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Culmination in the slime mould Dictyostelium discoideum studied with a scanning electron microscope
Abstract:
Myxamoebae of Dictyostelium discoideum were allowed to develop on cellulose acetate filters, and specimens taken at various stages of fruiting body formation were prepared for study by scanning electron microscopy. In the immature fruiting body where the mass of pre-spore cells has just been lifted off the substratum by the developing stalk, the pre-spore cells are irregular in shape and are similar in appearance to cells in aggregates at earlier stages of development. As the stalk lengthens, the pre-spore cells gradually separate from one another and become rounded and elongate, but mature spores are not visible until the fruiting body reaches its maximum height. It is concluded that, contrary to previous reports, spore maturation is a slow process and is not completed until the sorus becomes pigmented. The mature stalk is surrounded by a smooth cellulose sheath but this does not envelop the cells of the basal disc, which remain discrete. The fruiting body is enclosed in a slime sheath and this may be important in holding together the mass of spores.
Insights
Spore maturation in Dictyostelium discoideum is a slow process, not completed until the sorus pigments. Scanning electron microscopy revealed cell shape changes during fruiting body development.
Area of Science:
- Cell Biology
- Developmental Biology
- Microscopy
Background:
- Dictyostelium discoideum is a model organism for studying cellular differentiation and development.
- Fruiting body formation involves complex cell sorting and morphogenesis.
Purpose of the Study:
- To investigate the morphological changes during Dictyostelium discoideum fruiting body formation using scanning electron microscopy.
- To clarify the timing and process of spore maturation.
Main Methods:
- Culturing Dictyostelium discoideum myxamoebae on cellulose acetate filters.
- Preparing specimens at various developmental stages for scanning electron microscopy.
Main Results:
- Pre-spore cells are irregular in immature fruiting bodies and become rounded/elongated as the stalk develops.
- Mature spores are only visible when the fruiting body reaches maximum height and the sorus becomes pigmented.
- The stalk has a cellulose sheath, while basal disc cells remain discrete; a slime sheath encloses the fruiting body.
Conclusions:
- Spore maturation is a gradual process, contrary to previous assumptions.
- The slime sheath may play a role in holding the spore mass together.