Science and Our Food Supply: Investigating Food Safety from Farm to Table

1. 

Isolate the sample. 

2. 

View the sealed dishes under a dissecting microscope 

or a hand magnifier. 

3. 

Consider the number of colonies and the diversity of 

the colonies. 

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21

MIDDLE LEVEL

MODULE 1:

 UNDERSTANDING BACTERIA

BACTERIA EVERYWHERE

(From The Big Picture activity)

1. 

How do bacteria multiply? (Bacteria multiply 

through a process called binary fission — 

where the cell’s DNA doubles. The cell splits 

and two independent cells are formed.) 

2. 

How fast can bacteria multiply? (Bacteria can 

multiply really fast — from a single cell to 

millions in 10 to 12 hours!) 

3. 

What’s the difference between an electron 

microscope and a light microscope?  

(Electron microscopes magnify far beyond 

what our light microscopes do. They  

magnify images up to a million times their 

actual size, and they use electrons instead of 

visible light to get magnified images.) 

4. 

In the video, why was Dr. X so concerned 

about what happened at the Barkley house? 

(The cutting board that Mr. Barkley used to 

prepare the raw poultry was not properly 

cleaned before Alex used it to cut up raw 

vegetables for the salad. Dr. X was  

concerned that the raw juices from the 

poultry could have contaminated the raw 

vegetables.) 

1. 

 How do you know the agar and swabs  

used to collect samples were free from  

microorganisms? (Make a control dish.)  

If the agar or swabs were not free from  

microorganisms, explain how this would  

affect your results. (Results could be  

misleading due to contamination.) 

2. 

What do the data you’ve collected have to  

do with the food you eat? (Bacteria are  

everywhere and can be transferred from  

surfaces to food and from hands to food.) 

3. 

Why do certain surfaces have more bacterial 

growth than others? (Bacteria thrive in certain 

environments depending on the moisture 

level, temperature, time, pH, etc.) 

4. 

How would you know if the organisms you 

observed were harmful or not? (You would 

need specific agars to grow and identify 

specific organisms, so in this lab you wouldn’t 

know.)