S rDNA genes. Phylogenomic trees inferred from 124 genes placed Collodictyon close to the bifurcation of the ‘unikont’ and ‘bikont’ groups, either alone or as sister to the potentially contentious excavate Malawimonas. Phylogenies based on rDNA genes confirmed that Collodictyon is closely related to another genus, Diphylleia, and revealed a very low diversity in environmental DNA samples. The early and distinct origin of Collodictyon suggests that it constitutes a new lineage in the global eukaryote phylogeny. Collodictyon shares cellular characteristics with Excavata and Amoebozoa, such as ventral feeding groove supported by microtubular structures and the ability to form thin and broad pseudopods. These may therefore be ancient morphological features among eukaryotes. Overall, this shows that Collodictyon is a key lineage to understand early eukaryote evolution.
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http://mbe.oxfordjournals.org/content/early/2012/01/06/molbev.mss001.short?rss=1. R6 M* v( R3 K! w7 m
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% d- [4 o7 u: j# |8 y( i" ^! l9 G科学家发现一种单细胞生物为人类已知最远亲* T" e) Q3 H7 L* j8 u( M
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http://www.sina.com.cn 2012年04月30日 08:21 南方都市报微博
1 s& R( Q+ @& i1 E. k$ H 据新华社电 挪威奥斯陆大学研究人员借助显微镜观察挪威湖泊中一种单细胞生物体20多年后宣布，这是地球上最古老的生物体之一，是已知的人类最远亲戚。
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0 Z* p$ k5 @6 D/ j; B" X 美国探索新闻网站28日援引研究人员的话报道，这种单细胞生物大约形成于10亿年前，以捕食藻类为生，不易发现。研究人员说，这种生物不属于任何一种已知生物体，也就是说，它不是动物，不是植物，不是寄生虫，不是真菌，也不是藻类。研究人员创出Collodictyon一词，用以命名这种生物体。( F$ t3 |5 t; w; F% a2 }+ L
* {# [/ s, _& |4 Q- T5 J6 { 奥斯陆大学沙尔希安-大不里士博士说：“我们发现了生命树上不为人知的一个分支，生活在湖泊中。它独一无二。我们还没有发现一种比它们更接近生命树根部的物种。”9 f1 X q! K0 a6 I" T/ f% o" N$ I
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研究人员认为，这一发现可能有助人们了解数亿年前地球上的生物样貌。这种生物体生活在奥斯陆以南30公里的阿斯湖淤泥中，有4条尾巴状的鞭毛，有助移动，体长30微米至50微米，必须借助显微镜才能看到。(来源：南方都市报）http://tech.sina.com.cn/d/2012-04-30/08217040869.shtml
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& |2 t0 f' Y# v& K5 k! NCollodictyon From Wikipedia, the free encyclopedia
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Jump to: navigation, search
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| This article needs attention from an expert on the subject. The specific problem is: The article has a mixture of statements of highly various reliability, sourced from (at the better end) reasonable scientific papers, but also (at the worse end) from near-nonsensical journalistic hype -- which sometimes actually contradicts the scientifically sourced material. It needs a real cleanup. WikiProject Biology or the Biology Portal may be able to help recruit an expert. (April 2012) |
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Collodictyon is a single-celled microscopic creature." ^1 j! N7 I; f
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5 R" y, r, v6 u6 ?; \8 XDiagram of "Collodictyon meeting Pandorina" sketched by researcher Robert Clinton Rhodes; sketch appeared in print in 1917.
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Sketch of Collodictyon looking from the rear, with four flagella.
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. A" Y `- Y4 GCollodictyon is a single-celled eukaryote[2] which is notable for being "one of the world's oldest living organisms".[3] In terms of evolution, Collodictyon may be "man's remotest relative", according to several reports.[3] In terms of taxonomy, the creature does not fall into any other known category of eukaryotes. Scientists speculate that further study of Collodictyon may yield insights into the prehistoric beginnings of life hundreds of millions of years ago.[2][4] Scientists from Norway have been studying a particular type of Collodictyon found living in sludge in Årungen, a lake in the municipality of Ås in Norway.[2][5] Kamran Shalchian-Tabrizi, the leader of the Microbial Evolution Research Group (MERG), claimed that these organisms resemble the basal eukaryote.[6] They range from 30 to 50 microns in length,[2] can grow broad pseudopodia, and have four flagella for motility[2] and a ventral feeding groove.[4]. Unlike bacteria, the creatures have cell nuclei which are enclosed by membranes.[2] Researcher Dag Klaveness reported that the creatures are "not sociable" and cannibalize each other when food is scarce.[2] Their closest relatives come from the Protist group Diphylleia.[7] Collodictyon triciliatum has four flagella connected to basal bodies, generally of equal length, as long as or slightly longer than the body of Collodictyon.[8] Number one flagellum is connected to a dorsal root, while number two flagellum is connected to a ventral root. Number three and four flagella are on either side of these two and have dorsal roots. The mitochondria have tubular cristae. Organelles called dictyosomes are arranged in a horseshoe.[9] Brugerolle proposed a family, Collodictyonidae for this genus and Diphylleia rotans.[9] Collodictyon triciliatum was originally named by H. J. Carter in 1865.[10] Originally found on the island of Bombay and later in central Europe,[11] this species is also found in Barcelona and Tarragona.[12] Another species C. sparsevacuolatum, named by Skuja is still recognised. It is found in freshwater in the United States and Europe. There is also a doubtful Collodictyon sphaericum described by R.E.Norris.[13] Carter's original species description is as follows: Pyriform, straight, or slightly bent upon itself, bifid at the small extremity, presenting at the larger one an indentation, from which spring three cilia. Structure transparent, cancellated, composed of globular cells, with a strongly marked, greenish granule here and there in the triangular spaces between them. Locomotive, swimming by means of the cilia; subpolymorphic, flexible, yielding, capable of assuming a globular form ... or one more or less modified by the body it may incept . . . ; enclosing crude material for nourishment in stomachal spaces, and ejecting the refuse, like Amoeba. Provided with a nucleus and contracting vesicles.
5 N+ V" ?) L+ L+ ^* O—Carter, 1865[11]6 ]7 \+ ~8 ~* @5 Q" P
Later researchers examined issues such as its feeding habits: In its feeding habits, Collodictyon is most interesting. When hungry, it can be distinguished from moribund stages in which all food is extruded by pseudopial projections from the lateral groove or sulcal region ... these pseudopodia ... function actively whenever the organism is seeking food. At these times when coming in contact with Protozoa or algae which it may use for food, they are wafted to the sulcal region by the flagella, or else Collodictyon aligns itself alongside of its prey with the pseudopodia in contact. ... Both the flagella and the pseudopodia appear sensitive to food stimulus ..." A; a8 g0 a4 O3 m, c7 H- w6 ?" \
—Robert Clinton Rhodes, 1919[14]
- j+ z6 W5 r! \, U! P) j2 G In 1917, it was classified as being one of the "simplest and most primitive" type of polymastigina.[15] [edit] References- ^ "Collodictyon – an ancient lineage in the tree of eukaryotes." Zhao, Sen et al. December 16, 2011. http://mbe.oxfordjournals.org/content/early/2012/01/06/molbev.mss001.short
- ^ a b c d e f g Agence France-Presse (AFP) (26 April 2012). "Scientists find 'man's remotest relative' in lake sludge". France 24 International News. http://www.france24.com/en/20120426-scientists-find-mans-remotest-relative-lake-sludge. Retrieved 2012-04-25.
$ r# W/ i9 \! F2 {9 {- @1 l - ^ a b Agence France-Presse (April 27, 2012). "Earliest human ancestor found". The Windsor Star. http://www2.canada.com/windsorstar/news/story.html?id=b8e8cc46-2d46-4804-a139-6e42a368bda6. Retrieved 2012-04-25. "...After two decades of examining a microscopic algae-eater that lives in a lake in Norway, scientists on Thursday declared it to be one of the world's oldest living organisms and man's remotest relative...."
" f! U$ Z# p) ~ w4 I) |' R# d% A, {& S4 b% p - ^ a b Zhao S, Burki F, Bråte J, Keeling PJ, Klaveness D, Shalchian-Tabrizi K. (2012 Mar 21). "Collodictyon--An Ancient Lineage in the Tree of Eukaryotes". Molecular Biology Evolution. http://www.ncbi.nlm.nih.gov/pubmed/22319147. Retrieved 2012-04-25. "Abstract: .... The early and distinct origin of Collodictyon suggests that it constitutes a new lineage in the global eukaryote phylogeny. Collodictyon shares cellular characteristics with Excavata and Amoebozoa, such as ventral feeding groove supported by microtubular structures and the ability to form thin and broad pseudopods. These may therefore be ancient morphological features among eukaryotes. Overall, this shows that Collodictyon is a key lineage to understand early eukaryote evolution.": D6 h: d/ L0 A/ l3 X
- ^ Yngve Vogt (23 April 2012). "Mankind's remotest relative". Apollon. http://www.apollon.uio.no/english/articles/2012/microorganism.html.
# M* n/ w0 o7 R- U Original Norwegian press release with pictures of researchers. - ^ "Scientists find 'man's remotest relative' in lake sludge". 26 April 2012. http://phys.org/news/2012-04-scientists-remotest-relative-lake-sludge.html.
5 M3 H0 g* R8 V3 ]. j+ g - ^ Zhao, Sen; Burki, Fabien; Bråte, Jon; Keeling, Patrick J.; Klaveness, Dag; Shalchian-Tabrizi, Kamran (2012). "Collodictyon—An Ancient Lineage in the Tree of Eukaryotes". Molecular Biology and Evolution. doi:10.1093/molbev/mss001.
! m8 U! a# t- w2 }+ d1 J3 F - ^ Rhodes, Robert Clinton (29 October 1917). Binary Fission in Collodictyon tricilliatum. Berkeley, California: University of Californa. http://ia700200.us.archive.org/21/items/binaryfissioninc00rhodrich/binaryfissioninc00rhodrich.pdf. "number of flagella is four (page 238 of original book; page 50 of the pdf file). Flagella equal in length, as long as the body or possibly longer..."$ W3 A6 t: l5 |5 W
- ^ a b Brugerolle, Guy; Bricheux G, Philippe H, Coffea G. (March 2002). "Collodictyon triciliatum and Diphylleia rotans (=Aulacomonas submarina) form a new family of flagellates (Collodictyonidae) with tubular mitochondrial cristae that is phylogenetically distant from other flagellate groups". Protist 153 (1): 59–70. PMID 12022276.7 \% q+ V7 I4 J |0 F
- ^ "On the fresh- and salt-water Rhizopoda of England and India.". Annals and Magazine of Natural History 3 (15): 277–293.3 r/ |* h- i" m- T
- ^ a b Rhodes, Robert Clinton (29 October 1917). Binary Fission in Collodictyon tricilliatum. Berkeley, California: University of Californa. http://ia700200.us.archive.org/21/items/binaryfissioninc00rhodrich/binaryfissioninc00rhodrich.pdf.. M; S1 i0 ^) |% ]& W* j$ _ l- H6 K, }
- ^ Cambra Sánchez, J.; Álvarez Cobelas, M. & Aboal Sanjurjo, M (1988). "Lista florística y bibliográfica de los clorófitos (Chlorophyta) de la Península Ibérica, Islas Baleares e Islas Canarias". Asociación Española de Limnología. p. 9. http://www.algaebase.org/pdf/5628C2061d8b133993QgU3570F03/catalogocloros.pdf. Retrieved 28 April 2012.4 Z8 F$ O' s5 h' J8 @6 m
- ^ M.D. Guiry in Guiry, M.D. & Guiry, G.M. 2012.. "Collodictyon H.J.Carter, 1865: 289". AlgaeBase. World-wide electronic publication. Galway: National University of Ireland. http://www.algaebase.org/search/genus/detail/?genus_id=45305. Retrieved 28 April 2012.+ Y* \0 X. Y6 V
- ^ Rhodes, Robert Clinton (29 October 1917). Binary Fission in Collodictyon tricilliatum. Berkeley, California: University of Californa. http://ia700200.us.archive.org/21/items/binaryfissioninc00rhodrich/binaryfissioninc00rhodrich.pdf. "(page 220 from original book; page 32 from the pdf) ... In its feeding habits, Collodictyon is most interesting. When hungry, it can be distinguished from moribund stages in which all food is extruded by pseudopial projections from the lateral groove or sulcal region ... these pseudopodia ... function actively whenever the organism is seeking food. At these times when coming in contact with Protozoa or algae which it may use for food, they are wafted to the sulcal region by the flagella, or else Collodictyon aligns itself alongside of its prey with the pseudopodia in contact. ... Both the flagella and the pseudopodia appear sensitive to food stimulus ..."
! i* b5 Y( G: h* o' J1 p - ^ Rhodes, Robert Clinton (29 October 1917). Binary Fission in Collodictyon tricilliatum. Berkeley, California: University of Californa. http://ia700200.us.archive.org/21/items/binaryfissioninc00rhodrich/binaryfissioninc00rhodrich.pdf. "(page 239 of original book; page 51 of pdf file) ... Collodictyon is "one of the simplest and most primitive of the Polymastigina"..."
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5 V/ I$ d% g4 d+ Mhttp://en.wikipedia.org/wiki/Collodictyon
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发表于 2012-4-30 21:57
发表于 2012-5-1 01:34
太神奇啦，，，教科书又要改版啦，，赶紧收录最新动态
