Introduction: (Initial Observation)
Fungi are a kingdom of heterotrophic single-celled, multinucleated, or multicellular organisms, including yeasts, molds, mildew and mushrooms. Previously classified in the plant kingdom, fungi are nonmotile, like plants, but lack the vascular tissues (phloem and xylem) that form the true roots, stems, and leaves of plants.
Fungi are parasites and obtain their nourishment from another living organism called the host.
Other than a few edible types of mushrooms, most fungi are considered disease for their host. For example apple powdery mildew is a known disease for apple trees. Other fruits also get infected with similar type of fungi. Fungi can also infect human skin.
In this project, we research the conditions that are favorable for fungi growth. The result of this study and many other similar studies on fungi can help us to reduce or prevent growing fungi on trees, crops, and skin. We can also use the same information to grow mushrooms and other types of fungi needed for food or pharmaceutical uses.
What you will see in this project is just an example of information and experiments about growing fungi. You need to read this information and then come up with your own procedures. First you will decide what type of fungi you want to study on. Mold is an easy one, but you may select mushroom, yeast, mildew or anything else. The next step is growing some fungi of the type that you select in order to make yourself familiar with what is involved. In your final step, you will repeat growth experiment at different conditions of light, moisture, and temperature. Finally, you will compare the results and draw a conclusion.
Find out about fungi, how they grow, and where they grow. Read books, magazines or ask professionals who might know in order to learn about different types of fungi. Keep track of where you got your information from.
To view the photographs, click on the thumbnails below. After viewing the individual photographs, please close your browser window to return to this page.
The 100,000 identified species of organisms commonly classed together as fungi are customarily divided into four phyla, or divisions: Zygomycota, Ascomycota, Basidiomycota, and Deuteromycota.
Also search the internet for “fungi infection”. Some of these sites also offer information on how to avoid fungi. Almost all prevention methods include changing the conditions to the one that is not good for fungi growth.
About Mold Experiment
As you know, we keep food in refrigerators so it will last longer. But still, sometimes you open a bag of bread or a jar of spaghetti sauce and what do you find? Mold!!
Ever wonder exactly what mold is? And how did it get there? And why sometimes it’s green and other times black or white? Did you know mold is a fungus and is alive and growing?
In this experiment, you’ll find out all about those colorful, fuzzy fungi by growing your own crop.
Print out these pages and follow the directions to do this experiment at home. When you’re done, try answering
the questions below.
Note: This is a long-term activity. It will take several days for the mold to grow. The first day should take you about 30 minutes to one hour to prepare everything. For safety reasons, don’t eat or drink while doing this experiment. And don’t taste or eat any of the materials used in this activity.
- 3 eye droppers
- small cup filled with 4 teaspoons or 20 mL of sugar water (see directions for preparing sugar water below)
- small cup filled with 4 teaspoons or 20 mL lemon juice
- small cup filled with 4 teaspoons or 20 mL tap water
- 4 slices of plain white bread*
- 4 slices of assorted bread, such as wheat, rye, sourdough, etc.*
- 8 resealable plastic sandwich bags
- masking tape
*It’s best if you use newly bought, fresh bread to make this experiment as accurate as possible.
Preparing sugar water
Note: Young people who don’t have experience operating a stove or microwave oven should get help and supervision from an adult. Parents or supervisors of young children may consider doing this step themselves.
Microwave: Stir 1/4 cup of sugar into 1/4 cup of water in a microwave-safe container and heat at one-minute intervals until sugar dissolves. Water will not need to reach boiling. Use potholders or oven mitts to handle container. Allow the mixture to cool for about five minutes before using.
Stovetop: Stir 1/4 cup of sugar into 1/4 cup of water in a small saucepan. Heat over medium heat until the sugar is dissolved. Use potholders to handle hot saucepan. Allow the mixture to cool for about five minutes before using.
What To Do:
1. Using masking tape and marker, make labels for four sandwich bags. Label the first bag “Dry White Bread.” Label the second “Water on White Bread,” the third “Lemon Juice on White Bread,” and the fourth “Sugar Water on White Bread.”
2. Wash your hands. Place a slice of white bread in the bag labeled “Dry White Bread” and seal the bag. Using one eye dropper, sprinkle 20 drops of tap water on another slice of white bread. (Don’t overdo it; the bread should be moist, not wet. If your bread is dripping, you’ve definitely done way too much. Throw away that slice and try again.) Place the moist bread in the bag marked “Water on White Bread” and seal the bag. Using a different eye dropper, sprinkle 20 drops of lemon juice on another slice of white bread and put it in the bag marked “Lemon Juice on White Bread” and seal the bag.
Using your third eye dropper, sprinkle 20 drops of sugar water on the last slice of white bread and place it in the bag labeled “Sugar Water on White Bread” and seal. Try to keep your fingers off moist spots when handling each slice of bread.
3. Repeat steps 1 and 2, but this time use a different kind of bread in the remaining four bags. Your labels should note what kind of bread you’re using. Wash your hands when you’re done.
4. Make sure all of your bags are tightly sealed. Place all eight bags in a dark, warm place (about 86 degrees Fahrenheit, 30 degrees Celsius). Check with your parents or supervisor about where to store the bags. Check the bags each day for two weeks and record the results in a notebook. You may wish to draw or take pictures of the bread slices. Don’t open the bags!
5. Make a graph recording the total growth of mold on each of the four white bread slices at the end of two weeks (see sample graph on right). Make a similar graph for the other four bread slices. Compare the results. At the end of the two weeks, throw out all the bags unopened.
- From this activity can you tell what helps mold to grow best?
- Does it matter what kind of bread you use?
- What causes the different colors you see?
- What would happen if you left the bags in a well-lit place instead of a dark place?
- What would happen if you changed the temperature?
Answer 1: Unless you used bread that had been sitting out for many days, you probably didn’t get much or any mold growth on the dry bread. Clearly, water is important for the growth of mold. The mold grew best on bread sprinkled with sugar water because the sugar serves as food for the fungi. The more food that’s available, the more fungi cells can grow. The mold also grew pretty well on the bread with plain tap water because the fungi could use the sugar and starch in the bread as food. The mold didn’t grow as well on the bread sprinkled with lemon juice because lemon juice is acidic. Acids hinder the growth of many common fungi and bacteria.
Answer 2: Molds grow better on some kinds of breads than others depending on the ingredients used and how the bread was made. Some breads are dry and some are moist. The amount of the sugar in different breads varies; some have sugar, honey or molasses added. Some breads are even acidic, such as sourdough. Some may have fruit or nuts or other ingredients added. Many commercial breads are made with preservatives that hinder the growth of molds and bacteria to prevent or delay spoilage. Bread baked fresh in a bakery that doesn’t use preservatives will more likely become moldy faster. All of these factors can influence how much mold will grow on a particular kind of bread.
Answer 3: Many of the colors you see on the moldy bread are due to the spores the fungi have produced. Molds reproduce by making spores at the end of stalks that rises above the surface of the bread, giving molds a fuzzy appearance. Spores are like seeds—they spread molds to new places so that they can continue to grow. Spores are usually colorful. Some fungi, such as Rhizopus nigricans (rye-zoh-puss neye-grih-cans) and Aspergillus niger (As-per-jill-us neye-jer), make black spores. Neurospora crassa (new-rah-spore-ah crah-sah) produces spores that appear pink. And the Penicillium (pen-ih-sill-ee-um) molds, the molds that make penicillin, are blue-green.
Some of the colors on your bread may be the result of growing colonies of bacteria, which also sometimes grow on old food. For example, a bacterium called Serratia marcescens (ser-ay-shuh mar-seh-sens) forms reddish colonies. You can tell bacteria colonies apart from molds because bacteria colonies appear smooth while molds look fuzzy.
Answer 4: Molds grow best in the dark, so not as much mold would be present on bread slices kept in a well-lit place.
Answer 5: Most fungi grow best around room temperature. But they can grow at a range of temperatures from cold (like in a refrigerator) to quite warm (body temperature). At temperatures colder or warmer than their favorite temperature, they usually do not grow as rapidly. If the temperature is too cold or too hot, they will not grow at all, and may even be killed.
The purpose of this project is to identify favorable conditions for fungi growth.
When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.
Temperature, moisture and light are independent variables that can be studied (one at a time) for their affect on the growth of fungi. Based on the variable that you choose to study its effects (independent variable), you must define all your other variables and constants.
For example when you study the effect of temperature on the growth of fungi, following are the variables:
Independent variable (also known as manipulated variable) is the temperature. This is the variable that we change in order to see how it affects the growth of fungi.
Dependent variable is the growth of fungi. The surface area covered by mold can be measured as a representative of fungi growth.
Constants are moisture, type of substrate (test sample) and method of experiment.
Controlled variable is light. We make sure that all samples are exposed to no light or the same amount of light.
Based on your gathered information, make an educated guess about what types of things affect the growth of fungi. Identifying variables is necessary before you can make a hypothesis.
My hypothesis is that a warm, moist and dark place is favorable for fungi growth.
This hypothesis is based on my personal observation on where mold and mildew is usually found at home.
Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control, you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”
Experiment 1: Test the effect of temperature on the growth of mold.
In order to determine the effect of temperature on the growth of mold, we will grow mold on identical pieces of bread in identical conditions, but in different temperatures. We measure the surface area covered by mold as a reference for the growth of mold.
- Using masking tape and marker, make labels for five sandwich bags. Label the first bag “1- Very Cold”, Label the second bag “2 – Cold”, the third “3 – Room Temperature/ Control”, the fourth “4 – Warm”, and the fifth “5 – Very warm”.
- Wash your hands. Place one slice of fresh white bread in each bag and seal the bags. Wrap each bag with a piece of aluminum foil or place each bag in a separate metal can and close the lid. Put another label on the aluminum foil or the can with the same writing as the labels of plastic bags.
- Place the bag labeled “Very Cold” in the freezer. Place the bag labeled “Cold” in the refrigerator, Keep the third bag “Control” at room temperature. Place the fourth bag in a “Warm” place, Place the fifth bag in a “Very warm” place.
See the notes below
- Once every 3 days open the aluminum foils or cans to see the condition of bread slices. Record your observations. If there any mold exists, estimate and record the surface area of the mold.
- In the 21st day, from the day you started your experiment, make your final observation. Measure the mold area as well as you can and record your results in a table like this
Mold Area at different days and temperatures
10ºF or -13º
40ºF or 5ºC
72ºF or 24ºC
90ºF or 32ºC
115ºF or 50ºC
1. The suggested temperatures are just a rough estimate. Your experiment temperatures may vary depending on the season and the equipment available to you.
2. A source of warm and very warm temperature can be an electric oven, a heat radiator, behind a refrigerator, or a heat lamp available at hardware stores.
In another experiment you may study the effect of light on growing mold. You may take three pieces of bread and keep one of them at normal light to be your control and place two others, one in a dark place, and the other exposed to more than normal light.
Yeast growth experiment
As you probably know from eating numerous meals, all breads are not the same. Tortillas and pitas are flat and dense, while loaves of sandwich breads and dinner rolls are puffy and lighter. In fact, if you look closely at a piece of sandwich bread, you can see a honeycomb texture in it where bubbles formed and burst. Why these differences? Aren’t all breads made of the same basic ingredients? What made those bubbles?
The differences are caused by a microbe called yeast, pictured here. Yeast is a kind of fungus. If you open up a package of baker’s yeast bought from the supermarket and sprinkle some out, you’ll see tiny brownish grains.
These are clumps of dehydrated yeast cells (dehydrated means most of the water has been removed). Let them sit there for a while and watch them and you’ll soon get bored. They don’t exactly do much, do they? But put them in bread dough and after a while you can definitely see that they must be doing something. But what exactly are they doing?
You’ll find out in this activity in which you’ll make your own bread dough.
Note: This activity can be done within one hour, though you could stretch it over a few hours if you wish, depending on how many different sweeteners you want to try.
- 2 cups of flour (plus a little extra)
- 4 medium-sized bowls
- 2 packages of rapid-rise yeast
- access to warm water
- 6 teaspoons of sugar
- a sweetener besides sugar such as honey or artificial sweetener
- 24 clear drinking straws (must be clear)
- 24 clothes pins
- measuring spoons
- ¼ cup measuring cup
- metric ruler
- permanent marking pen
- notebook and pen or pencil
- clock, watch or timer
What To Do:
1. Using the ruler, measure the point 3 centimeters from one end of each straw and mark that point with a line using the permanent marker.
2. Put ¼ cup of flour into each of your bowls. Mark the first bowl as the “Control.” Mark the others as 1, 2, and 3. (Just imagine that the dough in the illustration below is in four separate bowls.)
3. Measure 1 teaspoon of sugar and add it to the flour in the bowl marked 1. Put 2 teaspoons of sugar into bowl 2. Put 3 teaspoons of sugar into bowl 3.
4. Pour ¼ of a package of yeast (or ¼ teaspoon) into each of the four bowls. Using the spoon, stir together the ingredients in each bowl starting with the Control bowl.
5. Fill a cup with warm water from your faucet. The water should be warm, not hot and steaming. Dust your hands with a little flour. Carefully add the water to the Control bowl about a teaspoonful at a time and begin to knead the mixture. Your dough should eventually feel kind
of like Play-Doh—it should be damp, not wet. It’ll be sticky at first, but should eventually reach a point where it’s just damp enough that it no longer really sticks to the bowl or your hands. If it’s too sticky still, add a little bit more flour. Form the dough into a ball.
6. Repeat step 5 with each of the remaining bowls, working as quickly as you can. (If you have friends or classmates or parents helping out, each person should take a bowl and everyone should do step 5 at the same time.)
7. Working quickly, push three straws into the Control dough until the dough inside the straw reaches the 3-centimeter mark. Lay these straws by the Control bowl. Repeat this step with each of the remaining bowls.
Be sure to keep the straws beside the right bowls and don’t mix them up. (Again, if you’ve got more people working with you on this activity, each person should take a ball of dough and everyone should do this step all at the same time.)
8. Now pinch the bottoms of each of your Control dough straws, pushing the dough up from the bottom enough to clip a clothespin to the end of each straw. Mark the new height of the dough on each straw. Stand the straws upright using the clothespins as bases. Do the same with the rest of the straws. Label the batches of straws as Control, 1, 2 and 3.
9. Mark the time on your clock or watch or set your timer for 10 minutes. Wait 10 minutes. Then measure and mark the heights of the dough in each straw and record these heights and the time in your notebook. Repeat this step 10 minutes later. Repeat after another 10 minutes has passed.
10. During the 10-minute intervals while waiting for the dough in the straws to do its thing, discard your first batches of dough from each bowl and wash the bowls out. Dry them thoroughly. Be sure to keep an eye on the clock while you’re doing this so that you don’t miss the 10-minute deadline to check and measure your straws.
11. Repeat the dough making process only this time use a different kind of sweetener than sugar. Repeat the steps of filling and marking the straws. Label the new batch of straws and set them away from your first batch. Repeat the process of measuring the dough height in the straws at 10-minute intervals and recording the results in your notebook. Be sure to record the heights of this new batch of straws separately from the first batch.
12. Graph your results. First, calculate the average final height for each set of three straws in your first batch. Make a bar graph showing these average heights with the number of teaspoons of sugar (0, 1, 2, 3) on the horizontal axis and the height in centimeters on the vertical axis. Make a similar bar graph for your second batch of straws. See the sample graph on the right.
13. Throw away all the straws when you’re done. You might want to save the clothespins for another project in the future. Discard the dough in the bowls and wash them out. Clean up any spilled flour, sugar or yeast.
- In the first batch of straws you made, which straws showed the greatest change in dough height? Why?
- Can you guess what effect the sugar had and why?
- Did the Control dough rise at all or not? Why or why not?
- Did your dough made using a different sweetener besides sugar show the same results?
Answer 1: The straws containing dough from bowl 3 showed the highest rising. Since everything—the amount of flour, the amount of yeast, the temperature of the water—stayed the same except for the amount of sugar, you have probably already rightly guessed that the height of the dough rising is connected to the larger amount of sugar in this dough. Why is that? See the next question.
Answer 2: You will notice that the dough from the other bowls also rose some in their straws, the height connected to how much sugar was in the flour. The more sugar, the higher the dough rose. What can you figure out from this? Well, you’ve already read that yeast makes bread rise and become puffy instead of flat and this has something to do with yeast activity. What makes living things active? Food energy. The sugar is food for the yeast cells. The more sugar there is, the more active the yeast cells are.
Yeast cells chow down on the sugar molecules, breaking them apart in a chemical reaction and turning them into simpler elements and compounds including carbon dioxide. Carbon dioxide is a gas. Bubbles of carbon dioxide released by the yeast get trapped in the dough as bubbles. As more and more of these bubbles build up, the dough puffs up or rises. When the dough is put in the oven and baked, the carbon dioxide vaporizes in the heat, leaving spaces where the bubbles once and giving bread its honeycomb texture.
Answer 3: You probably saw some rising happen in the straws containing Control dough. This is because flour is a starch. Starches contain glucose, a form of sugar (this is why a saltine cracker tastes a little sweet if you let it sit on your tongue for a while; the enzymes in your saliva break the cracker starch down into glucose and other simpler molecules). So even though you didn’t add any sugar to the Control dough, it already contained some for the yeast to much on. However, because the amount of sugar in this dough was much less than in the others, less carbon dioxide could be made by the yeast in this batch and the dough couldn’t rise as much in comparison.
Answer 4: Different sweeteners will have similar or lesser effects on dough rising as sugar. You could try this experiment with as many different types of sweetening agents as you want to compare the results. Then you could do some research on the types of sugars in these different sweeteners to determine which ones work best as food for yeast.
Materials and Equipment:
Can be extracted from experiment design.
Results of Experiment (Observation):
Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.
No calculation is required for this project.
Summary of Results:
Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.
It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.
Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.
Related Questions & Answers:
What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.
If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.
If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.