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

How Scientists Can Tell Good Bacteria from 

Harmful Bacteria   

DNA (deoxyribonucleic acid) is the “genetic blueprint” 

for all living things. A DNA molecule looks like a double 

helix that’s shaped like a long ladder twisted into a 

spiral. The ends are joined to form a continuous loop, 

like a rubber band. 

DNA contains the information that gives living  

organisms their traits or characteristics. In people, it 

determines traits like physical features, behaviors, and 

even whether we’re right or left-handed. In bacteria, 

the DNA molecule encodes the information that  

enables bacteria to grow, reproduce, and cause illness. 

Scientists use DNA “fingerprinting” to identify similar 

groups of bacteria. DNA is treated so that it exhibits 

its own special pattern. When there is an outbreak of 

foodborne illness, epidemiologists (scientists who track 

down the causes of diseases and find ways to control 

them) try to determine the source of bacteria in foods 

by examining the pathogen’s DNA “fingerprint.” Then 

they see if it matches up to “fingerprints” (patterns) 

from other samples. 

Bacteria mutating

DNA molecules

Howard Hughes Medical Institute

James A. Sullivan/ Cells Alive 

MODULE 1:

 Understanding Bacteria 

SCIENCE CONTENT

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