Algae: Phototrophic eukaryotic microorganisms Fungi: Nonphotosynthetic eukaryotic microorganisms that contain rigid cell walls Slime molds: nonphototrophic eukaryotic microorganisms that lack cell walls and that aggregate to form fruiting structures (cellular slime molds) or masses of protoplasm (acellular slime molds) Protozoa: unicellular eukaryotic microorganisms