Differences in the surface properties of the mating types of Physarum polycephalum

In the slime mold Physarum polycephalum, formation of a diploid plasmodium occurs when compatible haploid amoebae fuse. To study cell surface changes associated with the fusion process, a non-destructive method known as aqueous, two-phase partitioning was employed. Using a two-phase system of dextran and polyethylene glycol, we observed that the two mating types (RSD4 and MA185) have different partition coefficients and hence different surface properties. Based on their partitioning behavior, MA185 cells appear to have a more hydrophobic surface than RSD4 amoeba. The partition coefficient of both cell types decreased with time. If amoebae were maintained in culture until they encysted, differences in their surface were not detectable.