The developmental capacity of various stages of a macrocyst-forming strain of the cellular slime mold, Dictyostelium mucoroides.

Vegetative cells of certain strains of Dictyostelium mucoroides form fruiting bodies on an agar surface and macrocysts when placed under saline. This study sought to determine whether the aggregation and pseudoplasmodial stages of fruiting body formation could be induced to form macrocysts when placed under saline. Likewise, different stages in macrocyst formation were put on an agar surface to determine their potential to switch to fruiting body formation. It was found that 78% of the aggregates and 21% of the pseudoplasmodia placed under saline formed macrocysts indicating that as fruiting body development proceeds, there is a restriction of the capability of cells to respond to environmental conditions favoring macrocyst formation. Stages in macrocyst development prior to the formation of precysts always formed fruiting bodies when put on agar. Once precysts had formed, surrounded by their acellular sheath, they always developed as macrocysts on agar. Peripheral cells isolated from precysts and put on agar quickly aggregated; the aggregates became surounded by a sheath and developed as macrocysts. If isolated peripheral cells were allowed to proliferate on the agar surface, the resulting cells aggregated and formed fruiting bodies.