amoeba

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Related to amoebas: ameba, amoebiasis, Diatoms

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 ?
Then, evolution stopped again because the amount of membrane an amoeba can contain also has a size limitation.
The amoeba made different amounts of proteins in each stage, suggesting that it was responding to new demands.
Naegleria fowleri is a thermophilic amoeba that grows well in tropical climates7.
Two Louisiana residents died in 2011 from an infection caused by an amoeba that was likely delivered directly to their brains via a neti pot, a device that some people use to flush out their sinuses.
Like Mimivirus, Megavirus has hair-like structures, or fibrils, on the exterior of its shell, or capsid, that probably attract unsuspecting amoebas looking to prey on bacteria displaying similar features.
Thus, the amoebas can prevent the attachment of the host's surface proteins, collect them, and then effectively shed the membrane.
When there are plenty of edible bacteria around, the amoebas ooze around and dine by themselves.
The symbiotically dependent amoebas developed into an undeniably separate species, because attempts to interbreed with the parent stock would infect and kill them.
Amoebic dysentery is particularly common in countries without reliable sanitation, such as in South East Asia, South America and parts of Africa, because the amoeba spreads through infected water.
It also stands to reason that there are a few amoebas wondering if there are other amoebas out there in the universe.
Primers designed to SSU rRNA sequences of the lobster amoeba and other paramoebid/vexilliferid amoebae were used in a nested polymerase chain reaction (PCR) protocol to test DNA extracted from formalin-fixed paraffin-embedded tissues of lobsters collected during the 1999 die-off, when this amoeba initially was identified by light and electron microscopy and reported to be a paramoeba of the genera Paramoeba or Neoparamoeba (Mullen et al.
Byers was a member of the Society of Protozoology, the American Society of Microbiology, and founder of the International Conference on Free-living Pathogenic Amoebas.