Re: Does light affect the speed that mold grows on cheese?

In general light does not have much effect on the speed at which mold grows. With the same food source and same temperature, they will grow at pretty much the same rate. The main effect light (especially sunlight) has on mold growth is to dry them out, which stops the growth. On the kitchen counter in a covered container where the mold and its food can stay nice and humid(but not wet), it will grow just fine.

Even though molds don't need light to grow, light does have an effect on them. Light can affect the way in which they grow (their shape, color, making spores). Here is a simple experiment you can do to see if light has an effect on your mold.

Set up three identical substrates (the food on which you want the mold to grow--a slice of cheese or bread for instance) and put a little spot of mold from moldy bread or cheese on each one with a toothpick. Then put each in a container so they won't dry out (food storage bag or sandwich box works well). Put one in the dark closet, and leave one on the counter with the light on all day and night. For the third one, leave it on the counter during the day, then put it in the closet at night. Check them after a few days, when you can see a couple of inches of growth on the one which stays in the light. (Be sure the closet and counter are close to the same temperature and if you use bread, it helps if there are no preservatives in it. The preservatives slow down the mold growth, which is usually a good thing for bread, but not for a moldy growth experiment!)

I must tell you that the last time I did this experiment, nothing grew at all the first time, so I had to do it again. It should grow on all three, but they should look different. Good luck and let me know how it turns out.

For more information on molds check out:
http://www.ucmp.berkeley.edu/fungi/fungi.html
(especially the Fun Facts)