Dictyostelium discoideum
(gcide) | slime mold \slime mold\, slime mould \slime mould\n.
1. An unusual fungus-like protist of the phylum Myxomycota or
the class Myxomycetes, having a stage of growth in which
it comprises a naked noncellular multinucleate mass of
creeping protoplasm having characteristics of both plants
and animals; it also has a propagative phase in which it
develops fruiting bodies bearing spores; it is sometimes
classified as a protist. It is called also {acellular
slime mold}. [WordNet 1.5 +PJC]
2. Any of several remarkable amoebalike organisms of the
phylum Acrasiomycota, mostly terrestrial, having a
fruiting phase resembling that of the {acellular slime
molds}, but being cellular and nucleate throughout their
life cycle; called also cellular slime mold. The most
studied species is Dictyostelium discoideum. In their
feeding phase, they live like amoebae as individual cells,
engulfing bacteria as a prime food source. When the food
source diminishes, they begin to aggregate, swarming
together to form clumps which may move toward heat and
light, so as to reach the surface of the ground; they then
differentiate into a form with spores contained within a
sporangium resting on a stalk. When the spores are carried
to another location with adequate food supplies, the
spores may germinate to resume the life cycle. The phase
of aggregation appears to be initiated by release of
cyclic AMP, serving as a signal between the individual
cells. The formation of the fruiting body has some
similarities to differentiation in multicellular
organisms, but the mechanisms are still under study. Some
biologists object to the classification of Dictyostelium
as a slime mold, as it is neither a mold nor slimy.
[PJC] |