Participation of the cell surfaces determining the developmental courses in the cellular slime mould dictyostelium purpureum.

Dictyostelium purpureum S5 and S6, mating type strains, form fruiting-bodies in a monoclonal culture, but product macrocysts in a mix culture. The effects of Concanavalin A (Con A) on both fruiting-body formation and macrocyst formation, and changes of Con A-mediated cell agglutinability during development were studied. It was found that Con A inhibits macrocyst formation but not fruiting-body formation, and that macrocyst-forming cells are much more susceptible to Con A agglutination than are fruiting-body-forming cells during the aggregation stages. When fruiting-body-forming cells are treated with either trypsin or alpha-chymotrypsin, their Con A agglutinability is enhanced to the same extent as that of macrocyst-forming cells. It was also found that when S6 cells are treated with proteases they sometimes produce normal macrocysts even in a monoclonal culture. The results obtained in these experiments showed that the surface properties of fruiting-body-forming cells and macrocyst-forming cells are different, and that the cell surface might play an important role in determining the two developmental courses.