Figure 1

The wild-type phenotype of P. morum. A vegetatively grown, ellipsoid spheroid of P. morum with ~16 cells. The cells are close together and even slightly narrowed at the inner end to appear keystone- or pear-shaped. Each cell has two flagella with two contractile vacuoles at their base, a single massive, cup-shaped chloroplast with at least one pyrenoid, and an eyespot. The cells are surrounded by a complex but transparent glycoprotein-rich extracellular matrix that holds all of the cells in place.