amoebae

アメーバ

関

ameba、amebae、amoeba

WordNet

1. naked freshwater or marine or parasitic protozoa that form temporary pseudopods for feeding and locomotion (同)amoeba

PrepTutorEJDIC

1. =ameba

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2012/12/16 20:05:42」(JST)

wiki en

[Wiki en表示]

Foraminiferan (Ammonia tepida)

Amoeboids are single-celled life-forms characterized by an irregular shape.

"Amoeboid" and "amœba" are often used interchangeably even by biologists, and especially refer to a creature moving by using pseudopodia. Most references to "amoebas" or "amoebae" are to amoeboids in general rather than to the specific genus Amoeba. The genus Amoeba and amoeboids in general both derive their names from the ancient Greek word for change.

Structure

Amoeboids move using pseudopodia, which are bulges of cytoplasm.

Amoebas breathe using their entire cell membrane that is constantly immersed in water. Excess water can cross into the cytosol. Amoebas have a contractile vacuole to expel excess water.

Food sources vary in amoeboids. They may consume bacteria or other protists. Some are detritivores and eat dead organic material. They extend a pair of pseudopodia around food. They fuse to make a food vacuole which then fuses with a lysosome to add digestive chemicals. Undigested food is expelled at the cell membrane.

Amoebas use pseudopodia to move and feed. They are powered by flexibe microfilaments near the membrane. Microfilaments are at least 50% of the cytoskeleton. The other parts are more stiff and are composed of intermediate filaments and microtubules. These are not used in amoeboid movement, but are stiff skeletons on which organelles are supported or can move on.

The shells of amoebas are often composed of calcium. The proteins or materials are synthesised in the cell and exported just outside the cell membrane.

Multicellular amoebas: Slime molds

Main article: Slime mold

Amoebas seem to have connections with two phyla (now defunct) composed of multicellular organisms of the lineage of fungus-like protists, the so-called slime molds. These two defunct phyla were the Myxomycota (i.e., plasmodial slime molds, now classified in the taxon Myxogastria), and Acrasiomycota (i.e. cellular slime molds, now divided into the taxa Acrasida and Dictyosteliida). These two phyla use amoeboid movement in their feeding stage. The former is basically a giant multinucleate amoeba, while the latter lives solitary until food runs out; in which a colony of these functions as a unit. Myxomycete slime molds use amoeboid gametes, as well.

Diversity

They have appeared in a number of different groups. Some cells in multicellular animals may be amoeboid, for instance human white blood cells, which consume pathogens. Many protists also exist as individual amoeboid cells, or take such a form at some point in their life-cycle. The most famous such organism is Amoeba proteus; the name amoeba is variously used to describe its close relatives, other organisms similar to it, or the amoeboids in general.

Classification

As amoebas themselves are polyphyletic and subject to some imprecision in definition, the term "amoeboid" does not provide identification of an organism, and is better understood as description of locomotion.

When used in the broader sense, the term can include many different groups. One source includes 97 different genera. Others include far fewer.

Older classification

In older classification systems, amoeboids, under the taxon name Sarcodina, had been divided into several morphological categories based on the form and structure of their pseudopods.

Amoeboids with pseudopods supported by regular arrays of microtubules were called actinopods, whereas those that weren't were called rhizopods, which were further subdivided into lobose, filose, and reticulose amoebae. In contrast to "rhizopods", where most of their morphologies can be mapped to modern classification systems, "actinopods" appear to be extensively polyphyletic. Actinopods are divided into radiolaria and heliozoa (itself a polyphyletic grouping).

Finally, there was also a strange group of giant marine amoeboids, the xenophyophores, that did not fall into any of these categories.

Modern classification

More modern classifications are based upon cladistics. It has been stated that most amoeboid are now grouped in Amoebozoa or Rhizaria. However, in contexts where "amoeboid" is defined more loosely, there are many amoeboid species that are in the Excavata clade.

Phylogenetic analyses place these genera into the following groups (not all of these are considered amoeboid (or "amoebas") by all sources):

Grouping	Genera	Morphology
Amoebozoa	Lobosea: Acanthamoeba, Amoeba, Balamuthia, Chaos, Clydonella, Discamoeba, Echinamoeba, Filamoeba, Flabellula, Gephyramoeba, Glaeseria, Hartmannella, Hydramoeba, Korotnevella (Dactylamoeba), Leptomyxa, Lingulamoeba, Mastigina, Mayorella, Metachaos, Neoparamoeba, Paramoeba, Polychaos, Phreatamoeba, Platyamoeba, Protoacanthamoeba, Rhizamoeba, Saccamoeba, Sappinia, Stereomyxa, Thecamoeba, Trichamoeba, Trichosphaerium, Unda, Vannella, Vexillifera Conosa: Endamoeba, Entamoeba, Hyperamoeba, Mastigamoeba, Mastigella, Pelomyxa	Lobose pseudopods (Lobosea): Lobose pseudopods are blunt, and there may be one or several on a cell, which is usually divided into a layer of clear ectoplasm surrounding more granular endoplasm.
Rhizaria	Cercozoa: Filosa: Monadofilosa: Gyromitus, Paulinella Granofilosea: Endomyxa: Proteomyxidea: Vampyrella Gromiidea Ascetosporea Foraminifera Radiolaria	Filose pseudopods (Filosa): Filose pseudopods are narrow and tapering. The vast majority of filose amoebae, including all those that produce shells, are placed within the Cercozoa together with various flagellates that tend to have amoeboid forms. The naked filose amoebae also includes vampyrellids. Reticulose pseudopods (Endomyxa): Reticulose pseudopods are cytoplasmic strands that branch and merge to form a net. They are found most notably among the Foraminifera, a large group of marine protists that generally produce multi-chambered shells. There are only a few sorts of naked reticulose amoeboids, notably the gymnophryids, and their relationships are not certain. Radiolarians are a subgroup of actinopods that are now grouped with rhizarians.
Excavata	Heterolobosea: Vahlkampfiidae: Monopylocystis, Naegleria, Neovahlkampfia, Paratetramitus, Paravahlkampfia, Psalteriomonas, Sawyeria, Tetramitus, Vahlkampfia, Willaertia Gruberellidae: Gruberella, Stachyamoeba Parabasalidea: Dientamoeba, Histomonas Other: Rosculus, Acrasis, Heteramoeba, Learamoeba, Stygamoeba, Plaesiobystra, Tulamoeba	The Heterolobosea, includes protists that can transform between amoeboid and flagellate forms.
Chromalveolate	Heterokont: Hyalodiscus, Labyrinthula Alveolata: Pfiesteria	Hyalodiscus and Pfiesteria are sometimes considered to have amoeboid characteristics.
Nucleariid	Micronuclearia, Nuclearia	Nucleariids appear to be close relatives of animals and fungi.
Ungrouped/ unknown	Adelphamoeba, Astramoeba, Cashia, Dinamoeba, Flagellipodium, Flamella, Gibbodiscus, Gocevia, Hollandella, Iodamoeba, Malamoeba, Nollandia, Oscillosignum, Paragocevia, Parvamoeba, Pernina, Pontifex, Protonaegleria, Pseudomastigamoeba, Rugipes, Striamoeba, Striolatus, Subulamoeba, Theratromyxa, Trienamoeba, Trimastigamoeba, Vampyrellium

Pathogenic interactions with other organisms

Some amoeboids can infect other organisms pathogenically (causing disease):

• Entamoeba histolytica is the cause of amoebiasis, or amoebic dysentery.
• Naegleria fowleri (the "brain-eating amoeba") is a fresh-water-native species that can be fatal to humans if introduced through the nose.
• Acanthamoeba can cause amoebic keratitis and encephalitis in humans.
• Balamuthia mandrillaris is the cause of (often fatal) granulomatous amoebic meningoencephalitis

References

External links

• The Amoebae website brings together information from published sources.
• Amoebas are more than just blobs
• Sun Animacules and Amoebas
• Molecular Expressions Digital Video Gallery: Pond Life - Amoeba (Protozoa) Some good, informative Amoeba videos.
• Amoebae: Protists Which Move and Feed Using Pseudopodia at the Tree of Life web project

English Journal

• Intracellular killing of bacteria: is Dictyostelium a model macrophage or an alien?

• Cosson P1, Lima WC.
• Cellular microbiology.Cell Microbiol.2014 Jun;16(6):816-23. doi: 10.1111/cmi.12291. Epub 2014 Apr 4.
• Predation of bacteria by phagocytic cells was first developed during evolution by environmental amoebae. Many of the core mechanisms used by amoebae to sense, ingest and kill bacteria have also been conserved in specialized phagocytic cells in mammalian organisms. Here we focus on recent results rev
• PMID 24628900

• Characterization of isolates of Acanthamoeba from the nasal mucosa and cutaneous lesions of dogs.

• Carlesso AM1, Mentz MB, da Machado ML, Carvalho A, Nunes TE, Maschio VJ, Rott MB.
• Current microbiology.Curr Microbiol.2014 Jun;68(6):702-7. doi: 10.1007/s00284-014-0532-9. Epub 2014 Feb 5.
• Acanthamoeba spp. are free-living amoebae that are ubiquitously distributed in the environment and can cause encephalomyelitis in animals and humans. The factors that contribute to Acanthamoeba infections include parasite biology, genetic diversity, environmental spread, and host susceptibility. The
• PMID 24496873

• Inefficacy of marketed contact lens disinfection solutions against keratitis-causing Acanthamoeba castellanii belonging to the T4 genotype.

• Lakhundi S1, Khan NA1, Siddiqui R2.
• Experimental parasitology.Exp Parasitol.2014 Jun;141:122-8. doi: 10.1016/j.exppara.2014.03.018. Epub 2014 Mar 21.
• The aim of this study was to assess the anti-amoebic effects of marketed contact lens disinfecting solutions. Using amoebistatic, amoebicidal, and cysticidal assays, nine different contact lens solutions were tested including: ReNu MultiPlus, DuraPlus, Ultimate Plus, OptiFree Replenish, OptiFree Exp
• PMID 24657584

Japanese Journal

• Amoebal Endosymbiont Neochlamydia Genome Sequence Illuminates the Bacterial Role in the Defense of the Host Amoebae against Legionella pneumophila

• Ishida Kasumi,Sekizuka Tsuyoshi,Hayashida Kyoko,Matsuo Junji,Takeuchi Fumihiko,Kuroda Makoto,Nakamura Shinji,Yamazaki Tomohiro,Yoshida Mitsutaka,Takahashi Kaori,Nagai Hiroki,Sugimoto Chihiro,Yamaguchi Hiroyuki
• PLoS ONE 9(4), e95166, 2014-04-18
• … Previous work has shown that the obligate intracellular amoebal endosymbiont Neochlamydia S13, an environmental chlamydia strain, has an amoebal infection rate of 100%, but does not cause amoebal lysis and lacks transferability to other host amoebae. … Taken together, the genomic features of Neochlamydia S13 explain the intimate interaction with the host amoeba to compensate for bacterial metabolic defects, and illuminate the role of the endosymbiont in the defense of the host amoebae against Legionella infection. …
• NAID 120005425332

• Testate Amoebae of the Imperial Palace, Tokyo (皇居の生物相(2)動物相)

• 島野 智之,Bobrov Anatoly,Mazei Yuri
• 国立科学博物館専報 (50), 21-28, 2014-03
• NAID 40020056688

• Isolation of Acanthamoeba Genotype T4 from a Non-Contact Lens Wearer from the Philippines

• Buerano Corazon C.,Trinidad Abigail D.,Fajardo Lindsay Sydney N.,Cua Irwin Y.,Baclig Michael O.,Natividad Filipinas F.
• Tropical Medicine and Health 42(4), 145-147, 2014
• … Molecular identification of the amoebae at the genus level based on the presence of Acanthamoeba-specific amplimer S1, ASA.S1 confirmed the morphological identification. …
• NAID 130004678281

Related Links

• Amoebae | インターネット内の検索結果 | cyclopaedia.net

ウィキペディアの英語版でAmoebaeという用語が挙げてありますが、そこでは、以下の意味で使われています。Amoeboids are single-celled life-forms characterized by an irregular shape. "Amoeboid" and "amœba" are often used ...

• Amoebae | Define Amoebae at Dictionary.com

noun, plural amoebas, amoebae / əˈmi bi / Show Spelled [uh-mee-bee] Show IPA. ameba. ... amoeba or ameba (əˈmiːbə) —n, pl-bae, -bas any protozoan of the phylum Rhizopoda, esp any of the genus Amoeba, able to change ...

---

★リンクテーブル★

リンク元	「アメーバ」「ameba」「amebae」
関連記事	「amoeba」

「アメーバ」

　　[★]

英

ameba、amebae、(古)amoeba、(古)amoebae

関

アメーバ目

「ameba」

　　[★] アメーバ

関

amebae、amoeba、amoebae、Amoebida

　

「amebae」

　　[★]

アメーバ

関

ameba、amoeba、amoebae

「amoeba」

　　[★]

アメーバ

関

ameba、amebae、amoebae、Amoebida