Physarum

Physarum is a genus of slime molds in the family Physaraceae, within the class Myxogastria of the Amoebozoa. The best-known member is Physarum polycephalum, a large, bright yellow plasmodial slime mold widely used in research. It is not a true fungus, but a protist that forms a multinucleate feeding stage called a plasmodium.

The plasmodium is a single, multinucleate cell that can grow to several centimeters and moves by rhythmic cytoplasmic streaming through a network of protoplasmic tubes. It feeds on microorganisms in decaying vegetation. Under adverse conditions it can form a hardened sclerotium or produce sporangia that release spores, which germinate into swarm cells and reassemble into plasmodia. The organism exhibits negative phototaxis and tends to avoid bright illumination.

Physarum is typically found on decaying leaves, wood, and soil in moist, shaded habitats. It contributes to decomposition and nutrient cycling and can be observed in the forest litter layer and similar environments.

In science, P. polycephalum has been used to study basic cell biology, signaling, and behavioral adaptation. It has become a model for unconventional computation, with experiments showing that the plasmodium can optimize networks and solve mazes, inspiring Physarum-based algorithms for route planning and network design. In the laboratory, cultures are maintained on agar or oat flakes under humid conditions and are generally considered safe to handle in educational and research settings.