amoeba

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amoeba:

see amebaameba
or amoeba
, common name for certain one-celled organisms belonging to the phylum Sarcodina of the kingdom Protista. Amebas were previously classified as members of the animal kingdom.
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Amoeba

 

the order of the simplest organized protozoa of the class Sarcodina. Most live in fresh waters, a few in the soil; there are parasitic forms. They are usually of microscopic dimensions up to 50 μm, but there are also “giants” such as Pelomyxa, which grows to 2–3 mm. Amoebas have no constant body shape; their cytoplasmic body forms extrusions or pseudopodia which aid in motion and food gathering. They feed on bacteria, minute algae, and protozoa. The amoeba engulfs the food particle and from its cytoplasm the amoeba secretes digestive juices and forms a food vacuole within which the food is dissolved and is incorporated into the cytoplasm. The excretion of water (osmoregulation) and metabolic products occurs through the contractory vacuoles, which gradually accumulate waste matter and discharge it at the surface.

Amoebas ordinarily have one nucleus, but Pelomyxa is multinucleate. The majority of amoebas multiply asexually, dividing in two. The division of the body is preceded by mitosis in the nucleus. A sexual process is known only in very rare cases.

Upon subjection to unfavorable conditions—for instance, insufficient food, cold, or drying of the water body—the amoeba’s body becomes round and the surface of its cytoplasm becomes a dense protective layer; a cyst forms that is resistant to unfavorable effects of the dormant stage. Freshwater amoebas can serve as a water pollution index. Parasitic amoebas live in the intestines of various animals and man. Among these the most harmful is the dysentery amoeba (Entamoeba histolytica), which produces a severe form of amoebic dysentery in man. Infection occurs via cysts, which remain viable outside the human body.

REFERENCES

Dogel’, V. A., Iu. I. Polianskii, and E. M. Kheisin. Obshchaia protozoologiia. Moscow-Leningrad, 1962.
Seravin, L. N. Dvigatel’nye sistemy prosteishikh. Leningrad, 1967.

A. A. STRELKOV

Amoeba

[ə′mē·bə]
(invertebrate zoology)
A genus of naked, rhizopod protozoans in the order Amoebida characterized by a thin pellicle and thick, irregular pseudopodia.

amoeba

(US), ameba
any protozoan of the phylum Rhizopoda, esp any of the genus Amoeba, able to change shape because of the movements of cell processes (pseudopodia). They live in fresh water or soil or as parasites in man and animals

Amoeba

(operating system)
A distributed operating system developed by Andrew S. Tanenbaum and others of Vrije Universiteit, Amsterdam. Amoeba is only available under licence from the VUA, but is free of charge and includes all source, binaries and documentation.

http://am.cs.vu.nl/.

Amoeba

(computer, abuse)
A derogatory term for Commodore's Amiga personal computer.
References in periodicals archive ?
To the Editor: Primary amebic meningoencephalitis (PAM) is an acute and fulminant disease caused by Naegleria fowleri, an amphizoic ameba belonging to the family Vahlkampfidae.
El paciente asiste a controles posteriores observandose una respuesta pobre y lenta al tratamiento con empeoramiento de la agudeza visual por lo cual se decide tomar nueva muestra para estudio microbiologico, dos semanas posteriores a la primera toma y se obtiene reporte de trofozoitos de amebas de vida libre, compatibles con Acanthamoeba (figura 2).
Durante la infeccion, las amebas producen quistes que son eliminados de los intestinos junto con las heces.
La materia organica y biomasa microbiana producida en el sistema, es activamente consumida por diversos tipos de microorganismos eucarioticos bacteriovoricos, en especial, pequenos flagelados, amebas y ciliados adaptados a aguas con bajas concentraciones de sulfuro de hidrogeno.
Este sistema permite movimientos de contraccion en organismos como las amebas, los hongos mucilaginosos y celulas de los animales vertebrados (Grell, 1994).
died from a brain infection associated with primary amebic meningoencephalitis (PAM) after inhaling an ameba known as Naegleria fowleri while swimming in a central Florida lake this July.
Phylum 1 Archaeprotista (Amitochondriates, Amebas and Mastigotes without Mitochondria)
Un dia accidentalmente el profesor Persikov, quien trabaja en el Instituto Zoologico de Moscu, se da cuenta de los efectos de un rayo de luz sobre unas amebas que observa.
H20, SOIL, PLANTZ, AMEBAS, ZE REMOTE ARCTIK PLRBAER: ALLOFEM TAINTD.
The ubiquity of freeliving amebas and their parasitism by mimiviruses enhances the prospect that diverse environments could shelter these giant viruses (8-10).