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From Wikipedia, the free encyclopedia
The dictyostelids are a group of cellular slime moulds. When food (normally bacteria) is readily available they take the form of individual amoebae, which feed and divide normally. However, when the food supply is exhausted, they aggregate to form a multicellular assembly, called a pseudoplasmodium or slug (not to be confused with slug the animal). The slug has a definite anterior and posterior, responds to light and temperature gradients, and has the ability to migrate. Under the correct circumstances the slug matures forming a fruiting body with a stalk supporting one or more balls of spores. These spores are inactive cells protected by resistant cell walls, and become new amoebae once food is available.
Dictyostelids | |
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Scientific classification | |
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Order: | Dictyosteliida |
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Dictyosteliidae
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In Acytostelium, the fruiting body is supported by a stalk composed of cellulose, but in other dictyostelids the stalk is composed of cells, sometimes taking up the majority of the original amoebae. With a few exceptions, these cells die during stalk formation, and there is a definite correspondence between parts of the slug and parts of the fruiting body. Aggregation of amoebae generally takes place in converging streams. The amoebae move using filose pseudopods, and are attracted to chemicals produced by other amoebae. In Dictyostelium, aggregation is signalled by cAMP, but others use different chemicals. In the species Dictyostelium purpureum, the grouping is by kinship, not just by proximity.
Dictyostelium has been used as a model organism in molecular biology and genetics, and is studied as an example of cell communication, differentiation, and programmed cell death. A large body of research data concerning D.discoideum is available on-line at DictyBase.