Exercise 13.5 - D.discoideum Growth on Agar
- Dictyosteleum discoideum grown axenically on agar plates
- Petri plates with SM agar media
- Broth culture of Klebsiella aerogenes
or E. coli (non-mucoid variety)
- Wire loop for transfers
- Microscope, slides, coverslips
- Select a petri plate with SM agar media, a broth culture of
and a culture of D. discoideum containing fruiting bodies.
- Inoculate an agar plate with a thin layer of the bacteria.
Select a fruiting body from the fungal culture and place it in
the center of the petri plate containing the bacterial
- Continue to monitor the growth of the fungus for the next
week (make daily observations - new fruiting bodies will appear
in about 4 days).
Note the initial germination of the spores from the fruiting
bodies, the subsequent growth and the increased number of amoeba
in the culture. As the culture begins to dry, the amoeba will
aggregate and form the migrating slug. The slugs will migrate
around the plate, consuming the bacteria as food.
Eventually, the slug will anchor itself to the agar and undergo a
process known as culmination. During this stage, the cells in the
anterior of the slug will begin differentiating into pre-stalk
cells, while those in the rear will develop into pre-spore cells.
- Sketch each stage in the development of the fungus and note
the time of each stage appearance within the culture.
Periodically remove a sample of the cells or slug and fix
with Carnoy fixative. Place the cells on a slide and allow to air
dry. Stain with a a basophilic dye and note any alterations in
the nuclear material during each phase. In particular, note the
presence and size of the nucleoli, and the degree of basophilia
demonstrated by the cytoplasm.
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Cell Biology Laboratory Manual
Dr. William H. Heidcamp, Biology Department, Gustavus Adolphus College,
St. Peter, MN 56082 -- firstname.lastname@example.org