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Name: Namita
Status: Other
Grade:  Other
Location: IN
Country: United States
Date: August 2008

What does it mean when you find isolated bacterial colonies growing in a zone of inhibition?

There is variety in every population. In bacteria some differ in their tolerance for antibiotic. Most of the bacteria within the zone of inhibition have been killed or are being repelled from growing in the area of the antibiotic, but the ones you see are resistant to it. If you were to take one of those colonies and repeat the experiment, you would probably see that is no zone of inhibition because all of the offspring of those original bacteria are genetically the same as the original.


They are probably genetic mutants that are resistant to the antibiotic or contaminating bacteria that are not sensitive to the antibiotic.

Ron Baker, Ph.D.

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