|MadSci Network: Microbiology|
Like all living things, molds (or fungi) need certain things in order to grow. Among these are food, water, and proper temperature. Molds get their food by extracellular (outside the body) digestion, which is another interesting story which we won't go into today. Just like humans, molds are mostly water. Water is used in some processes, but all of the biochemical reactions necessary for life must take place in a watery solution (the cytoplasm) of the cell. (More on these reactions later.) The water environment of the cell allows all of the components to move and mix properly. It also prevents the mold from drying out, since water is critical for normal survival. As for temperature, molds are different from us. We control the temperature of our body so that all of the reactions have the proper conditions to go forward. We are called "warm blooded". Molds cannot control their temperature, so they must grow and develop at whatever temperature their environment is. In the watery solution inside mold cells are proteins called "enzymes" which direct the biochemical processes of the cells. These enzymes work faster when the temperature is higher (as long as it doesn't get too hot!) If you can do a growth experiment at several temperatures, you can probably find the temperature at which these enzymes work best for molds. For humans, it's 98.6 degrees Fahrenheit, which is our body temperature. (When biochemists take these enzymes out of the body, they still work best at 98.6 degrees.) For most molds, the optimal temperature is around 80 degrees. Molds do not need light for normal growth, because they do not make their own food like plants do. Molds are eating (using extracellular digestion) food that was at some point produced by plants. At some point in their life, most molds do need light to start a different life stage, such as spore production. The main reason for growing molds in the dark is that they might get dried out by sun or other bright lights.
Try the links in the MadSci Library for more information on Microbiology.