Cultivating Slime Molds

Slime molds are primitive organisms that do not fit neatly into the categories of animal, vegetable, or mineral. They resemble both amoebae (single-cell organisms) and fungi. Like amoebae, slime molds are bloblike and move around to find food or avoid danger. Like a fungi, they release spores that feed on microorganisms and decaying organic matter. As the slime mold moves, it consumes food, produces waste, and grows. Slime molds like cool, moist conditions—you'll find them on the forest floor or on blades of grass, especially in locations where it is damp, such as near a streambed under a thick canopy of trees. Slime molds have a preference for upright objects, such as grass, tree stumps, and walls. Once you learn to recognize slime molds, you can collect and cultivate them.

There are over 450 known species of amoeboid slime molds. Myxomycophya is a common genus of slime mold. Some biologists argue that slime molds are neither plant nor animal, because they are unique in their structure and behavior.

Materials

• Petri dish (or inverted saucer or peanut butter jar lid)
• 2 Pyrex pie plates or a clear lidded casserole
• filter paper or paper towel (coffee filter paper)
• distilled water
• rubber tubing
• utility scissors
• metric ruler
• slime mold samples (You may be able to collect slime mold samples from a wooded area. You can also obtain slime mold cultures from a science equipment supplier. Transport your samples in a clean, dry jar, as quickly as possible.) Two suggested choices are Physarium polycephalum or Myxomycophyta.
• oats (Use old-fashioned rolled oats, not the "quick" variety.)
• notebook and pencil
• colored pencils
• assorted cereals or fruit
• assorted liquids (vinegar, rubbing alcohol, nail polish remover)
• eyedropper

Procedure

To Cultivate Your Slime Mold

Distilled water should be used to prevent contamination by other microorganisms or harmful minerals.

1. Place a Petri dish within a larger, clear, covered container, such as a casserole or a pair of facing Pyrex pie plates.
2. Lay a sheet of filter paper or a paper towel across the Petri dish. The paper should droop to the bottom of the dish.
3. Wet the paper thoroughly with distilled water, pouring off the excess. From time to time during the experiment, add enough water to prevent drying.
4. Make spacers from rubber tubing, using utility scissors to cut three or four 2.5-cm lengths of tubing. Pass the scissors through each piece of tubing, making one straight cut along the length so that you can pull the tubing open and fasten it to the rim of the pie plate as shown. Space the pieces evenly around the circumference to allow for a small air gap.
5. Place a small fragment of slime mold on the paper and wet it with a drop of water. Within a few hours the organism will awaken from its deathlike state. Keep the unused organisms in the refrigerator.
6. When the slime mold has emerged and has begun to seek food, put a flake of moistened uncooked oats in contact with the rapidly spreading growth.
7. Keep the covered dish at room temperature in an area that does not get direct sunlight. As the slime mold increases in size, place more oat flakes along the growth front. A rapidly moving specimen will consume a larger number of oat flakes than a sluggish one. In either case, the feeding organism will show a decided preference for fresh oat flakes and will abandon partially digested ones. Flakes that have first been moistened with a drop of water are accepted more readily than dry oats. To maintain a clean culture, transfer the organisms to a fresh sheet of filter paper or paper towel weekly, avoid overfeeding, and remove abandoned food that shows signs of becoming moldy or slimy.

To Perform Experiments on Your Slime Mold

In the early stage of growth, the myxomycete is like an animal, and generally consists of an unattractive patch of naked protoplasm (the contents of the nucleus of a living cell). Over time it develops colorful sporangia, or fruiting bodies, that release spores into the air. This is how this type of slime mold reproduces. The stage can be induced at any time by removing most of the food and allowing the myxomycete to roam while simultaneously keeping the organism moist. The transformation will occur suddenly, usually at night, within a week or two. If the observer is fortunate enough to witness the actual transformation, he or she will see the entire myxomycete, now more orange than yellow, appear to separate into uniformly rounded masses that ascend from the surface on stalks and then develop into weird, multilobed bodies.

1. What is the life cycle of your slime mold? Research this in depth and sketch what you believe corresponds to the different life stages in your slime mold. Keep a log with colored pencils.
2. Explore food preferences. What does your slime mold like to eat? Try different types of cereal or fruit (e.g., strawberries). Measure its rate of migration and compare its preferences for different foods.
3. Experiment with toxins and irritants: How does the slime mold respond to vinegar (acetic acid), rubbing alcohol (isopropyl alcohol), and nail polish remover (acetone)? Place a drop of each liquid next to the slime mold in three trials and study the slime mold's behavior.

References

Myxo web site: www.wvonline.com/myxo/

Introduction to the Slime Molds: www.ucmp.berkeley.edu/protista/slimemolds.html

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