color = #FFC8A0
name = "Entamoeba"
domain = Eukaryota
phylum = Amoebozoa
classis = Archamoebae
genus = "Entamoeba"
subdivision_ranks = Species
subdivision =

"E. coli"
"E. dispar"
"E. gingivalis"

"E. histolytica"

"E. invadens"
"E. moshkovskii"

"Entamoeba" is a genus of Amoebozoa found as internal parasites or commensals of animals. Several species are found in humans. "Entamoeba histolytica" is the pathogen responsible for "amoebiasis" (which includes amoebic dysentery and amoebic liver abscesses), while others such as "Entamoeba coli" and "E. dispar" are harmless. With the exception of "Entamoeba gingivalis", which lives in the mouth, and "E. moshkovskii", which is frequently isolated from river and lake sediments, all "Entamoeba" species are found in the intestines of the animals they infect.

"Entamoeba" cells are small, with a single nucleus and typically a single lobose pseudopod taking the form of a clear anterior bulge. They have a simple life cycle. The trophozoite (feeding-dividing form) is approximately 10-20 μm in diameter and feeds primarily on bacteria. It divides by simple binary fission to form two smaller daughter cells. Almost all species form cysts, the stage involved in transmission (the exception is "E. gingivalis"). Depending on the species, these can have one, four or eight nuclei and are variable in size; these characteristics help in species identification.

"Entamoeba" belongs to the Archamoebae, which are unusual in lacking mitochondria. This group also includes "Endolimax", which also lives in animals and is similar in appearance to "Entamoeba", although this may partly be due to convergence. Certain other genera of symbiotic amoebae, such as "Endamoeba", might prove to be synonyms of "Entamoeba" but this is still unclear.

Studying "Entamoeba invadens", David Biron of the Weizmann Institute of Science and coworkers found that about one third of the cells are unable to separate unaided and recruit a neighboring amoeba (dubbed the "midwife") to complete the fission. [cite journal | author = Biron D, Libros P, Sagi D, Mirelman D, Moses E | title = Asexual reproduction: 'Midwives' assist dividing amoebae | year = 2001 | journal = Nature | volume = 410 | pages = 430 | doi = 10.1038/35068628 | url = http://www.nature.com/nature/journal/v410/n6827/full/410430a0.html] He writes:

:"When an amoeba divides, the two daughter cells stay attached by a tubular tether which remains intact unless mechanically severed. If called upon, the neighbouring amoeba midwife travels up to 200 μm towards the dividing amoeba, usually advancing in a straight trajectory with an average velocity of about 0.5 μm/s. The midwife then proceeds to rupture the connection, after which all three amoebae move on."

They also reported a similar behavior in "Dictyostelium".


External links

* [http://homepages.lshtm.ac.uk/entamoeba/"Entamoeba" Homepage]
* [http://pathema.jcvi.org/cgi-bin/Entamoeba/PathemaHomePage.cgi Pathema-"Entamoeba" Resource]

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Look at other dictionaries:

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  • Entamoeba —   [zu griechisch entós »innen« und Amöben], Gattung der Amöben, die parasitisch oder als Kommensalen v. a. in Wirbeltieren leben. Wichtigste, beim Menschen vorkommende Arten sind: Entamoeba histolytica, der in zwei Modifikationen (der nicht… …   Universal-Lexikon

  • Entamoeba — Género de parásitos intestinales amebianos, varias de cuyas especies son patógenas para el hombre. También se denomina Entameba. Diccionario Mosby Medicina, Enfermería y Ciencias de la Salud, Ediciones Hancourt, S.A. 1999 …   Diccionario médico

  • entamoeba — en·ta·moe·ba (ĕn tə mēʹbə) also en·da·moe·ba (ĕn də ) n. pl. en·ta·moe·bas or en·ta·moe·bae ( bē) Any of several parasitic amoebas of the genus Entamoeba, especially E. histolytica, causing dysentery and ulceration of the colon and liver.   [New… …   Universalium

  • entamoeba — |ent+ noun Etymology: New Latin, from ent + Amoeba 1. capitalized, in some classifications : a genus of parasitic amoebas (family Endamoebidae) that includes those members of the genus Endamoeba which are parasites of vertebrates used chiefly in… …   Useful english dictionary

  • entamoeba — noun Etymology: New Latin Date: 1914 any of a genus (Entamoeba) of amoebas parasitic in vertebrates and including one (E. histolytica) that causes amebic dysentery in humans …   New Collegiate Dictionary

  • Entamoeba — A genus of ameba parasitic in the oral cavity, cecum, and large bowel of humans and other primates and in many domestic and wild mammals and birds; with the exception of E. histolytica, members of the genus appear to be relatively harmless… …   Medical dictionary

  • entamoeba — ent·amoeba …   English syllables

  • Entamoeba — n. a genus of widely distributed amoebae, of which some species are parasites of the digestive tract of humans. E. histolytica invades and destroys the tissues of the intestinal wall, causing amoebic dysentery and ulceration of the gut wall (see… …   The new mediacal dictionary

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