Download Yeasts and Molds

Name ________________________________________
Date ___________
Yeasts and Molds. 2012
Activity: Yeasts and Molds
Goals:
1. To observe two types of microbial fungi: bread mold and yeast.
2. To determine the function of mold hyphae.
Background Information: Many of us are very familiar with macroscopic fungi – molds
and mushrooms. Yet, fungi are considered microbes. A slice of bread or a cup of yogurt
with mold growing on it is not very appetizing. Mold is a fuzzy, cobweb-like growth
produced on certain objects by several types of fungi. Like most fungi, molds use the
objects they live on as a food source. The microscope reveals the surprising structure of
mold – a twisted mass of thread-like structures called hyphae and tiny balloon-shaped
structures called fruiting bodies or sporangia. The mass of tangled hyphae is called
the mycelium.
Yeast cells are definitely microscopic. Nevertheless, yeast is visible in large quantities
when purchased for baking. Yeast can exist in a dormant or resting state for at least a
year. When provided with the right condtions – warmth, water, and a food source like
flour, the yeast cells “come alive.” They start feeding and producing waste products –
carbon dioxide and alcohol.
Fungi are important in the food industry. Yeast is used in baking and brewing. Some
molds are used to flavor the finest cheeses such as Camembert and Roquefort. How
can this be?
Materials: Prepared slide of bread mold (Rhizopus sporangia) and yeast cells
(Saccharomyces cerevisiae), foods with mold, Internet access, article on Penicillin
Procedure:
Rotate through the various stations listed below and complete the indicated activity
described at each station. Use your text book pages 95 -104, the handouts provided at
your stations and the hyperlinks throughout this document as resources for this activity.
Be sure to use complete sentences for all your responses.
Station 1: Bread Mold Slide
Drawing/Label a fruiting body
____ X
Station 2: Yeast
a. Drawing
_____ X
Station 3: The History of Bread Yeast
Yeast has been used since the “dawn of civilization.” Some scientists say that this
microbe was responsible for civilization! Read the article, The History of Bread Yeast
and write three facts about the history of yeast.
1.
2.
3.
Station 4: Food and Mold
Observe the examples of molds growing on the various foods at your station.
Illustrate two examples (Pictures of Molds on Food) of mold growing on the food
and write two facts based on the handout or hyperlink, Spoilage of Food.
Example 1: Drawing
Example 2: Drawing
Fact 1:
Fact 2:
Question: How is the structure of the hyphae well adapted for assisting the mold
in obtaining its food? (Hint: Use your text book to look up the function of hyphae.)
Station 5: Mold Website
Go to www.fsis.usda.gov/Fact_Sheets/Molds_on_Food/index.asp and answer the
following questions:
a. What parts does the body of many molds consist of?
b. Why are some molds dangerous?
c. Describe why some food molds are beneficial.
d. Name 2 ways you can use to protect food from mold.
Station 6: Penicillin Article
Read the article: Penicillin: the first miracle drug and answer the following questions.
The article can be found at: http://herbarium.usu.edu/fungi/FunFacts/penicillin.htm
a. The antibiotic, penicillin is isolated from what mold (scientific name)?
b. Who discovered the antibiotic properties of the mold that is used to make
penicillin?
c. Why was penicillin called a miracle drug when it was first discovered?