Amoeba

Diagram of amoeba structure

Amoeba (plural = amoebae) is a well known genus of unicellular organism, a protist. One of its most common species, the Amoeba Proteus, is about 0.2 to 0.3 mm large. The amoeba was first discovered by August Von Rosenhof in 1757. It is a genus of protozoa that moves with false feet, called pseudopodia.

The amoeba is a member of a whole group of amoeboid eukaryotic protists called Amoebozoa. They are heterotrophs, eating bacteria and other protists.

The pseudopodia (false feet) are extensions of the organism's cell membrane. They are used by the amoeba for phagocytosis (active food/nutrient intake) and motility (self-propelled movement).

Life

Amoebae are often found within freshwater, typically on vegetation in decay in still or slow moving water, or in the benthic zone of some lakes. However, they are common organisms of study because it is easy to keep them in a laboratory. They are used to study sex protozoa and to demonstrate cell structure and function.

Amoeba Media

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  Clockwise from top right: Amoeba proteus, Actinophrys sol, Acanthamoeba sp., Nuclearia thermophila., Euglypha acanthophora, neutrophil ingesting bacteria.

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  The forms of pseudopodia, from left: polypodial and lobose; monopodial and lobose; filose; conical; reticulose; tapering actinopods; non-tapering actinopods

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  Amoeba phagocytosis of a bacterium

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  Foraminifera have reticulose (net-like) pseudopods, and many species are visible with the naked eye

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  Neutrophil (white blood cell) engulfing anthrax bacteria

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  The first illustration of an amoeboid, from Roesel von Rosenhof's Insecten-Belustigung (1755)

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  Amoeba proteus with pseudopodia, cytoplasm often with truncated bipyramidal crystals. Nucleus large, mean 40 µm, discoid, often biconcave.

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  Trophozoites of the pathogenic Entamoeba histolytica with ingested red blood cells

Other websites

• Wikibooks: compare size of cells
• Amoeba info