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

The 12 Most Unwanted Bacteria 

Campylobacter jejuni 

Clostridium botulinum 

Clostridium perfringens 

Escherichia coli O157:H7 

Listeria monocytogenes 

Salmonella Enteritidis 

Salmonella Typhimurium 

Shigella 

Staphylococcus aureus 

Vibrio cholerae 

Vibrio vulnificus 

Yersinia enterocolitica 

Magnified image of  

Campylobacter jejuni

Lan Hu, Ph.D., Dennis J. Kopecko, Ph.D., 

and Ben Tall, Ph.D.

Bacteria multiplying

James A. Sullivan/ Cells Alive

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FASCINATING FACTS

• 

Bacteria can multiply quickly — in fact, one cell can 

double within 20 to 30 minutes. 

• 

It takes less than 10 E. coli bacteria to make you sick. 

SCIENCE CONTENT

 

MODULE 1:

 Understanding Bacteria 

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11

MIDDLE LEVEL

Required Conditions for Bacterial Growth  

Time/Temperature

 — Under the right conditions, some bacteria can 

double their numbers within minutes and form toxins that cause illness 

within hours. To minimize bacterial growth in foods, it’s important to 

keep food temperatures below 40° F (4° C) or above 140° F (60° C). The 

level in between this temperature range is known as the Danger Zone. 

Nutrients

 — Bacteria need many of the same nutrients as humans in  

order to thrive (glucose, amino acids, and some vitamins and minerals). 

For example, bacteria grow rapidly in high-protein foods such as meat,  

poultry, eggs, dairy, and seafood. 

pH

 — Microorganisms thrive in a pH range above 4.6. That’s why acidic 

foods like vinegar and citrus juices are not favorable foods for pathogenic 

bacteria to grow; however, they may survive in these foods. 

Moisture

 — Most bacteria thrive in moist environments; they don’t grow 

on dry foods. That’s why dry foods like cereals can safely sit out at room 

temperature. 

Note: If dry foods like dry cereals or spices become contaminated from 

infected hands or equipment, bacteria can survive on the food and make 

people sick, but they can’t grow or multiply until the food is consumed.

Danger Zone

pH level

The 4 Cs of Food Safety 

MODULE 1:

 Understanding Bacteria

SCIENCE CONTENT