28 Apr 2010

Understanding Cellular Slime Mold/ Dictyostelida

Research carried out for purposes of  art related project

For al those who said nothing is clear, maybe this post will help.
The cellular slime molds (Dictyostelida) straddle the line between individuality and multicellularity.

How they move?
­­Slime molds feed and move via pseudopodia, like amoeba, Pseudopodia - A temporary projection of the cytoplasm, or of certain unicellular organisms, especially amoebas.
Most cellular slime molds lack flagellated stages(long, threadlike appendage)

Defining a Dictiostelid cellular slime molds


OHN C. LANDOLT
Dictyostelid cellular slime molds (dictyostelids) are singlecelled,

eukaryotic,( A cell with a membrane-bound nucleus.)

phagotrophic ( feed by ingesting/swallowing particulate organic carbon or intact [whole] cells )
bacterivores (free-living, generally heterotrophic [an organism that obtains its energy through consuming other organisms] organisms, )

move and feed in an amoeboid manner: by temporarily projecting cytoplasm.

Exclusively microscopic, which obtain energy and nutrients from the consumption of bacteria. present in terrestrial (earth) ecosystems.

These organisms represent a normal component of the

microflora in soils (earth, dirt) and apparently play a role in maintaining
the natural balance that exists between bacteria and other

microorganisms in the soil environment.
The Life Cycle of a Dictyostelium slime mold:

(The asexual reproduction)

(there also are myxomycetes and protostelids slime molds, but we are given dictiostelium slime mold life cycle)
The dominant stage in a cellular slime mold is the haploid stage.
For most of their life cycle, dictyostelids exist as independent, amoeboid cells (myxamoebae) that

feed upon bacteria,
grow,
and multiply by binary (double ) fission (splitting)

When the available food supply within a given microsite becomes depleted, numerous myxamoebae aggregate to form a structure called a pseudoplasmodium,








Within each cell maintains its individual integrity (wholesomness)
aggregate consists of up to 100,000 cells

The multicellular aggregate secretes material that forms a sheath around the entire structure, which forms a tower of cells.




the absence of light the tower topples and migrates as a single organism, The slug resembles a blob of petroleum jelly, leaving a trail of slime as it migrates.

video

As the fruiting body forms, the cells differentiate into a base, stalk, and apical mass containing encapsulated spores

the pseudoplasmodium then produces one or more fruiting bodies (sorocarps) bearing spores ( see previous video)
Fruiting bodies may take the shape of tiny goblets, globes, plumes

Under favorable conditions, the spores germinate (grow) to release myxamoebae (the same singe cell of the migragting colony)

and the life cycle begins anew.

Wher are they found :

Dictyostelids are most abundant in the surface humus layer of forest soils

Few studies have associated dictyostelids with caves

Few of the species Found in caves:
Dictyostelium caveatum
Dictyostelium mucoroides
Dictyostelium rosarium
Dictyostelium Giganteum
Dictyostelium aureo-stipes,
Dictyostelium . purpureum
Least common:
Dictyostelium citrinum,
Dictyostelium macrocephalum
Dictyostelium polycephalum
( the given species are examples from caves , there are lots more of dictyuostelium species )

Depending upon the particular cave, samples ranged in texture from powdery dry dust or gravel (stones) to very wet clay mud.

To give one particular example of cellular slime mold, I chose D. Caveantum

The spectacular D. Caveatum (Dictyostelium caveatum)


D.caveatum is a member of the dictiostelids , ( "slime moulds" or "social amoebae"). It consists of a single cell and its rather unassuming amoeba-like appearance hides the fact that it is a predator par excellence. it has highly effective ways of killing its prey - other very closely related social amoebae.
If a group of 10,000 D.discoideum cells is invaded by even a single D.caveatum one, they are doomed. The lone invader eventually eats the other species, using their cells as fuel to produce its own fruiting bodies.
After 48 hours, only D.caveatum remains.
single D.caveatum can consume a group of tens of thousands of other amoebae, before it can form a fruiting body.
The signaling to gather into a colony
Spiral geometry of a signal transmitter in an amoeba population (Dictyostelium discoideum) leads to chemotactic movements of cells in direction of the spiral core.
And this is the video illustrating the process from signalling to the gathering to migrating colony








5 comments:

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