Tetrahymena

Taxobox | color = khaki
name = "Tetrahymena"

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image_size = 200px
image_caption = "Tetrahymena thermophila"
domain = Eukaryota
unranked_phylum = Alveolata
phylum = Ciliophora
classis = Oligohymenophorea
ordo = Hymenostomatida
familia = Tetrahymenidae
genus = "Tetrahymena"
subdivision_ranks = Species
subdivision = "T hegewischi" "T. hyperangularis" "T. malaccensis" "T. pigmentosa" "T. pyriformis" "T. thermophila" "T. vorax"

"Tetrahymena" are free-living ciliate protozoa that can also switch from commensalistic to pathogenic modes of survival. They are common in fresh-water. "Tetrahymena" species used as model organisms in biomedical research are "T. thermophila" and "T. pyriformis". [cite book | author=Alfred M. Elliott | title=Biology of Tetrahymena| journal=Dowen, Hutchinson and Ross Inc.| year=1973 | volume=ISBN 0-87933-013-9]

"T. thermophila": a model organism in experimental biology

As a ciliated protozoan, "Tetrahymena thermophila" exhibits striking nuclear dimorphism: two types of cell nuclei, a large, somatic macronucleus and a small, germline micronucleus, exist in a single cell at the same time and carry out different functions with distinct cytological and biochemical properties. This unique versatility allows scientists to use "Tetrahymena" to identify several key factors regarding gene expression and genome integrity. In addition, "Tetrahymena" possesses hundreds of cilia and has complicated microtubule structures, making it also an ideal model to elucidate the diversity and functions of microtubule systems .

Since "Tetrahymena" can be easily cultured in a large quantity in the laboratory, for years it has been a great source for biochemical analysis of important enzymatic activities and for purification of sub-cellular components. In addition, advanced molecular genetic techniques have been developed, including DNA-mediated transformation, gene 'knock-out' and 'knock-in' by homologous recombination, epitope tagging and inducible/repressible gene expression, making it an excellent model to study the gene function "in vivo". Recently, the whole macronuclear genome has been sequenced, which should promise "Tetrahymena" to be continuously utilized as a model system in the genomic and post-genomic era.Studies on "Tetrahymena" have contributed to several scientific milestones:
# First cell whose division was synchronized , leading to the first insights into the existence of cell cycle control mechanisms.
# Identification and purification of the first cytoskeleton motor protein, i.e., "dynein" and determination of its directional activity.
# Participation in the discovery of "lysosomes" and "peroxisomes".
# One of earliest molecular descriptions of somatic genome rearrangement.
# Discovery of the molecular structure of "telomeres" , "telomerase" enzyme , the templating role of telomerase RNA and their roles in cellular senescence and chromosome healing.
# Nobel-prize winning co-discovery of catalytic RNA ("ribozyme");
# Discovery of the function of histone acetylation.
# Discovery of the roles of RNA interference-like pathway in the heterochromatin formation
# Demonstration of the physiological roles of the posttranslational modification (i.e. acetylation and glycylation) on tubulins and identification of the enzymes responsible for some of the modifications (glutamylation).

(1 to 7 were adapted from [http://www.lifesci.ucsb.edu/~genome/Tetrahymena/SeqInitiative/WhitePaper.htm Tetrahymena Genome Sequencing White Paper] )

References

Further reading

1. "Methods in Cell Biology" Volume 62: "Tetrahymena thermophila", Edited by David J. Asai and James D. Forney. (2000). By Academic PressISBN 0-12-544164-9

2. Collins, K. and Gorovsky, M.A. (2005). Tetrahymena thermophila [http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VRT-4G4MGCB-4&_coverDate=05%2F10%2F2005&_alid=329058124&_rdoc=1&_fmt=&_orig=search&_qd=1&_cdi=6243&_sort=d&view=c&_acct=C000022660&_version=1&_urlVersion=0&_userid=483663&md5=765b7fa56bc464a104df3eb69725f828 "Curr Biol." 15: R317-8] .

3. [http://biology.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pbio.0040286 Eisen JA, Coyne RS, Wu M, Wu D, Thiagarajan M, et al. (2006) Macronuclear Genome Sequence of the Ciliate Tetrahymena thermophila, a Model Eukaryote. PLoS Biol 4(9): e286]

External links

* [http://www.ciliate.org "Tetrahymena" Genome Database]
* [http://www.tigr.org/tdb/e2k1/ttg/index.shtml "Tetrahymena thermophila" Genome Project] at The Institute for Genomic Research
* [http://biology.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pbio.0040304 "Tetrahymena thermophila" Genome Sequence Synopsis]
* [http://biology.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pbio.0040286 "Tetrahymena thermophila" genome paper]

Microbial Digital Specimen Archives: [http://mtlab.biol.tsukuba.ac.jp/WWW/PDB/Images/Ciliophora/Tetrahymena/ "Tetrahymena" image gallery]