Slime Mould, Physarum polycephalum
Qty: 1 inoculated plate
Physarum polycephalum is an unusual and fascinating organism that is ideal for classroom activities. This culture kit consists of one inoculated plain agar plate, one spare plain agar plate, rolled oat flakes to feed the Physarum, and includes notes and instructions.
Despite their rather unappealing name, slime moulds are fascinating and quite beautiful organisms. Known as Myxomycetes, they exhibit both plant-like and animal-like characteristics. A particularly interesting type is Physarum polycephalum, the Many-Headed Slime Mould.
In its growing stage, Physarum resembles a giant voracious amoeba that spreads out like a fan, enveloping everything in its path, and digesting any bacteria, spores and decaying organic matter it encounters. In this plasmodial stage, Physarum polycephalum is a bright yellow glistening mass that can grow to 30cm across under the right conditions. In response to environmental changes such as dry conditions or a scarcity of food, the plasmodium will begin to shrink and form fruiting bodies or sporangia. Germination of the spores leads to the formation of a new plasmodium and the cycle can begin again.
A curious variation occurs when the plasmodium encounters conditions that are too severe for it to continue growing, but not severe enough to cause it to form sporangia. It goes into a kind of dry dormant state called sclerotium that can revive itself if it becomes moist.
Physarum is easy and inexpensive to obtain and it can be easily cultured in the classroom on a moist substrate such as a plain agar plate. It can be fed rolled oats as it grows, and subcultured to a fresh plate when it has fully colonised the first. Even moist filter paper is suitable, but agar plates are easier to use because they do not need to be re-hydrated.
A dramatic behavioural characteristic of Physarum is cytoplasmic streaming. This can be easily seen by placing the culture plate on the microscope stage and using 40x magnification. Close down the diaphragm and focus on the bright yellow veins. The rapid fluid motion of the cytoplasm is easily observed. Note how the flow pauses every minute or so and reverses direction.
Physarum polycephalum is well suited to simple class activities because of its ability to migrate and respond to its environment. For example:
Students will learn how to frame their questions in ways that can be expressed as hypotheses and tested by controlled experiments.
Aside from scientific study, Physarum can be a source of inspiration for creative and descriptive writing. Try brainstorming a list of adjectives to describe the plasmodium.
Slime Mould - The Fungus That Walks - National Geographic, July 1981, page 131.
Chemotaxis in the Plasmodial Slime Mould, Physarum polycephalum - The American Biology Teacher, January 1998, page 59
The Fungus That Creeps - Creepy Crawlies and the Scientific Method, published 1993, chapter 7.