2 - A History of Research on Dictyostelium discoideum

Summary

The first description of Dictyostelium, by the mycologist Oskar Brefeld, is 130 years old (Brefeld, 1869). Many of the features of these organisms that modern workers assume to be obvious – the phagocytic nature of the amoebae, the separation of growth and developmental cycles, the absence of cell fusion in the aggregate – were not apparent to early workers. Culture systems had not been developed and the ease of manipulation that now makes these organisms so attractive would not be used until the 1930s by Kenneth Raper (Raper, 1937).

Brefeld (1869) first observed Dictyostelium mucoroides while examining the fungal flora in horse dung, and then grew purer cultures in rabbit dung. Even with this difficult culture method, Brefeld realized that the amoebae were the trophic (feeding) form, and that they aggregated to give rise to fructifications. He named the species Dictyostelium (Dicty means net-like and stelium means tower) because the aggregation territories he observed looked like nets (Fig. 2.1) and the fruiting bodies like towers (Fig. 2.2). He added the qualifier mucoroides because the new organism resembled the fungus Mucor. This was a misnomer because closer examination by Brefeld (1884) established that his new species did not have the same sporangial walls as the fungus, but instead the spores were suspended in a drop of liquid. The germination of the spores led not to hyphae and a mycelium but to distinctly amoeboid cells, which the microscopes of the time were quite capable of resolving.