To experiment with fungi, mycologists often need to grow them. Simply allowing bread to become moldy is not an experiment. An experiment is the test of an idea. Often, this idea is expressed in the form of the question: what? What if...? What happens when...? What kind of effect...? Experiments are designed to use the methods and materials that will give the most complete and accurate answer to an inquiry.
Fungi break down and absorb organic material for their nourishment, so any experiment must first provide them with food. Oxygen and moisture are also necessary. A material for the growth of fungi for experiments is called a medium. Most commercially prepared media for growing fungi are extracts of plant materials like potatoes. A medium that is specially prepared to contain only the exact nutrients required by one species of fungus is called a "minimal medium".
The choice of growth medium depends on the question that is being asked. If the question is "What kinds of fungi grow naturally on bread?" the choice of medium is simple. You could just put a slice of bread in a plastic bag, close it to retain moisture and await mold growth.
However, observing only one slice of bread would not make an effective experiment. Your chosen slice may not have any mold spores on it, or contain spores of all the species present in the loaf. It might be too dry to allow growth. You would have to use a number of bags to account for all reasonably possible growth failures and successes. The slices of bread would be replicates. Replicates allow the treatment to be repeated often enough to allow you to determine if the results are significant or the product of random chance..
You will also need to decide how to record your results. Do you identify each species of mold by its scientific name, or do you just describe them (fluffy red colonies, white fuzzy spots, blue-green velvet, etc.?)
A more complicated question requires the design of a more complicated experiment. At first glance, "What effect does the preservative in some breads have on mold growth?" seems as if it could be answered with a loaf of bread and some plastic bags, like the first experiment. However, the best experiment on the effect of a preservative on mold growth would use two loaves of bread. These loaves would be identical in preparation and ingredients, except for the presence or absence of the preservative. The bread without the preservative would be the control and the bread containing the preservative would be the treatment. Replication of both treatment and control gives the experimenter a way to understand the effect of substance by showing what happens when it is both present and absent.
Last update: 19 Nov 06. © 1999. Robert Fogel, Ivins, UT 84731. Edited by Patricia Rogers.